Questions and answers Will bird flu become the next pandemic?

Bird flu has been rampant among birds for a long time. Cattle have been spared - until now. How great is the risk to humans? And is the next pandemic just around the corner? Answers to the most important questions.

The number of cattle infected with bird flu is increasing in the USA. According to the US health authority CDC, there are now more than 130 recorded H5N1 infections in a dozen US states. This development is causing increasing concern among experts. The answers to the most important questions.

What kind of virus is it?

H5N1 is an influenza A virus like the seasonal flu pathogens that circulate in humans. H and N refer to two proteins in the viral envelope: haemagglutinin and neuraminidase. They occur in different subtypes (in birds H1 to H16 and N1 to N9). The name H5N1 therefore means the combination of the H5 and N1 proteins on the surface of the variant.

Why is everyone talking about bird flu at the moment?

The H5N1 virus has been increasingly affecting birds for decades - initially in Asia, but now almost worldwide. Mammals have also been infected. For some years now, a particular group of H5N1 viruses, the so-called clade 2.3.4.4b, has been spreading and has also infected numerous cattle in the USA.

There have been no cattle with H5N1 infection to date. It is still unclear how the transmission from a wild bird to a cow took place. What is certain is that humans have now also been infected by cattle. According to the US health authority CDC, four cases had been recorded by the middle of the year in the context of the outbreak in US dairy farms.

Can humans get infected from cattle?

According to the CDC, four human cases have been recorded so far in the context of the outbreak in US dairy farms. Each time, conjunctivitis was one of the symptoms, explains the Vice President of the Friedrich Loeffler Institute (FLI), Martin Beer. "Humans have the bird flu receptors in their eyes." If a worker touches their eye during milking, for example, the pathogen can dock on.

Pasteurized milk is considered safe, as recently confirmed by a study published in the Journal of Virology. According to the study, non-infectious traces of the viral genome were found in 20 percent of the 300 or so pasteurized milk products examined from 132 US processing plants, and infectious virus was not found in a single case.

However, infection via raw milk is considered possible. Farm cats have often been infected via lapped up raw milk in recent months. In many of the recorded cases, they died, as Beer says. "The virus usually also infects their brains." This finding is not entirely new: there have also been outbreaks of bird flu in cats in Poland and South Korea - always via contaminated food, not from cat to cat.

The situation is different for certain marine mammals and species kept for fur farming, such as mink and Arctic foxes. For marine mammals, transmission between conspecifics is considered highly probable; for animals in fur farms, it is largely certain, as Beer says.

Neurological symptoms, i.e. brain damage, are also to the fore in these animals. The proportion of fatally ill animals is high. "In the very rare cases in humans, there are no such neurological symptoms, but rather the classic respiratory problems associated with influenza."

How dangerous would an infection be for humans?

Thanks to previous infections and vaccinations against other forms of flu, the human immune system would not start from scratch if it came into contact with the virus. This is what previous research suggests, according to an article in Nature magazine.

However, according to the information, this would probably not prevent H5N1 from causing serious damage to global health in the event of a pandemic. According to Nature, infection with seasonal flu viruses only offers limited protection against the new flu strains, which are genetically different from them.

In the event of an H5N1 pandemic, older people could potentially be better protected than younger people, according to the article, because they probably came into contact with similar flu strains during their childhood. This has already been shown in previous waves, such as swine flu.

Is the next pandemic on the way?

Although there are no concrete signs of this, leading experts have expressed concerns. In view of the spread of H5N1 in the USA, Christian Drosten, chief virologist at the Charité hospital in Berlin, for example, has identified the bird flu virus as a possible trigger for a coming pandemic.

The pathogen has recently appeared in dairy herds in the USA and "has even appeared in dairy products on the market there", Drosten told Redaktionsnetzwerk Deutschland. "There has never been anything like this before, such extremely large outbreaks in cows - all the experts are worried."

The spread of bird flu among mammals could also be "mild, the virus needs several steps to adapt, and perhaps it will be under control before then," Drosten continued. "But it could also be the start of the next pandemic, which we are watching live here."

What about vaccines?

In the event of a bird flu pandemic, vaccines for humans could be available quickly, according to Berlin infectiologist Leif Erik Sander. "We have vaccines that have been approved and could be adapted very quickly the moment a virus triggers a pandemic," said the Charité professor in an online press conference. However, production capacities would have to be ramped up for this.

Sander is talking about influenza vaccines that would have to be adapted to the sub-variant of the bird flu pathogen. The avian flu virus H5N1 is an influenza A virus like the seasonal flu pathogens that circulate in humans.

The EU recently secured 665,000 vaccine doses from the manufacturer CSL Seqirus against the transmission of bird flu from animals to humans for several member states.

Are there any new developments?

According to the German Association of Research-Based Pharmaceutical Companies (VFA), a number of companies are currently developing novel flu vaccines based on mRNA - the technology that was also used in part for Covid-19 vaccines.

These include the US company Moderna and the biotech company Curevac in collaboration with the biopharmaceutical company GSK. The second phase of clinical testing of the avian flu vaccine is to start as soon as possible, said Curevac spokesperson Patrick Perez. Further development will be taken over by GSK. Three clinical phases are usually required for approval.

It is a pre-pandemic vaccine, explained Perez. The principle is based on developing a vaccine before a possible outbreak to such an extent that it can be approved and made available quickly in the actual event of a pandemic. "This offers the advantage of being able to react very quickly in the event of a pandemic without having to approve, pre-produce and store a vaccine when it may never be needed."

According to Moderna, the Moderna candidate is also undergoing clinical trials. "We expect the first preliminary results from these studies later this year. If these results are positive, the vaccine candidate will move into Phase 3 development," the company announced.

With material from dpa and afp.

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