Influenza D, a relatively recent addition to the alphabet of flu viruses, most commonly infects cattle. But experts have their eye on the threat it could potentially pose to humans.
Veterinarians first identified influenza D in pigs in 2011 and later sleuthed out the viruss primary host: cattle. Scientists have since been watching for any signs that this bovine flu is infecting humans, as flus from birds and pigs sometimes do. Theres currently no definitive proof, but there are worrying hints that human infection is possibleand that if luck favored the virus on a couple key fronts, it could begin spreading among people.
I think its fair to say that influenza D has everything it needs to infect humans from a scientific standpoint, says Feng Li, a virologist at the University of Kentucky, who helped identify the virus as a new type of influenza.
Scientists have identified four different types of influenza virus, most of which infect humans. The flu vaccines distributed in the U.S. each fall are tuned to two strains each of influenza A and B. Influenza C is very common but typically mild, except for some cases in infants, and there is no vaccine for it. Influenza D is the most recently identified type and the only one that has not been confirmed to infect humans.
Influenza D is believed to be most prevalent in cattle. A nationwide survey in 2014 and 2015 showed that about 75 percent of the animals carried antibodies to the virus. It seems to cause only mild bovine infection, says Mayara Maggioli, a veterinary immunologist at Oklahoma State University. Its a very subtle disease, she says. Its very well adapted. Infected cattle can have symptoms that arent so different from the flu we all know: runny noses or eyes, increased heart and breathing rates and a fever, cough or reduced appetite. Its very similar to what we see in humans, Maggioli says. Experiments have shown that inoculation can protect cattle from infection, but there is no commercially available vaccine for them.
Whether humans can be infected with influenza D is less clear. Theres evidence out there that suggests it might be happening, but its far from conclusive, says Richard Webby, a virologist at St. Jude Childrens Research Hospital in Tennessee. The data thats out there could go either way. NPR reported on the viruss potential to jump to humans last month.
Influenza D has scientists particularly concerned for people who spend long hours in close contact with cattle, especially in confined spaces. And recent research has found hints of the virus in this population. A 2022 study found viral particles on nasal swabs from cattle workers, but viruses can be present without actively infecting a person. A 2016 study found that cattle workers carried antibodies that reacted to influenza D, but influenza C is similar enough that antibodies for the latter can respond to the former as well, Webby says.
Although scientists have plenty of experience monitoring potential influenza spillover from animals, those efforts have focused on birds and pigsnot cattle. Thats because avian and swine influenzas have caused pandemics in humans, including the 1918 flu pandemic, which was caused by a virus that originated in birds, and the 2009 swine flu pandemic. Bovine viruses, as far as scientists know, have never wreaked such havoc. An avian influenza recently infected nearly 60 million poultry birds in the U.S. but has only infected one human, and no cases have been reported in humans in the U.S. since April 2022, according to the Centers for Disease Control and Prevention.
From the flu perspective, certainly cows have never really been thought about in studies of spillover, Webby says, although he notes that some groups are starting to investigate human-cattle interactions more closely. Its definitely an understudied interface. We absolutely need to know more about it.
If influenza D were to start infecting humans, the first sign would likely be respiratory symptoms in cattle industry workersand even the studies that show potential human immune reactions to the virus havent documented any sick workers. The second key piece of information would be if people with no direct interaction with cattle began to get sick, which would suggest the virus was spreading among humans.
Even if those two developments occurred, its not certain that influenza D would be disastrous among humans, especially given its relatively benign effects on cattle. In a human, I think probably, disease-wise, it should be mild, Li says. But as we all know, Mother Nature cannot be predicted.
All three experts Scientific American spoke with say theres no guarantee the virus wont eventually start infecting humans. Weve absolutely got to treat it with respect. Weve absolutely got to learn more about it, Webby says. You cant say theres no risk of this virus at all. I think that would be a naive statement.
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Scientists in China have identified strains of the influenza A-H3N2 virus circulating in dogs that might be gaining the capacity to spill over into humans.
Influenza-A viruses in animal reservoirs have repeatedly crossed species barriers to infect humans. H3N2 avian influenza or bird flu viruses were first transmitted to dogs around 2006 and have since formed stable canine lineages.
A team from the China Agricultural University analysed swabs from more than 4,000 dogs.
The findings, published in the journal eLife, showed that the H3N2 canine influenza viruses (CIVs) can recognise the human-cell receptors and hold the potential to replicate in humans.
"We found that, during adaptation in dogs, H3N2 CIVs became able to recognise the human-like receptor, showed gradually increased hemagglutination (HA) acid stability and replication ability in human airway epithelial cells," they wrote in the paper.
Further, they found that "human populations lack immunity to H3N2 CIVs, and even preexisting immunity derived from the present human seasonal influenza viruses cannot provide protection against H3N2 CIVs".
"Our results showed that canines may be intermediates for adapting avian influenza viruses to humans. Continuous surveillance coordinated with risk assessment for CIVs is necessary," the researchers said.
