Contagious with fur: avian flu in cats threatens the world with a new pandemic
The avian influenza virus from cats, which are now massively ill with this infection, is highly likely to spread to humans and cause a dangerous epidemic comparable to smallpox, Alexander Ginzburg, director of the N.F. Gamalei National Research Center for Epidemiology and Microbiology, told Izvestia. According to the expert, in case of such a development, a prototype vaccine should be created in the country, the production of which, if necessary, could be quickly adjusted. According to other scientists, animals can indeed serve as a convenient reservoir for the formation of new H5N1 strains dangerous to humans, but overcoming the interspecific barrier is a difficult task for the pathogen. It will probably be easier for the virus to reach humans through birds and pigs than through cats. Read more about the new threat in the Izvestia article.
The virus is more dangerous than smallpox
The probability of the avian influenza virus passing from cats, which are now massively infected in the United States and Europe, to humans is very high, Alexander Gintsburg, director of the N.F. Gamalei National Research Center for Epidemiology and Microbiology, told Izvestia. Given the contagiousness and severe clinical manifestations of this pathogen, the epidemic caused by it can be comparable to outbreaks of smallpox, the scientist said. Therefore, it is necessary to create a prototype H5N1 vaccine in Russia.
— We need a prototype of this vaccine. He must undergo the first and second stages of clinical trials against the strain, which is very likely to be transmitted not only between animals, but also from person to person. The mortality rate there is 50-70%, and with airborne transmission, smallpox will seem like a toy compared to what can happen as a result of one or two mutations," said Alexander Ginzburg.
A ready-made prototype of the vaccine should be available in case such a strain spreads in our country or other countries, so that within three to four weeks the drug can be developed throughout Russia and put into civil circulation. However, so far such work has not been carried out at the Gamaleya Center and there is no single state program that would combine the capabilities of developers and manufacturers of a promising vaccine, he added.
Epidemiologists have drawn attention to the active spread of the avian influenza virus among cats in Europe and the United States this spring. According to the European Food Safety Agency, more animals were exposed to the virus in the first three months of 2025 than in the previous nine months. Cats usually get sick by eating infected poultry or eggs. It is reported that individuals living on poultry farms in Belgium have been infected, which has led to paralysis, ataxia and other severe symptoms. As a result, the animals had to be euthanized. Similar cases have been identified in Iceland and Norway. The situation is similar in the USA.
The danger of the spread of the H5N1 virus among felines for humans is that animals serve as an excellent reservoir for the emergence of new strains of the pathogen that will be able to be transmitted to humans, said Mikhail Bolkov, a researcher at the Institute for the Study of Aging at the Russian Gerontological Research and Clinical Center of the Pirogov Russian National Research Medical University of the Russian Ministry of Health.
— The influenza virus moves between animals and humans cyclically. Being in animals, it can change its antigenicity, because they suffer from different strains than humans, and if different variants end up in the same cell, then a new genome can be assembled from different components. The genome of influenza viruses is segmented," he told Izvestia.
Cats have become an indicator of the spread of the virus among mammals. It is impossible to stop this process, and all that remains is to observe and prepare for possible problems, the specialist emphasized.
An epidemic among mammals
Researchers from the UK call the extent of the spread of avian influenza in the world a panzootie among mammals, which can contribute to human infection. They cite confirmed cases of mammalian-to-mammalian transmission of the virus on European fur farms, among marine animals in South America, and dairy cattle in the United States. According to their data, by the beginning of April this year, 70 human cases of avian influenza had been registered in the United States. 41 of them were associated with contacts with dairy herds, 24 with poultry farming, and two with interactions with other animals. The sources of three more infections remain unknown.
Experts estimate that H5N1 currently has a much lower potential for transmission than previous subtypes of human influenza that caused pandemics or seasonal outbreaks. And the virus is still poorly transmitted from person to person, but agricultural workers who often come into contact with animals remain a risk group.
It will be difficult for the H5N1 virus to overcome the interspecific barrier, although it has a high potential for mutations. If it can infect humans, it will most likely occur not through cats, but through birds or pigs, Elena Malinnikova, head of the Department of Virology at the Russian Ministry of Health, told Izvestia.
— From the point of view of overcoming the interspecific barrier, avian flu is closer to humans from birds and pigs than from cats. But it is very difficult to make such a transition of infection. At the same time, influenza viruses have a very high potential, because their RNA is not folded into a spiral, but has eight separate fragments. And they are characterized by reassortment — the "mixing" of different variants inside the cell. They can actually be transmitted from one species to another. In 2009, a triple reassortant appeared — pandemic H5N1, which infected birds, pigs, and humans. But there is no pathogen that could pass to humans from cats yet, and experts are not considering this possibility at the moment," the expert said.
If the avian influenza virus manages to overcome the interspecific barrier and infect humans, it will be able to spread actively among humans, but it is unlikely to have a catastrophically high mortality rate or symptoms comparable to smallpox, added Stanislav Stragnov, head of the Laboratory for the Analysis of public health indicators and digitalization of healthcare at MIPT.
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