Photo showing the dorsal surfaces of a monkeypox case in a patient who was displaying the appearance of the characteristic rash during its recuperative stage. Photo: AFP
25,318 suspected cases of monkey pox, including 1,204 deaths, have been reported in the Democratic Republic of the Congo (DRC) since the declaration of monkey pox outbreak in December 2022.
The World Health Organisation (WHO) said on Tuesday.
According to the latest report, the outbreak, which was declared by the DRC Health Ministry on Dec. 16, 2022, was prompted by a notable surge in cases and fatalities associated with monkey pox as well as a fast spread to non-endemic provinces.
Since the beginning of 2024, a total of 5,133 suspected cases, including 321 deaths, have been reported, according to the WHO report. It warns that the current situation of the outbreak in the DRC is of grave concern due to the sustained increase in suspected cases compared to previous years.
It added that with a significant burden in younger populations, particularly children under 15 years of age, who constitute the majority of both suspected cases and deaths.
In April 2024, a high-level emergency regional meeting on monkey pox in Africa was convened in DRC capital Kinshasa, gathering 12 health ministers of regional countries, aiming to develop common strategies to prevent and intervene effectively in the face of monkey pox in Africa.
We must prevent the DRC from becoming the source of cross-border transmission, and our partnership must prioritise the health of those affected, said Jean Kaseya, the director general of the African Centers for Disease Control and Prevention (Africa CDC) at the meeting.
Over the years, monkey pox has become a real public health problem for our communities in the DRC, a regional threat and ultimately a global problem.
We must now mobilise to resolve this crisis, said Roger Kamba, DRC minister of public health, hygiene and prevention, said at the meeting.
Monkey pox, first detected in laboratory monkeys in 1958, is assumed to be transmitted from wild animals such as rodents to people or from human to human (Xinhua/NAN)
The OPINION / COLUMN is authored by independent contributors to the National Accord Newspaper. While contributors adhere to our editorial guidelines, they are not employed by the National Accord Newspaper. The perspectives and opinions expressed herein are solely those of the author and do not represent the views of the National Accord Newspaper or its staff.
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Since March, when the first reported cases of H5N1 bird flu began showing up in dairy cattle in Texas, the Food and Drug Administration has been asking farmers to discard any milk from infected animals. Initially, spotting tainted milk was believed to be fairly easy because cows that get sick with H5N1 begin producing milk that is thick and yellowish.
But in recent weeks, studies have found genetic traces of H5N1 in a large percentage of commercial milk products. Significant amounts of viral material from the avian influenza have also turned up in wastewater in Texas, specifically in areas where dairy processing plants are located. The presence of these viral fragments doesnt mean H5N1 is biologically active in these samples or capable of causing disease. All the evidence generated to date indicates that pasteurization is effective at inactivating H5N1 in milk, though the FDA continues to study the issue.
That is a huge relief. But it raises a big and important question: How is it that so much virus is getting off of affected farms and into the national milk supply in the first place? The most plausible and also the most concerning scenario is that visibly sick cows, the ones with strange looking milk and flu-like malaise, are just the tip of the outbreak.
Although theres little hard data at this point, scientists say the available evidence suggests that many more animals are likely being infected and producing virus-laced milk without any noticeable symptoms or changes to their milks color and consistency.
Further reading
Viral fragments in milk are likely from subclinically infected cows, Andrew Bowman, a veterinary epidemiologist at Ohio State University, told STAT. In a recent study of 150 commercial milk products representing dairy processing plants in 10 different states including Texas, Kansas, and others where herds have tested positive for H5N1 Bowmans team found viral RNA in nearly 40% of them.
A larger survey of 297 milk products, including cottage cheese and sour cream, conducted by the U.S. Food and Drug Administration, found viral RNA from the H5N1 bird flu in about 20% of samples.
The presence of viral genetic fragments is not believed to represent a risk to human health. Because pasteurization is a thermal process and doesnt involve the physical removal of any bacteria or viruses, the sensitive tests used for identifying DNA or RNA can detect dead genetic material left behind. Additional studies by both Bowmans team and FDA scientists found no evidence of infectious virus in the store-bought milk products sampled.
We were hoping all that milk was getting caught before it entered the supply system, said Andrew Pekosz, a molecular microbiologist who studies respiratory viruses at Johns Hopkins Bloomberg School of Public Health. Now were relying particularly on pasteurization to say the milk is safe.
There are a few other possible explanations for how virus-containing milk is getting off the farm. One is that farmers are simply ignoring the FDAs instructions to discard milk from infected cows. But farmers have strong incentives both in the interest of public health and their own economic outlook to not allow abnormal milk into bulk tanks. Human error or neglect could also be at play, but unlikely given that milk from clinically affected cows is so obviously abnormal.
An FDA spokesperson did not directly address questions about how H5N1 is winding up in the national milk supply. In a statement, the agency acknowledged the possibility that asymptomatic cows may be shedding virus and reiterated its stance that the dairy industry refrain from manufacturing or selling raw milk products. Given the detection of H5N1 in dairy cows is a novel and evolving situation, we are still learning about the dynamics of this particular virus, the statement said.
The FDA currently recommends that farmers discard milk only from symptomatic cows. The agency also has instructed farmers to take extra precautions, including heat-treating or pasteurizing milk, prior to disposing it or feeding it to calves or other farm animals. A recent investigation of outbreaks at dairy farms in Texas and Kansas found that at one farm where cats were fed unpasteurized milk from sick cows, about half the cats died after suffering neurologic symptoms.