To evaluate the infectivity and transmission ability of H3N2 CIVs in dogs, the team deliberately inoculated six dogs with the known dog flu strains.
The dogs became mildly ill, with the most severe symptoms including fever, sneezing, wheezing, and coughing.
While so far, there is no human infection reported with the H3N2 CIVs, the team cautioned that "dogs might increase the opportunity of viral cross-species transmission to humans".
According to experts, the research highlights pet dogs' role as a possible "patient zero" for a future dog flu outbreak, The Telegraph reported.
It is "pretty clear" the bird flu H3 strain has become a dog-specific virus, Prof James Wood, the head of the department of veterinary medicine at the University of Cambridge, was quoted as saying.
"The changes in the canine virus apparently are making it better adapted to transmit within mammals, as you might expect after such a long period in dogs," he noted.
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The above article has been published from a wire source with minimal modifications to the headline and text.
Dog flu Is Mutating Into A Virus That Could Infect Humans, Chinese Scientists Warn Beware! Dog flu-causing virus is mutating and scientists in China believe that it has the ability to spill over into humans. Read on to know everything.
Are we not done with virus infections yet? From SARS-CoV-2 to Monkeypox, in the last 3 years, the world has battled several virus attacks. These viruses were all new to the environment and carry the ability to mutate and form new variants with more efficacy towards causing an infection. As the world continues to fight the virus attacks, Chinese scientists have issued a fresh warning against a new threat.
On Tuesday, Chinese scientists revealed that they have identified strains of the influenza A-H3N2 virus, which is currently circulating in dogs. And these strains have the ability to spill over into humans and cause virus infection, just like COVID and other viral illnesses. Speaking to the media, the scientists warned, "Humans could one day be struck down by 'dog flu' a mutated form of avian influenza which is slowly evolving."
In the study, a team of researchers in China analysed the swabs from more than 4,000 dogs. The findings, published in the journal eLife, stated that the H32 canine influenza viruses (CIVs) are mutating faster than usual and are able to recognise the human-cell receptors. This feature of the H3N2 canine virus makes it potential to replicate in humans.
In the published research paper, the scientists wrote: "We found that, during adaptation in dogs, H3N2 CIVs became able to recognise the human-like receptor, showed gradually increased hemagglutination (HA) acid stability and replication ability in human airway epithelial cells."
What is this H3N2 canine virus that scientists are warning humans about?H3N2 was discovered in dogs almost two decades ago. The virus infection can cause pooches to suffer from a runny nose and cough and can turn deadly in rare and extreme cases.
At a time when we are already dealing with rising COVID cases, the news about the certain worrisome mutation in the Dog flu-causing virus shouldn't be ignored. The reason why one should be aware of the infection is because of the fact that the human population lack immunity to the H3N2 CIVs, and even preexisting immunity gained from the present human seasonal influenza viruses cannot provide any protection against the H3N2 CIVs.
The H3N2 CIVs, also known as canine flu strains of H3N2 were first discovered in 2006. It has evolved from a strain of bird flu called H3N2. As per studies, the H3N2 CIVs can cause severe respiratory illnesses in dogs. Some of the serious symptoms associated with this virus are fever, sneezing, and coughing.
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The World Health Organization has elevated the fast-growing Omicron sublineage XBB.1.16 as a new variant of interest, and says it is outcompeting the previously dominant XBB.1.5 in many regions.
XBB.1.16 is a descendant of the recombinant XBB, which is a mashup of two BA.2 sublineages. On social media, the variant has been nicknamed Arcturus, like the brightest star in the northern celestial hemisphere. Currently, it is the dominant variant in India, where it is causing a wave of mostly mild illnesses. But it has been spotted in 32 other countries, including the United States.
This offshoot is very closely related to XBB.1.5. It has two gene changes that are different, including one in its spike protein, said Francois Balloux, director of the UCL Genetics Institute, at University College London, in a news release. Balloux said he expects it to do well in countries that didnt have a sizable wave of cases caused by the XBB.1.5 sublineage, like China and India. He says he doesnt expect it to have much impact on case numbers in the UK.
Studies have shown that whether a variant will cause a wave of cases in a country very much depends on the immunity in the population as well as the variant that was last the dominant cause of infections there.
WHO says that while this variant seems to be spreading faster than previous variants, and escapes immunity even in people whove recently had the XBB.1.5 strain it does not seem to be causing more severe illness. Therefore, WHO says the risk from this variant is low.
Last week in the United States, XBB.1.16 accounted for an estimated 10% of Covid-19 cases nationally, up from about 6% the week prior. The XBB.1.5 variant continues to be the dominant cause of new infections in the United States, according to data from the US Centers for Disease Control and Prevention.
WHO is recommending that countries share information about this variant, as well as conduct tests to see how well the immunity in their populations will defend against it. Its also asking countries to keep an eye on certain indicators of disease severity as this sublineage spreads.
