Avian flu: WHO fears that the virus adapts "more easily" to the human species

The World Health Organization on Wednesday expressed concern that increasing cases of bird flu in mammals could help the virus spread "more easily" to humans.

"Bird flu viruses normally spread among birds, but the increasing number of cases of H5N1 avian flu being detected in mammals - which are biologically closer to humans than birds - raises concerns that the virus may be adapting to more easily infect humans,” the WHO said in a statement.

In the warning - also signed by the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health (WHO), the organizations call on countries to work together "to save the greatest number of animals possible and to protect populations". Since its appearance in 1996, the H5N1 avian influenza virus has caused essentially seasonal epizootics. But according to the WHO, since 2020, a variant of this type of virus has caused an unprecedented number of deaths among wild birds and poultry in many countries in Africa, Asia and Europe.

In 2021 the virus spread to North America and in 2022 to Central and South America. These epizootics are synonymous with massive deaths of wild birds and the slaughter of tens of millions of poultry. "There has been a recent paradigm shift in the ecology and epidemiology of avian influenza, which has heightened global concerns," said Dr Gregorio Torres, chief scientific officer of OMSA, in press release on Wednesday. He notes that the disease has spread to new regions and caused unusual mortality in wild birds, as well as “an alarming increase in the number of cases in mammals”.

The three organizations are also concerned that certain mammals could serve as "mixing reservoirs" for influenza viruses, leading to the emergence of new viruses that could be even more dangerous to animals and humans. Recently, there have been increasing reports of fatal outbreaks in mammals, they say. Since 2022, ten countries across three continents have reported outbreaks in marine and land mammals to OMSA, but the organizations believe it is likely that outbreaks have not yet been detected or reported in other countries. Avian influenza has so far been detected in at least 26 species of mammals, including farmed mink and seals, but also in domestic animals such as cats and dogs.

According to the WHO, human infections can cause serious illness with a high mortality rate. The human cases detected so far are mainly the consequence of close contact with infected birds or with contaminated environments. “Based on the information available so far, the virus does not appear to be able to transmit easily from person to person, but vigilance must be maintained to identify any evolution of the virus that could change this,” said Dr. Sylvie Briand, Head of Epidemic and Pandemic Preparedness and Prevention at WHO. “We encourage all countries to improve their ability to monitor these viruses and detect any human cases. This is all the more important since the virus is now affecting countries which have limited experience in the surveillance of avian influenza”, she continues.