A spokesperson for the U.S. Department of Agriculture referred questions to the FDA. In a technical note the USDA released on Tuesday, further clarifying a federal order to require testing of lactating dairy cows prior to interstate travel, the agency said it is not placing restrictions on the shipping or processing of milk from herds that have a non-negative test that is any result that is either presumptively positive, suspect, or otherwise not obviously negative.
The note reiterated the FDAs recommendations that producers discard milk from symptomatic cows. But crucially, milk from cows in the same herd that are not showing symptoms but may have been infected can be sent for processing under these rules.
Every tank of milk that travels from a dairy farm to a processor is sampled and screened for the presence of bacteria, antibiotics, and somatic cell counts. These are a measure of the immune cells that show up whenever a cow has an infection. Most dairy farmers receive an incentive bonus for better quality milk; the lower the somatic cell count, the higher the price it commands.
Given how the H5N1 virus is behaving in cows, with clear signs of infection in the udders, but little evidence of respiratory tract infections, its reasonable to believe somatic cell counts would be significantly elevated in sick animals, Terry Lehenbauer, a bovine disease epidemiologist and director of the Veterinary Medicine Teaching and Research Center at the University of California, Davis told STAT via email. The dairy farmer would be motivated to not allow abnormal milk from affected cows to go into the bulk tank.
Thats why he believes the most likely contributor to the problem is that there are infected dairy herds with asymptomatic animals producing H5N1-laced milk that looks normal. But with farmers reluctant to allow inspectors to test their cattle because of stigma and a lack of financial incentives to do so they cant know if their cows are the ones introducing the virus into the milk supply.
It is getting introduced, that much is clear. Not just from commercial milk testing, but also from analyzing whats flowing through city sewers.
About a year ago, researchers at Stanford University and Emory University developed a probe to detect H5N1 genetic material in city wastewater, to be ready just in case it jumped into humans. The work was part of WastewaterSCAN, a nationwide initiative to fish out fragments of RNA or DNA from viruses like SARS-CoV-2, human influenzas, and monkeypox from sewage, in collaboration with Verily Life Sciences. The probe hadnt yet been operationalized when the researchers began seeing unusual spikes in influenza A in parts of northern Texas in February, March and April of this year. Unusual because the human flu season had already mostly passed, and because the numbers were so huge.
Some of the concentrations we measured were among the highest overall influenza concentrations that weve ever measured as part of the program, said Marlene Wolfe, an environmental microbiologist and epidemiologist at Emory University and a co-principal investigator for WastewaterSCAN. Based on that aberration and the reports of H5N1 outbreaks in cattle, her team decided to go back and apply the probe to samples collected at three wastewater treatment plants two in Amarillo and one in Dallas dating back to February 4.
In a preprint posted last month, Wolfe and her team described what they found: large concentrations of the H5 gene ticking up in mid-March, at the same time the USDA was confirming the first outbreaks in dairy cows in the Texas panhandle. They also found that all three sewershed areas they tested were home to dairy processing facilities with permits to discharge milk byproducts into the sewers.
Such discharges are highly regulated and carefully monitored, with strict limits on volume, pH, and components such as fats, oil, and grease, Rachel Ravencraft, a spokesperson for the National Milk Producers Federation, said in an email. Thats because large influxes of milk, with its high concentrations of fat and protein, can overwhelm municipal wastewater treatment systems and mess with the microorganisms that break down sewage. In a typical processing environment, Ravencraft said, about 1% of fluid milk gets lost during normal operations, including cleaning and sanitizing equipment. No one just dumps a volume of milk down the drain.
That fits with what the Wastewater SCAN scientists think happened in North Texas. Our hypothesis is focused on the discharge of waste from facilities that are operating, for the most part, we believe, as expected, and that there is likely an H5 influenza that is part of that discharge, Wolfe said.
For now, its just a hypothesis, she emphasized. Wastewater surveillance cant determine the number of cases associated with those spikes, how many cows might be contributing to the uptick, or even what species is shedding this into the sewer. At this stage where we are sort of early still in this response, and theres not a lot of testing available, having the situational awareness about what is present in an area that we can get from wastewater and some information on trends, is useful.
One thing thats useful in this case, is the indication that there may have been additional unidentified outbreaks among cattle in the region with milk sent to these facilities since milk from infected animals is required to be diverted from the food supply.
Even though the measures of discarding milk and pasteurizing milk are not always perfect by themselves, Lehenbauer said, the combination of these actions together have provided strong evidence that our current milk supply is safe.
While the evidence so far supports the effectiveness of pasteurization, microorganism destruction depends on the combination of temperature and holding times in the pasteurizer as well as the specific properties of the pathogen and how many of them are present in the milk.
Higher levels of bacteria or viruses will take more time to kill. The FDA has been testing samples of raw milk trucked from farms to processing facilities to better understand how much virus the pasteurization equipment might encounter, officials told reporters at a briefing last week. That information will be used to inform additional experiments the agency plans to conduct to further validate the effectiveness of different pasteurization methods. The method used depends on whether the milk is intended for drinking, making cheese, yogurt, ice cream, or to be dried into powdered milk or baby formula.
Such studies are more important now than ever as its becoming increasingly clear that attempts to keep contaminated milk from reaching dairy processing plants are falling short.
