The H5N1 virus is currently worrying researchers: unlike usual, it circulates all year round and seems to spread to other bird species without any problems. This is a catastrophe for many wild bird populations – and could also be dangerous for humans.
A highly contagious and deadly strain of bird flu virus H5N1 currently infects millions of wild and ornamental birds, but also poultry in Europe, Asia, Africa and North America. Scientists are particularly concerned about the rapid spread in wild birds. The outbreaks pose a significant risk to already endangered species, are difficult to contain and increase the risk of the virus spreading to humans.
Current situation
Since last fall, H5N1 has caused nearly 3,000 outbreaks in poultry in dozens of countries guided. More than 77 million birds had to be culled to contain the spread in livestock farms. Over 37 million chickens have been culled in the US alone in hopes of slowing the spread of the virus. An estimated 400,000 wild birds have also died in a further 2,600 outbreaks – twice as many as in the last big waves in 2016/17 and 2021. A real mass extinction began in many colonies worldwide one. Researchers say the virus appears to be spreading more easily than ever in wild birds, making outbreaks particularly difficult to contain.
In contrast to previous waves, the outbreaks in Europe in the last two years have also continued into the summer. According to experts, this indicates that avian influenza, also known as bird flu or avian influenza, could now be endemic in European wild bird populations. “It is extremely worrying that the active H5N1 strain is year-round in many species and appears to be able to switch rapidly from one species to another,” explained Willem Van den Bossche from the large international bird protection organization BirdLife. “This change suggests that infection is shifting from migratory birds to wild birds resident or summer resident in Europe and the US, including those breeding in colonies.”
Situation in Germany and humane cases
Since April 2022, the outbreaks of avian influenza in Germany have been declining again. Nonetheless it came outbreaks in Schleswig-Holstein and Lower Saxony since May 2022. Free-range goose farms in particular, but also laying hen farms and very small farms were affected. The last outbreak was registered on August 23, 2022 in a turkey farm in Lower Saxony. Since June 2022, more than 200 wild birds in Germany have also been tested positive for HPAI viruses (highly pathogenic avian influenza A viruses). Hamburg, Mecklenburg-Western Pomerania, Lower Saxony and Schleswig-Holstein were affected. The virus was primarily detected in terns, gannets and seagulls, birds of prey as well as ducks and geese were also affected.
Poultry farmers, especially those with free-range and open-stall systems, are required to protect their poultry stocks from being infected with the virus. Contact with wild birds or their excrements must be avoided at all costs. Increasing poultry losses or significant changes in laying performance or weight gain should be clarified by a veterinarian as soon as possible. It should always be checked for influenza A viruses of subtypes H5 and H7 to be examined.
| Gyn Camp From the 12.09. bis 16.09.22 contributions and campaigns on the subject of “gynaecology” fuel your knowledge. Be there! To the program |
Although humans can also be infected with the virus, human infections have so far been rather rare. By August 18, 2022, 864 human infections with H5N1 from 18 countries had been reported worldwide reported. Of these cases, 456 were fatal. The last case of infection was reported from the USA in April 2022. Scientists are concerned because the high levels of virus circulating in bird populations present more opportunities for transmission to humans.
When the virus mutates
Avian influenza viruses change slowly over time, but the key mutation could make them transmissible to humans and other species so Ian Barr, Associate Director of the WHO Collaborating Influenza Center at the Doherty Institute in Melbourne, Australia. “These viruses are like ticking time bombs,” he explains. “Occasional infections are not a problem – the real crux of the matter is the gradual proliferation of new properties.”
There are two on the viral envelope of the influenza A virus Glycoprotein, hemagglutinin (H) and neuraminidase (N), of which there are 18 and 11 different subtypes, respectively. They appear in different combinations and define the virus and its properties. In the mid-2000s, the H5N1 virus was already quite common in birds. After 2008, it then circulated on a small scale in some countries where it became endemic. In 2014, there was an evolution of the hemagglutinin gene, a new lineage appeared – 2.3.4.4. This change allowed the virus to infect wild birds without inevitably dying them, resulting in massive global spread.
H5N1 is making a comeback
The N protein also changed, H5N8 prevailed over H5N1 and became the world’s dominant strain. Other variants, H5N6 and H5N2 appeared again and again, they were often summarized under the name H5Nx. Now, in the middle of last year, H5N1 resurfaced – and reports of infections in poultry and wild birds skyrocketed. According to Ian Barr, the current virus differs from its predecessor from 2000 in that the number of infected birds, especially among the various wild bird species, is significantly higher this time. The influenza virus expert speculates that the current virus could replicate more or perhaps infect other tissues.
 |
follow the channel pin for further infectiology topics. consequences Are you also interested in news about Corona? Discover here the appropriate channel Corona at a glance. |
In the past, there have been individual cases of human infection, mainly in China among workers who have had increased contact with poultry – so far there has been no transmission from person to person. The virus is still particularly well adapted to the bird, Barr said, but the recent increase in human H5N6 cases in China is of concern. In 2021, 33 cases and 11 fatalities were reported there, and by March 2022 another 17 cases with at least five fatalities were added. While these recent increases in numbers could be due to the increased surveillance of respiratory illnesses and pneumonia during the Covid pandemic, the situation needs to be closely monitored, Barr said.
What can we do?
Between 2013 and 2017, there was a strain called H7N9 that was circulating in China, which worried experts at the time because it led to hundreds of human infections. Today, this virus no longer causes human cases and is also less frequently reported in poultry. This is thanks to a very effective poultry vaccination campaign across China using a combined H5 and H7 influenza vaccine. So far, the vaccine has been viewed critically in Europe and the United States. Faced with the desperation of poultry farmers who have had entire flocks culled, France, the Netherlands and other hard-hit countries are now researching vaccines resumed. Dutch scientists have already begun trials of chicken vaccines, and researchers in France have begun immunizing ducks with a newly developed vaccine. In October, the parties involved want to discuss with the World Organization for Animal Health (OIE) how international obstacles to the transport of vaccinated poultry can be removed.
So far, many countries have refused shipments of vaccinated poultry because they cannot be sure that vaccinating countries really have the virus under control. Experts also fear that vaccination will not completely stop the spread, potentially increasing the long-term risk of human transmission. In addition, the development and widespread application of the vaccines would be very expensive.
The US has not approved the use of avian flu vaccines because of the impact on trade and is relying on large-scale culls to stem the current outbreak.
However, some researchers fear that unless vaccinated carefully, the H5N1 virus could persist and mix with strains of wild birds. Then there is a risk that it will also spread among people. The risk for the European Union and the United States is small, but probably the highest since H5N1 emerged 25 years ago, says US virologist Richard Webby in Science.
Do vaccinations work?
Vaccines already exist: The vaccine Volvac Best is manufactured by Boehringer Ingelheim and is already being used in non-European countries such as Mexico and Egypt to immunize chickens against Newcastle-Disease and H5N1 used. The other and first mRNA vaccine currently being tested in poultry was developed by Ceva specifically for ducks. The results could be available by the end of the year – but that would not be enough. After farmers have vaccinated their herds, they would also need to ensure that the virus does not circulate unnoticed in animals that have not been vaccinated or have not fully responded to the vaccine. Regular swabs would have to be tested for the virus. Actions like these can reduce the risk of transmission to humans or wildlife.
Because there is currently no other protection for people. “Traditionally, avian flu vaccines have not elicited really good and strong immune responses in humans,” says influenza expert Ian Barr. “We have not yet tried mRNA vaccines with these viruses; we know they work to some extent, but how well they work and what protection they would provide is an open question.”
Image source: Wasis Riyan, unsplash