Dozens of cats in Poland die from bird flu, World Health Organization puts society on alert

The World Health Organization (WHO) raised concerns about the spread of bird flu cases in mammalian populations a month after an unusual outbreak of bird flu was detected in several parts of Poland and killed dozens of cats. This risk could lead to the spread of bird flu. Make it easier for viruses to adapt to humans. “Infections in these animals have been documented in the past, but this is the first incident of a large number of affected cats over a broad geographic area. WHO is monitoring the situation closely with its partners and the Polish government,” said the organization’s director-general. Tedros said last Wednesday.

“This is a very unique episode. This is the first time that cases have co-occurred in mammals in areas that are far from each other, which is in stark contrast to what has been observed so far, where cases have been concentrated in farms or Among animals in natural spaces, this makes us suspect a common source of “contagion,” explains Inmaculada. Casas is head of respiratory viruses at the National Center for Microbiology (CNM) and director of influenza surveillance at WHO in Spain.

“The size of the outbreak and the geographic distribution of the cases is very important,” said Richard Webby, director of the World Health Organization’s Center for Poultry Pathology Research. We can’t say for sure whether cat infections make it easier for the virus to spread to humans, but we have to be concerned about these infections in mammals, and this outbreak is particularly severe.” related. “

While there have been other outbreaks of bird flu in mammals last year—Finland recently reported outbreaks in 10 fox fur farms this month—the outbreak in Polish cats is puzzling for several reasons indivual. The first is its size: 61 animals died of natural causes or were euthanized, of which 34 (54%) tested positive for the virus. The second is its extension, since the cats live in different parts of the country and in very different living conditions: of the 25 cats for which information is available, two are stray cats and 18 are domestic cats with access to balconies, patios Or patio, and 5 just house cats. Unable to access external. In the end, Polish authorities failed to find the source of the infection after a month-long investigation. There have been no known cases of transmission of the virus between cats.

The World Health Organization report states that “possible sources of infection are diverse, including direct or indirect contact with sick wild birds and consumption of contaminated pet food.” This last hypothesis has been defended by several experts, although it cannot Explained all the cases, also not confirmed. Contact with wild birds explains some infections, but not most. That fact, along with the fact that neighboring countries have yet to detect similar incidents, adds further problems to the outbreak.

The owners of the infected animals have not been infected, leading the World Health Organization not to revise the risk rating for the current situation. The numbers remain “low” for the general population and “low to moderate” for people who live with affected cats, and for professionals who come into contact with sick animals, such as veterinarians. “.

unprecedented expansion

The outbreak has brought renewed attention to the unprecedented two-year spread of bird flu.In a recently published study nature, Richard Webby noted that a new clade (a variant) of the pathogen, 2.3.4.4b, became more infectious sometime in 2021 and has become the majority in most parts of the world due to the impact of migratory birds. Tens of millions of birds and thousands of mammals have died in Europe, Asia, the Americas and Africa in two years.

The virus is the one found in cats in Poland and is also responsible for thousands of outbreaks in wild and farmed birds on four continents. It also led to high mortality of mink on fur farms in Galicia last October and killed thousands of marine mammals in the American country. The virus has also been found in dead seals in Scotland and dogs on Italian farms hit by bird flu outbreaks.

The key question for scientists and researchers is whether these events will bring the world closer to the next pandemic. The adaptation of the virus to mammals will be the first step, but it is only half done: it can infect mammals, but not spread between them. According to published research, to date all affected animals in this class became infected through ingestion or close contact with sick poultry. Only on farms in Galicia have there been indications of transmission between mink, although this incident ended with the sacrifice of all animals.

However, this could change, and close monitoring of diseases around the world is the only way humans can protect themselves in the face of uncertainty. Tim Uyeki, medical director of the flu division at the Centers for Disease Control and Prevention (CDC), thinks so. “As more birds and mammals become infected, so does the opportunity for the virus to evolve. To date, there is no evidence that it spreads in any mammal in a sustained manner, but if that happens , the threat to public health will increase,” he insisted in a written response to the newspaper.

To date, only a dozen people worldwide have been diagnosed with infections caused by clade 2.3.4.4b, two of whom developed severe clinical manifestations. Compared with other recent variants, this branch of the virus has almost zero impact on humans. Between 2006 and 2016, Egypt recorded 356 cases and 121 deaths (34% fatality rate), according to available data from the World Health Organization and others, and Indonesia reported 189 infections and 157 deaths a decade earlier ( 83% mortality rate). organism.

“The number of cases registered in the population is very low. The virus does not appear to be well adapted to humans, as evidenced by the fact that large outbreaks in farms and other settings have caused little transmission among exposed populations,” said Inmaculada Casas.

A girl was infected in January

In January, a girl was hospitalized in Ecuador after being infected by her family’s poultry, one of only two serious cases registered so far. The few diagnoses made so far have also turned out to be false positives, due to contamination of samples from routine testing of poultry farm workers affected by the outbreak (two of them in Guadalajara last year).

“We still don’t know why the virus is not contagious to humans, and more research is needed. These changes make it well adapted to birds, but may have made it less efficient at infecting humans,” Richard said. Webby said.

Still, Tim Uyeki warned that the world must remain vigilant about the virus’s ability to mutate. “Like all influenza A viruses, the current form is still evolving and may undergo genetic recombination. Surveillance of cases in wild birds, poultry, mammals, and humans around the world is critical to assessing changes that may increase threats to public health Crucial.”

The bird flu virus is one of more than a dozen pathogens with pandemic potential that the World Health Organization is monitoring. This is the first leg of a strategy that the organization and other international organizations have been insisting on, in which vaccines and antiviral drugs form another pillar. According to Inmaculada Casas, this arsenal could allow the world to better deal with a hypothetical pandemic caused by an influenza virus than against a coronavirus.

“The big difference with SARS-CoV-2 is that for bird flu, we already have vaccine candidates from the clade that is currently circulating. It will be very easy and faster to make a vaccine. Plus, we have effective treatments, such as Oseltamivir. The influenza surveillance system established by the World Health Organization in 1952 has allowed us to accumulate a great deal of experience that will allow us to identify and adequately respond to any future threats”, concludes Inmaculada Casas.