Although public officials continue to stress that the bird flu virus currently poses a low risk to humans, they do worry about it spreading silently throughout the nations dairy cattle herds. If it were to become endemic in cows, the chances go up that it could mutate into a strain that could more easily infect people. And thats the scenario that keeps the nations top flu scientist up at night.
Science students around the world learn about Louis Pasteur's nineteenth-century discovery that heat destroys pathogens in food and beverages, reducing the risk of disease transmission. That breakthrough eventually led many countries to mandate pasteurization of certain products, including alcohol, fruit juice, and eggs.
Milk and other dairy products are also on that list, and their safety is of particular interest now due to the outbreak of H5N1, a strain of highly pathogenic avian influenza (HPAI), in U.S. dairy cows. As of May 6, the virus had been detected in 36 herds in nine states.
Experts have continued to emphasize the lack of any evidence or reason to believe that viable bird flu virus will get through pasteurization. On May 1, the U.S. Food and Drug Administration (FDA) released a statement reassuring the public that "preliminary testing did not detect any live, infectious virus" in fluid milk, cottage cheese, and sour cream. The tests "show that pasteurization is effective in inactivating HPAI."
It's understandable, though, that the public has been confused by mixed messaging from government officials and the media, including about genetic fragments of the virus initially recovered in pasteurized milk from supermarkets. That makes a clear explanation of the science, facts, and unknowns all the more pertinent.
Milk safety in the United States is regulated in part by the Pasteurized Milk Ordinance, a set of rules that dates to 1924. Centennial celebrations have been tempered somewhat by the current H5N1 outbreak, yet there is no reason to suspect that the pasteurization methods adopted a century ago are any less effective at preventing disease today, says Alex O'Brien, the dairy food safety and quality coordinator at the University of Wisconsin-Madison's Center for Dairy Research.
Experts have continued to emphasize the lack of any evidence or reason to believe that viable bird flu virus will get through pasteurization
The United States saw almost immediate public health returns after it adopted widespread pasteurization. In 1938, milk-borne illnesses accounted for 25% of all disease outbreaks attributed to contaminated food and water, but by 2014, that figure had declined to less than 1% (and of that 1%, the majority of cases70%were from raw, unpasteurized milk). Milk processing standards have become stricter over time, O'Brien says, and exhaustive federal and state regulations and standards now exist across production, processing, and packaging.
More than 90% of milk produced in the United States meets Grade A standards, meaning that it is sufficiently sanitary to be safely consumed as a beverage. Grade B milk, which constitutes most of the rest, can be used only to make certain dairy products, including ice cream, butter, and cheese.
Unlike sterilization, pasteurization does not eliminate every microbe a product may contain. Its primary purpose, instead, is to ensure that pathogens are destroyed with a 99.999% reduction. Pasteurization does this by heating products to a certain temperature for a certain time, the specifics of which are based on the biology of pathogen in question and the characteristics of the food or beverage being heated.
Generally, though, "anything can be inactivated by temperature, it's just a matter of how high and how long," says David Swayne, a Georgia-based poultry veterinarian who specializes in avian influenza, and the former director of the U.S. Department of Agriculture Southeast Poultry Research Laboratory.
H5N1 is an enveloped virus, meaning that it has a lipid-based outer wrapping that protects its genetic material and other essential components. Heat delivered through pasteurization dissipates this envelope and destroys some of the essential proteins in the virus's structure.
"The envelope just starts to melt away," says Erwin Duizer, a virologist at the National Institute for Public Health and the Environment in the Netherlands. "And if the envelope from a virus is basically gone, then the virus is not infectious anymore."
Plastic containers with milk are seen inside the El Elyon church, in El Paso, Texas, on March 17, 2021. REUTERS/Jose Luis Gonzalez
No data currently suggests that the H5N1 virus circulating in dairy cattle and found in infected cows' raw milk can survive pasteurization. Past pasteurization and cooking studies that Swayne and his colleagues conducted in chicken eggs and meat, for example, showed that heat treatment is effective at inactivating H5N1. The latter finding offers hope for ongoing testing for the possibility of H5N1 in beef.
On April 25, the FDA announced that it had detected genetic fragments of H5N1 in about 1 in 5 pasteurized retail milk samples from a nationally representative study. Swayne emphasizes that these results do not mean that viable virus had been found in milk. The pasteurization process inactivates viruses, but it does not remove their genetic material. What is left over, he says, is not "a whole virus that can infect someone."
This conclusion was supported by FDA testing of 297 retail dairy samples from 38 states that failed to detect any infectious virus, reaffirming "that the commercial milk supply is safe," the FDA wrote on May 1. The agency added that it will continue collecting samples and conducting studies "to further validate pasteurization."
Ongoing testing is warranted given the current outbreak, Duizer says, but he sees little cause for concern given pasteurization's proven track record. What's of more concern, he says, is "the ease with which this virus makes species jumps."
With the current information we have and the past 100 years of data from pasteurization, I have no concerns
"Things can change on a dime," O'Brien agrees. "But with the current information we have and the past 100 years of data from pasteurization, I have no concerns."
O'Brien says standards exist for pasteurization machinery, and are enforced stringently, to make sure the process is uniform across the industry. He says Grade A facilities are also randomly inspected each quarter by officials.
No evidence has been found so far of H5N1 infection in beef cattle, but continued testing is a good idea, Swayne says. If the virus does appear in beef cattle, it is unknown whether it would be present in their beef. Should that happen, though, Swayne reiterates that "cooking is highly effective at killing HPAI."
