Avian influenza

It’s important to remember that this virus mostly affects wild and domestic birds. It rarely affects humans and there’s no evidence from the current outbreak that this virus has acquired the ability to spread from person to person.

H5N1 is made up of different subtypes, called clades, and despite the high number of clade 2.3.4.4B outbreaks (the predominant strain of H5N1), we’ve seen relatively few reports of this virus in mammalian and human populations, which is reassuring. 

Since the beginning of 2021, 30 people have been diagnosed with H5N1 and reported to WHO (including those who were recently exposed to dairy cattle in the United States), and all H5N1 cases reported in Europe and North America have been asymptomatic or mild. For example, the first person infected in the United States reported conjunctivitis as their only symptom.

All the H5N1 infections in humans so far have been sporadic, occurring through direct contact with infected birds or mammals or in environments such as live poultry markets or other premises with infected animals. Among these cases, no human-to-human transmission has been reported.

Over the past 2 decades, the H5N1 viruses have remained well adapted to birds rather than to mammals such as humans. To infect and potentially transmit in mammals, including humans, the virus would need to evolve or adapt to possess particular mutations or gene segments. Rapid characterization and sequencing of these viruses and data sharing are critical to assess whether they have developed adaptation mutations. 

These viruses are always evolving and spreading, and so it’s essential that continuous, real-time monitoring takes place. Unfortunately, H5N1 is already circulating in the wild bird population, which has the potential to infect farmed animals across the Region. To tackle this threat and prevent the current situation from worsening, countries in the Region need to enhance their prevention, preparedness and response efforts.

WHO/Europe provides guidance and tools on conducting disease surveillance, identifying potential risks for human health, bolstering understanding about how the disease is transmitted from other mammals to people, ascertaining if human-to-human transmission has occurred, and determining the public health measures needed to reduce ongoing risk of human infection.

Pathogens such as influenza have the potential to spread quickly with major global consequences. Like other respiratory viruses, H5N1 could be a potential threat. Nevertheless, this strain has been circulating for a long time compared to COVID-19, for example, which was a totally new virus.

This means that WHO and partners have already made preparations to try to prevent this from happening. This includes the summary and publication of genomic characteristics of currently circulating zoonotic influenza A viruses for pandemic preparedness twice a year, which allows manufacturers to create what’s called CVVs – candidate vaccine viruses – that are used to produce vaccinations and can be administered when necessary.

Surveillance is also vitally important. Countries report to a global surveillance network called the Global Influenza Surveillance and Response System (GISRS), which monitors the spread, mutations and characteristics of H5 (avian influenza) and its respective strains.

Vaccines against avian influenza A (H5N1) for humans have been developed for pandemic use but are not widely available. Through GISRS, WHO monitors the evolution of the virus, conducts risk assessments and recommends the development of additional new CVVs for pandemic preparedness purposes. This means that vaccine production can start immediately with the available CVVs if there is a need.   

Seasonal influenza vaccination does not protect against H5N1 infection. WHO recommends routine seasonal influenza vaccines for those who are potentially exposed to avian influenza to reduce their risk of getting sick with both human/seasonal and avian influenza viruses at the same time.

WHO/Europe works closely with other organizations that manage the animal health aspect of zoonotic diseases, including the World Organisation for Animal Health, the United Nations Food and Agriculture Organization, and the European Food Safety Authority. We compile and recommend public health actions, alongside rapid sharing of information and virus sequence data.

We also recommend that laboratories and clinicians be on alert for potential zoonotic infection in patients who had exposure to avian influenza, and that efforts be made to reduce human exposure to birds and mammals potentially infected with avian influenza viruses. 

This requires in-country strengthening of farming biosafety and biosecurity measures around known animal reservoirs to limit the risk of spillover events in mammals, including humans. Infection prevention and control measures for animal workers, farm visitors, and those who may be involved in animal husbandry or culling are key.  

Importantly, WHO also offers health information and advice targeted to different population groups to increase their knowledge of the virus and the protective measures to adopt based on their risk.

The following recommendations apply to everyone, especially if you’re in an area where the virus is circulating: 

• Refrain from touching sick, potentially sick, or dead birds or animals and promptly notify the relevant authorities about them.
  


• Choose pasteurized milk instead of raw milk. If pasteurized milk is unavailable, boil raw milk before consuming it.
  


• Follow basic food hygiene practices, including thorough cooking of eggs, poultry, meats and other animal products and the use of separate utensils for handling raw and cooked food.

If you’re a health worker near dairy or poultry farms in areas infected by avian influenza, be vigilant for patients with exposure to birds or animals who show symptoms of influenza-like or acute respiratory infections.

If you suspect avian influenza, refer the patient for testing and notify the relevant authorities promptly. Remember to follow infection control protocols when attending to patients.

Where possible, health authorities should consider testing all asymptomatic individuals who have had significant contact with infected poultry/mammals or potentially infected environments without PPE. Those who develop respiratory symptoms should be rapidly sampled and precautionary infection control measures should be put in place to prevent further spread among humans.

WHO also recommends routine seasonal influenza vaccines for those who are potentially exposed to avian influenza, to reduce their risk of getting sick with both human/seasonal and avian influenza viruses at the same time.