Virologist Warns: When Bird Flu Can Become Dangerous

Since the beginning of the week, "increased risk" regarding avian flu applies to all of Austria. The highly pathogenic H5N1 flu virus has now caused enormous ecological and economic damage worldwide - an "imminent pandemic" among humans is currently "unlikely," explained virologist Florian Krammer on Monday afternoon during a symposium of the Agency for Health and Food Safety (AGES).

New Variant Circulating Among Animals

Fortunately, the virus, which is circulating mainly among wild animals and for some time also among livestock, is probably not yet being transmitted from human to human. The currently globally circulating avian flu virus is, according to Krammer, a "very fit" new variant, designated "Clade 2.3.4.4b," which emerged in 2020. For the virologist working at the Ignaz Semmelweis Institute in Vienna and the Icahn School of Medicine at Mount Sinai in New York (USA), the current situation is a prime example of "One Health" - the comprehensive consideration of human and animal health. This concept is also the theme of the AGES event, which ends on Tuesday.

When Variants Jump, It Can Become Dangerous

One must "keep an eye on" the development of H5N1, emphasized Krammer. This is because the larger influenza pandemics of the past more than 100 years, with millions of human deaths, have always occurred when a descendant of "Influenza A," such as H5N1, has jumped from animals to humans. Many subtypes of such pathogens circulate in animals overall. Reservoirs mainly include seabirds, bats, but also mammals and livestock. It becomes problematic when there is a lot of genetic exchange between humans and animals and a lot of human-animal interaction.

It could become particularly dangerous if humans are simultaneously infected with seasonal flu viruses and H5N1, contracted through direct animal contact. If the genetic material of these two variants mixes in a very unfavorable way - if a new variant, so to speak, takes on the danger and transmissibility of avian flu and additionally the good adaptation to humans or mammals of the seasonal viruses - then one would be dealing with a "dangerous situation" that has historically led to pandemics, said Krammer.

Seasonal Vaccines Could Be Quickly Adjusted

Fortunately, there have been few confirmed infections in humans so far, especially in Europe, most of which have been mild. However, a continuing problem is that H5N1 has made the jump to cows in North America, which is "still not under control" there. The virus primarily infects the mammary glands and reaches particularly high concentrations there. In its inactivated form, it has also been found in milk in the USA for some time.

It cannot be completely ruled out that human-to-human transmission of H5N1 has already occurred in North America, Krammer said. However, confirmation is still pending. If there were more bird flu infections among humans, something could certainly be done: The drugs Baloxavir and Tamiflu should be helpful here. According to Krammer, the common seasonal flu vaccines could also be relatively quickly adjusted to H5.

Influenza Vaccination Recommended for Close Animal Contact

People who have a lot of contact with vulnerable animals, such as veterinarians, poultry farmers, and hunters, should definitely consider getting vaccinated against seasonal influenza this year. Additionally, there is already "the possibility for people in risk groups to immunize themselves with an H5 vaccine" in Austria, the virologist said before the conference to APA-Science: "This naturally also protects against such infections." A vaccine is also available for chickens. "It is successfully used in France, for example," Krammer said.

(APA/Red)

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