All that said, one group of consumers could be at higher risk of direct foodborne transmission of bird flu: those who drink raw, unpasteurized milk or who eat dairy products made from it.
Tests the FDA conducted of raw milk collected from infected cows confirmed that the samples contained high levels of viable H5N1 virus. Whether contaminated raw milk could lead to an infection in a person is unknown. But evidence is beginning to suggest that several domestic cats that lived on dairy farms were fatally infected this way.
Regardless of whether H5N1 can be transmitted to humans in raw milk, O'Brien warns that drinking it still introduces safety concerns: "Bacteria is everywhere, and cows can be carriers of things, too."
A cow and milking system are displayed at the Sunbelt Ag Expo, in Moultrie, Georgia, on October 18, 2022. REUTERS/Cheney Orr
Rachel Nuwer is a freelance science journalist and author who regularly contributes to the New York Times, Scientific American, Nature and more.
The World Health Organization (WHO) on Monday expressed concern about the outbreaks of avian flu detected on dairy cow farms in the United States. It is a cause for concern that the virus is infecting new species [of animals] and, with this, increasing the number of people exposed to the pathogen, said the agencys director for epidemics and pandemics, Maria Van Kerkhove.
A total of 36 farms in nine U.S. states have so far detected cases of avian flu in their herds. The outbreaks were discovered in March after investigations began in January, when several farms noticed a drop in milk production. The symptoms presented by the animals are very mild or almost undetectable. Although investigations are still open, these suggest that the origin of the infections are most likely wild birds that came into contact with livestock.
How the virus spreads between cows remains a mystery. It does not seem that transmission is through the usual forms of respiratory infections. Rather, it seems that some element used in milking the animals is what facilitates the spread of the virus, although for now these are hypotheses under investigation, said Richard Webby, the head of the WHO Collaborating Center for Studies on the Ecology of Influenza in Animals. The movement of livestock between farms would explain why the virus has been detected in dozens of farms. It is very likely that the number of farms with cases is greater than the [36] officially detected, he added.
So far, only one worker has been infected in connection with these outbreaks, a man from Texas who developed mild conjunctivitis-type symptoms, but not respiratory ones. The suspicion is that the virus got into his eyes when he scratched them with his infected hand after touching an infected cow.
The information offered at a meeting with experts and journalists on Monday reveals that the raw milk of affected animals has a high viral load, although the pathogens with the capacity to infect disappear with the pasteurization process. The WHO, like U.S. authorities, recommends not consuming milk or products made with raw milk, a minority but widespread practice in the country.
Available data also shows that up to 20% of tested milk on sale in affected states contains viral particles, although these are not infectious. The investigations carried out to date have not found viruses with the capacity to infect other products of animal origin such as meat and eggs in food sales circuits.
For now, the WHO continues to consider the risk to the general population low, and low to moderate for farm workers and other people exposed to livestock. Cats and raccoons infected with the virus have also been detected in farm environments.
Despite this, WHO officials are concerned about the danger posed by the presence of the virus in livestock. Although for now there is no data to indicate a greater risk for people, the fact that the pathogen is circulating and spreading in mammals close to humans increases the likelihood that it will develop mutations that allow it to adapt.
The virus causing the outbreaks is A(H5N1) clade (variant) 2.3.4.4b, which emerged in 2020 and quickly spread throughout most of the world through migratory birds, causing the death of hundreds of millions of the species since then. In these four years, viruses have also infected other mammalian species, increasing concerns among experts as to whether the mutations that make this possible could bring the pathogen closer to adapting to humans. For now, however, this clade has had almost no impact on people. The WHO only has 13 documented infections in humans, almost all of them mild or very mild.
In a risk report published on April 23 together with the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health, the WHO warned that Avian influenza A(H5N1) viruses, especially those of clade 2.3.4.4b, continue to diversify genetically and spread geographically, which, together with the jump to mammals, gives the pathogen increased opportunities for viral reassortment generating new genotypes with varied clinical signs. An example of this is the detection of a new form of influenza A(H5N1) virus in poultry in Cambodia, Laos and Vietnam.
The document notes that to date, there have been limited reports of transmission between mammals despite the increase in mammalian infections. It also states that although direct evidence is lacking, the large mortality of marine mammals, the infection in multiple fur animal farms in Finland and mink in Spain are consistent with mammal-to-mammal spread.
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Over a year ago, Marc Johnson, PhD, of the University of Missouri, developed a probe to detect H5 avian influenza A virus (IAV) genetic material in city wastewater because he expected it to start popping up in routine surveillancejust not from cattle.
"This cattle thing, that snuck up on us," he told CIDRAP News. "If this [probe] had been implemented nationally, we would've known about this in wastewater back in February, and they would have maybe gotten a lid on it sooner. It's really surprising that it became so widespread without anybody knowing."
But the probe wasn't operationalized at that time because H5N1 wasn't recognized until some cattle started showing symptoms in late March.
Wastewater surveillance begins at municipal wastewater treatment plants, which serve the vast majority of cities with populations above 10,000, Johnson said. In Missouri, for example, wastewater treatment plants serve roughly 60% of the population.
Treatment plant operators collect composite samples from the water every 15 to 30 minutes and send them to a lab, where they are concentrated and the viral RNA or DNA extracted for testing. The low-cost tests tell how much virus or viral fragments are present and identify the strains.
Influenza A virus, which infects both animals and people, has been responsible for all global flu epidemics. The highly pathogenic avian influenza (HPAI) strain of H5N1 emerged in the late 1990s, it began spreading widely in wild birds and poultry and also infected people.
