Bird flu in humans – what does that mean?

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For the fourth time in a few months, a person in the United States has become ill with bird flu after coming into contact with an infected dairy cow – this time in the state of Colorado. As in the previous cases, the woman worked on a dairy farm with cows where the H5N1 virus was found, the health authority said. The patient showed only mild ocular symptoms and received antiviral medication. She has since recovered.

The H5N1 virus has been spreading more among birds for many years, now almost worldwide. In recent months it has been expanding more to mammals, including dairy cattle in the US. Researchers are more surprised and concerned. Questions and answers.

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What type of virus is it?

H5N1 is an influenza A virus similar to the seasonal influenza pathogens that circulate in humans. Since 1997, outbreaks caused by H5N1 have been recorded more, explains Martin Beer, Vice President of the Friedrich Loeffler Institute (FLI). As of 2016, a sub-variant of the pathogen, the so-called clade 2.3.4.4b, is spreading almost worldwide. The result was devastating outbreaks in wild birds, including poultry. Marine mammals, mink, foxes and bears were less commonly affected.

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How did the jump to beef happen?

According to the current information, the outbreak in cattle in the United States of America could be due to a single entry, explains expert FLI Beer. It is not clear how this transmission from wild bird to cow occurred. But researchers now know one thing: “If the virus gets into the uterus, it multiplies very quickly,” says Beer. This is also because of the receptors in the egg: They are perfect nesting points for the H5N1 variant – like the receptors in birds.

The egg is basically a chicken for the virus.

Martin Beer, Vice President of the Friedrich Loeffler Institute

Another dairy cow pathogen reaches through contaminated milking tools and is transported to new farms and regions. It is not yet clear whether the countermeasures in the US will take effect, Beer said. “The nightmare may be over in a while. If the virus isn’t already learning how to pass it efficiently from cow to cow through the nose.”

What does jumping on cattle mean?

According to Beers, 1.5 billion cattle are kept worldwide. If H5N1 resulted in a new global bovine flu, the risk to other farm animals would also increase – for example if pigs were fed contaminated raw milk. Furthermore, mammals are biologically closer to humans than birds. The risk of zoonosis – ie the risk of transfer from animals to humans – could be greater depending on the adaptations made.

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How do people get infected from cattle?

To date, four human cases have been recorded in the US related to the outbreak in dairy farming. Each time, one of the symptoms was conjunctivitis, Beer explains.

People keep track of bird flu receptors.

Martin Beer, Vice President of the Friedrich Loeffler Institute

For example, if a worker touches his eye while milking, he can contract the pathogen. Pasteurized milk is considered harmless, as confirmed by a study presented in the Journal of Virology.

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How does infection occur in humans?

Because subvariant 2.3.4.4b has been associated with much animal suffering, it is initially less harmful to humans than previously circulated forms of H5N1. The pathogen is highly adapted to birds, explains Beer. As of 2016, there have been fewer than 20 recorded and mostly mild infections in humans caused by viruses on this shore – with other variants there were hundreds before.

So the virus itself is more harmless to humans – and still not because it finds its way to mammals more often due to the huge number of infections in bird populations. They can be a kind of “mixer,” as Beer explains: If, for example, a mink or a pig is infected with different strains of influenza A, a new pathogen that is more dangerous to humans could emerge.

It is very important to have H5N1 on the radar.

Martin Beer, Vice President of the Friedrich Loeffler Institute

However, the “only” pathogen is in the middle range on risk lists for avian influenza zoonoses.

Would it be like the corona pandemic?

The chief virologist at the Berlin Charité, Christian Drosten, described H5N1 as a potential pandemic candidate for its spread in the US. Beer explains: “The situation is completely different than it is with Sars-CoV-2,” explains Beer. Influenza strains have been monitored for a long time. As a preventive measure, candidate vaccines are routinely defined for vaccination against potentially pandemic variants. 15 EU countries have recently ordered such a vaccine. Employees on Finnish fur farms are already being vaccinated as a precautionary measure.

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Source: dpa, AFP