In late March, the 2.3.4.4b H5N1 clade was discovered in cows with flulike symptoms. It had already been detected in wild birds, poultry, and some wild mammals in widespread outbreaks in the United States and other countries starting in 2022. In April, the US Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) released 239genetic sequences involved in the cow outbreaks.
Since then, viral H5N1 RNA (not infectious virus) has been detected in one in five US pasteurizedmilk samples (but notsour cream, cottage cheese, orground beef) in supermarkets. One case ofhuman infection (the second documented US case) was reported in a man who worked on a dairy farm. The man developed conjunctivitis but experienced no other symptoms and has since recovered. The previous human case involved a poultry worker in Colorado in April 2022.
Last month, Emory University researchers used a hydrolysis probe-based reverse transcription-polymerase chain reaction (RT-PCR) to measure H5 concentrations in wastewater dating back to February 4 at three sentinel Texas treatment plants near the H5N1 2.3.4.4b outbreak epicenter.
The plants (two in Amarillo and one in Dallas) were chosen from 15 facilities that showed a secondary onset of IAV in March and April, after the typical flu season. Industrial discharges containing animal waste, including milk byproducts, had been released into wastewater at the Amarillo facilities.
"If dairy industry activities in these sewersheds are a primary source of H5 in wastewater, this suggests that there are [sic] may be additional, unidentified outbreaks among cattle with milk sent to these facilities since milk from infected animals is required to be diverted from food supply," the study authors wrote.
H5 wasn't detectable before mid-March but then quickly reached similar concentrations as IAV M genesan indicator of influenza virus transmissibilitywhich were among the highest ever recorded in wastewater. At the same time, flu-related emergency department visits in the associated Texas public health regions were declining.
"These results suggest that wastewater monitoring is a viable method of monitoring certain animal pathogens, and can provide a leading edge of detection that is of particular importance for diseases with zoonotic potential like HPAI," the study authors wrote.
Michael Osterholm, PhD, MPH, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP), publisher of CIDRAP News, said testing wastewater systems that have no intake of animal-related sewage could serve as sentinels for human disease.
"There are those systems that have no animal input, so if they showed a spike, it could show evidence of human transmission," he said. He added that some systems like this may be testing for this now but that he hasn't seen the data yet.
Richard Webby, PhD, director of the World Health Organization Collaborating Centre for Studies on the Ecology of Influenza in Animals and Birds and a researcher at St. Jude Children's Research Hospital, in Memphis, Tennessee, said surveillance of both wastewater and supermarket milk samples is valuable. "It gives us a bit of a handle on whether the virus is changing as well without having to go into the contaminated environment of the farm," he said.
Surveillance at wastewater treatment plants serving meat-processing plants could also be useful, Johnson said. "We've seen this before, where we'll see viruses from animals being slaughtered showing up in the municipal wastewater," he said, adding that it could look for spillover to pigs or other animals. "The nice thing about thatit's kind of grossbut it doesn't matter which compartment the virus is in, it will end up in the wastewater."
Most respiratory viruses, such as SARS-CoV-2, which causes COVID-19, unlike enteric (intestinal) viruses, aren't infectious once they traverse the gastrointestinal tract because they are sensitive to changes in the level of acidity, Johnson said, adding that he has been unable to culture infective SARS-CoV-2 viruses from wastewater (see sidebar below).
It seems that the same is true for H5N1, which is also a respiratory virus.
A new study looking at the distribution of receptors that flu viruses can attach to in different cow tissues may help to explain the pattern of illness being seen in the outbreak of H5N1 bird flu in U.S. dairy cattle and also is sparking debate about the implications of the cow outbreak for human disease.
The study, a preprint that hasnt yet been through peer review by a scientific journal, found that tissue from the mammary gland contains abundant receptors of the kind to which avian flu viruses like H5N1 can attach. But brain and respiratory tract tissues contained far fewer of this type of receptor.
That fits with the description of how this virus is behaving in cows, with clear signs of infection in the udders, but little evidence of respiratory tract infections and no reports to date of cows experiencing neurological symptoms. This virus has been seen to attack the brains of a number of other mammalian species it can infect, including cats, which is why consideration of whether cows brains are also susceptible is important.
The work was done by scientists at the University of Copenhagen, Denmarks Statens Serum Institut, and St. Jude Childrens Research Hospital in Memphis, Tenn.
Further reading
The distribution of the receptor types some of which avian flu viruses can attach to, others to which human flu viruses attach raises concerns that cows could potentially give rise to a version of H5N1 or another novel flu virus that is able to transmit efficiently to and among people, the authors suggested.
These results provide a mechanistic rationale for the high levels of H5N1 virus reported in infected bovine milk and show cattle have the potential to act as a mixing vessel for novel [influenza virus] generation, they wrote.
Pigs, which can be infected with both bird flu and human flu viruses, have traditionally been referred to as mixing vessels for new viruses that could pose a pandemic threat. Thats because when an animal is co-infected with different flu viruses, the pathogens can swap genes, a process called reassortment. That phenomenon could give rise to new virus strains with enough human genes to be able to easily infect people, but also enough bird flu genes to be foreign enough to human immune systems that they could pose a serious risk to human health.
Cows have not been thought to pose such a risk. Though its known they can be infected with flu viruses, influenza hasnt been seen to be a major issue for cows. And until this outbreak, cows have not played a role in the H5N1 story.
This virus, first seen in China in 1996, is primarily one that infects wild birds and domestic poultry, though it has been shown to be able to infect numerous mammalian species over the nearly three decades that have followed. In that time, nearly 900 human infections have been detected. Of those people, roughly half have died.
In the current U.S. outbreak, one human case has been detected, a dairy farm worker in Texas whose sole symptom was conjunctivitis. Its widely believed there may have been other cases, but farmers have in many cases been unwilling to cooperate with health authorities trying to investigate the outbreak and many of the workers have been wary of cooperating as well.
Some scientists not involved in the research described the paper as interesting, but questioned whether one could conclude cows pose a mixing vessel risk based on these findings.
Malik Peiris, chair of virology in the University of Hong Kongs School of Public Health, told STAT in an email that previous research has shown that cows are not highly susceptible to human flu viruses. Furthermore, it would be hard to see how a human flu virus could reach a cows udder, which contains receptors for both avian and human flu viruses. Thus, I do not think the risk of human flu-H5N1 reassortment in cows is likely.
Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan, in Saskatoon, Canada, agreed, noting that knowing which tissues a flu virus can attach to only tells part of the story. There are other factors, she said, that determine whether or not a virus can replicate in the cells it attaches to, triggering infection.
That said, Rasmussen, who studies animal diseases that can jump into people, is still worried about H5N1 in cows. To date, H5N1 infections have been confirmed in 36 herds in nine states.
Im more concerned about cow H5 evolving toward human-to-human transmission by jumping between different hosts (bird to cow to human, cow to bird to cat, cow to cat) as well as cow to cow. This selects for viruses that can infect, replicate efficiently, and shed enough to transmit onward in many different hosts, and increases the odds that it could do so in a human one, she wrote in an email.
These data are confirmation to me that it is essential to get the cow outbreak under control, because there are many possibilities for a more transmissible human virus to emerge from it.
The Danish researchers took samples of stored tissues brain, respiratory tract, and mammary gland from a small number of cows and a calf. Some of the cows were dairy cows; others were beef cattle. They stained the tissue to see what receptors they had, whether they were for human or avian flu viruses, and among the latter whether they were the type best adapted for viruses that circulate among chickens or those that circulate in wild ducks. A spillover of virus from wild birds is believed to have started this outbreak in cows.
They found few receptors in the brain tissue they examined. What we found was that the influenza receptors were expressed in the neurons, but in a very low amount. So we also speculate that this could be the reason why there have not been found any neurological signs among infected cattle, said first author Charlotte Kristensen. Kristensen is defending her thesis this week and is set to begin postdoctoral research at the university, in the department of veterinary and animal sciences.
A surprising finding was a lack of receptors in the ducts of the mammary glands, which the authors said argues against the notion that cows are becoming infected by what they call an ascending infection. The leading hypothesis for how this infection is spreading among cows is that when an infected cow enters a herd, small amounts of its H5N1-contaminated milk can remain on milking equipment, coming in contact with the teats of uninfected cows, who then become infected.
Peiris, while agreeing the receptor pattern in the mammary ducts was surprising, said he still believes this route of infection is most likely, noting that there are reports that some cows only experience infection in some not all quarters of their udders. There is no other way to explain how one segment of the mammary gland is infected while others are unaffected, Peiris said.
Rasmussen agreed. These results are interesting and good to know. But I dont think they are sufficient evidence to rule out contaminated milking equipment or any other hypothetical transmission route. Especially respiratory, she wrote.
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Headlines are flying after the Department of Agriculture confirmed that the H5N1 bird flu virus has infected dairy cows around the country. Tests have detected the virus among cattle in nine states, mainly in Texas and New Mexico, and most recently in Colorado, said Nirav Shah, principal deputy director at the Centers for Disease Control and Prevention, at a May 1 event held by the Council on Foreign Relations.
A menagerie of other animals have been infected by H5N1, and at least one person in Texas. But what scientists fear most is if the virus were to spread efficiently from person to person. That hasn't happened and might not. Shah said the CDC considers the H5N1 outbreak "a low risk to the general public at this time."
Viruses evolve and outbreaks can shift quickly. "As with any major outbreak, this is moving at the speed of a bullet train," Shah said. "What we'll be talking about is a snapshot of that fast-moving train." What he means is that what's known about the H5N1 bird flu today will undoubtedly change.
With that in mind, KFF Health News explains what you need to know now.
Mainly birds. Over the past few years, however, the H5N1 bird flu virus has increasingly jumped from birds into mammals around the world. The growing list of more than 50 species includes seals, goats, skunks, cats, and wild bush dogs at a zoo in the United Kingdom. At least 24,000 sea lions died in outbreaks of H5N1 bird flu in South America last year.
What makes the current outbreak in cattle unusual is that it's spreading rapidly from cow to cow, whereas the other casesexcept for the sea lion infectionsappear limited. Researchers know this because genetic sequences of the H5N1 viruses drawn from cattle this year were nearly identical to one another.
The cattle outbreak is also concerning because the country has been caught off guard. Researchers examining the virus's genomes suggest it originally spilled over from birds into cows late last year in Texas, and has since spread among many more cows than have been tested.
"Our analyses show this has been circulating in cows for four months or so, under our noses," said Michael Worobey, an evolutionary biologist at the University of Arizona in Tucson.
Not yet. But it's a thought worth considering because a bird flu pandemic would be a nightmare. More than half of people infected by older strains of H5N1 bird flu viruses from 2003 to 2016 died. Even if death rates turn out to be less severe for the H5N1 strain currently circulating in cattle, repercussions could involve loads of sick people and hospitals too overwhelmed to handle other medical emergencies.
Although at least one person has been infected with H5N1 this year, the virus can't lead to a pandemic in its current state. To achieve that horrible status, a pathogen needs to sicken many people on multiple continents. And to do that, the H5N1 virus would need to infect a ton of people. That won't happen through occasional spillovers of the virus from farm animals into people.
Rather, the virus must acquire mutations for it to spread from person to person, like the seasonal flu, as a respiratory infection transmitted largely through the air as people cough, sneeze, and breathe. As we learned in the depths of COVID-19, airborne viruses are hard to stop.
That hasn't happened yet. However, H5N1 viruses now have plenty of chances to evolve as they replicate within thousands of cows. Like all viruses, they mutate as they replicate, and mutations that improve the virus's survival are passed to the next generation. And because cows are mammals, the viruses could be getting better at thriving within cells that are closer to ours than birds."
The evolution of a pandemic-ready bird flu virus could be aided by a sort of superpower possessed by many viruses. Namely, they sometimes swap their genes with other strains in a process called reassortment. In a study published in 2009, Worobey and other researchers traced the origin of the H1N1 "swine flu" pandemic to events in which different viruses causing the swine flu, bird flu, and human flu mixed and matched their genes within pigs that they were simultaneously infecting. Pigs need not be involved this time around, Worobey warned.
Not yet. Cow's milk, as well as powdered milk and infant formula, sold in stores is considered safe because the law requires all milk sold commercially to be pasteurized. That process of heating milk at high temperatures kills bacteria, viruses, and other teeny organisms. Tests have identified fragments of H5N1 viruses in milk from grocery stores but confirm that the virus bits are dead and, therefore, harmless.
Unpasteurized "raw" milk, however, has been shown to contain living H5N1 viruses, which is why the FDA and other health authorities strongly advise people not to drink it. Doing so could cause a person to become seriously ill or worse. But even then, a pandemic is unlikely to be sparked because the virusin its current formdoes not spread efficiently from person to person, as the seasonal flu does.
A lot! Because of a lack of surveillance, the U.S. Department of Agriculture and other agencies have allowed the H5N1 bird flu to spread under the radar in cattle. To get a handle on the situation, the USDA recently ordered all lactating dairy cattle to be tested before farmers move them to other states, and the outcomes of the tests to be reported.
But just as restricting COVID tests to international travelers in early 2020 allowed the coronavirus to spread undetected, testing only cows that move across state lines would miss plenty of cases.
Such limited testing won't reveal how the virus is spreading among cattleinformation desperately needed so farmers can stop it. A leading hypothesis is that viruses are being transferred from one cow to the next through the machines used to milk them.
To boost testing, Fred Gingrich, executive director of a nonprofit organization for farm veterinarians, the American Association of Bovine Practitioners, said the government should offer funds to cattle farmers who report cases so that they have an incentive to test. Barring that, he said, reporting just adds reputational damage atop financial loss.
"These outbreaks have a significant economic impact," Gingrich said. "Farmers lose about 20% of their milk production in an outbreak because animals quit eating, produce less milk, and some of that milk is abnormal and then can't be sold."
The government has made the H5N1 tests free for farmers, Gingrich added, but they haven't budgeted money for veterinarians who must sample the cows, transport samples, and file paperwork. "Tests are the least expensive part," he said.
If testing on farms remains elusive, evolutionary virologists can still learn a lot by analyzing genomic sequences from H5N1 viruses sampled from cattle. The differences between sequences tell a story about where and when the current outbreak began, the path it travels, and whether the viruses are acquiring mutations that pose a threat to people. Yet this vital research has been hampered by the USDA's slow and incomplete posting of genetic data, Worobey said.
The government should also help poultry farmers prevent H5N1 outbreaks since those kill many birds and pose a constant threat of spillover, said Maurice Pitesky, an avian disease specialist at the University of California-Davis.
Waterfowl like ducks and geese are the usual sources of outbreaks on poultry farms, and researchers can detect their proximity using remote sensing and other technologies. By zeroing in on zones of potential spillover, farmers can target their attention. That can mean routine surveillance to detect early signs of infections in poultry, using water cannons to shoo away migrating flocks, relocating farm animals, or temporarily ushering them into barns. "We should be spending on prevention," Pitesky said.
No one really knows. Only one person in Texas has been diagnosed with the disease this year, in April. This person worked closely with dairy cows, and had a mild case with an eye infection. The CDC found out about them because of its surveillance process. Clinics are supposed to alert state health departments when they diagnose farmworkers with the flu, using tests that detect influenza viruses, broadly.
State health departments then confirm the test, and if it's positive, they send a person's sample to a CDC laboratory, where it is checked for the H5N1 virus, specifically. "Thus far we have received 23," Shah said. "All but one of those was negative."
State health department officials are also monitoring around 150 people, he said, who have spent time around cattle. They're checking in with these farmworkers via phone calls, text messages, or in-person visits to see if they develop symptoms. And if that happens, they'll be tested.
Another way to assess farmworkers would be to check their blood for antibodies against the H5N1 bird flu virus; a positive result would indicate they might have been unknowingly infected. But Shah said health officials are not yet doing this work.
"The fact that we're four months in and haven't done this isn't a good sign," Worobey said. "I'm not super worried about a pandemic at the moment, but we should start acting like we don't want it to happen."
2024 Kaiser Health News. Distributed by Tribune Content Agency, LLC.
A bird flu strain that began circulating in 2020 continues to evolve globally and locally within the United States. If you're wondering what this means, understanding the basics what bird flu is, how it spreads, whether foods are safe, and prevention tips can help. More information will come in as scientists learn more, so stay tuned.
Bird flu, or avian flu, is a naturally occurring illness. Just as certain flu viruses spread among humans, Type A influenza viruses often spread among wild birds. The strain of virus circulating now is H5N1, named for two proteins on its surface.
Avian flu infections are highly contagious. Infection often spreads first among wild water birds, such as ducks, geese, and gulls, and shore birds, such as plovers and sandpipers. The viruses are carried in their intestines and respiratory tract and shed in saliva, mucus, and feces. Wild birds can easily infect domestic poultry, such as chickens, turkeys, and ducks.
Some bird species, including ducks, may carry and spread infection without appearing sick. Domestic flocks are more likely to sicken and possibly die from bird flus. However, not all avian flu viruses are equally harmful:
Yes, though this doesn't usually happen.
When flu viruses mutate, they may be able to move from their original hosts birds in this case to humans and other animals. At this writing, two cases of bird flu in humans have been reported in the US since 2022.
The virus may be introduced into the body through the eyes, nose, or mouth. For example, a person may inhale viral particles in the air (droplets, tiny aerosolized particles, or possibly in dust). Or they might touch a surface contaminated by the virus, then touch their eyes or nose. Bird flu in humans typically causes symptoms similar to seasonal flu, such as fever, runny nose, and body aches.
A surprisingly long list of animals affected by the current H5NI bird flu infection includes:
It might seem odd that there's been so much concern and news coverage about bird flu lately. After all, bird flu has been around for many years. We've long known it sometimes infects nonbird animal species, including humans.
But the current outbreak is unique and worrisome for several reasons:
Public health officials emphasize that the food supply is safe.
But concern has understandably run high since the discovery that this outbreak has spread from birds to dairy cows for the first time. More alarming? A study found fragments of bird flu DNA which is not the same as live virus in 20% of commercially available milk in the US.
So far, there's been no indication that bird flu found in pasteurized milk, beef, or other common foods can cause human illness. Even if live bird flu virus got into the milk supply, studies show that routine pasteurization would kill it. Initial tests did not find the virus in ground beef.
Of course, if you are particularly concerned, you could avoid foods and beverages that come from animals affected by bird flu. For example, you could switch to oat milk or almond milk, even though there's no convincing scientific justification to do so now.
Bird flu rarely spreads to pets. While that's good news, your pets could have exposure to animals infected with bird flu, such as through eating or playing with a dead bird. So, it's safest to limit your pet's opportunities to interact with potentially infected animals.
If you work with animals, especially birds or livestock, or hunt, the Centers for Disease Control and Prevention (CDC) recommends precautions to minimize your exposure to bird flu.
The CDC recommends everyone take steps to avoid exposure to bird flu, including:
Right now, available evidence doesn't support more dramatic preventive measures, such as switching to an all-plant diet.
Despite all the worrisome news about bird flu, this recent outbreak may wind up posing little threat to human health. Virus strains may mutate to spread less efficiently or to be less deadly. Efforts are underway to contain the spread of bird flu to humans, including removing sick or exposed animals from the food supply and increased testing of dairy cattle before transport across state lines.
And there is other encouraging news:
Though there's much we don't know, this much seems certain: bird flu will continue to change and pose challenges for farmers and health experts to stay ahead of it. So far, public health experts believe that bird flu poses little health risk to the general public.
So, it's not time to panic about bird flu. But it is a good idea to take common sense steps to avoid exposure and stay current on related news.
For updated information in the US, check the CDC website .
So far, one human case has been reported in the United States since the outbreak of bird flu among the millions of dairy cattle across the country. At least 220 people are subject to monitoring and at least 30 have been tested.
However, many more people have been exposed to infected animals, and it is important that all those exposed are tested or monitored and receive care if needed, Tedros Adhanom Ghebreyesus, Director-General of the UN World Health Organization (WHO), said at his regular press briefing.
So far, the virus does not show signs of having adapted to spread among humans, but more surveillance is needed, he urged.
The WHO chief also said that though the virus has been detected in raw milk in the US, preliminary tests show that pasteurisation kills the virus.
WHOs standing advice in all countries is that people should consume pasteurised milk, he highlighted.
Pasteurisation is a heat treatment process for milk that reduces the numbers of possible pathogenic microorganisms to levels at which they do not represent a significant health hazard. It also extends the usable life of milk.
Tedros also noted that based on the available information, WHO continues to assess the public health risk posed by H5N1 avian influenza to be low and low-to-moderate for people exposed to infected animals.
He added that the agency has a system for monitoring influenza globally through a network of centres in 130 countries, seven collaborating centres and 12 reference laboratories with the capacities and biosafety requirements to deal with H5 viruses.
We also have the Pandemic Influenza Preparedness Framework to support the rapid development and equitable distribution of vaccines in case of an influenza pandemic, he said.
In recent years, H5N1 has spread widely among wild birds, poultry, land and marine mammals and now among dairy cattle.
Since 2021, there have been 28 reported cases in humans, although no human-to-human transmission has been documented.
The outbreak in the United States has so far infected 36 dairy herds in nine states.
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