Bird flu: how much of a risk is there for humans?

Cinzia Rizzi
Sun, 18 June 2023 


In recent months, bird flu has again come to the fore of the news agenda. H5N1, a virus belonging to the influenza A subgroup, has caused the deaths of millions of birds and also, on a much smaller scale, contagion among mammals, including some humans. Certain regions of the world, such as North America and South-East Asia, have been most affected, while in Europe the risk is currently low.

"It is quite a serious situation for the bird population," says World Health Organization epidemiologist Richard Peabody. "However, the risk to the human population is low. This is an important message we want to convey. The risk of it passing from birds to humans is quite low for the general population and we have no evidence that the avian influenza virus has the ability to spread from person to person."

Preventive measures for poultry workers

Human infections usually involve people who have been in close contact with infected birds, usually poultry. Therefore some preventive measures are still essential.

"We are a bit more concerned about poultry workers," says Peabody. "They are more at risk of being exposed to the virus. So we have some recommendations both for them and for the general public. And for the general public, it is simply to be sensible and not to touch dead or dying birds. But more importantly, for people working in the poultry industry, there are recommendations on what workers should do in terms of protection, wearing protective equipment and monitoring their health."

Vaccination against seasonal flu could have a positive impact: it would reduce the risk, for those in close contact with poultry, of so-called viral recombination, where the seasonal flu virus combines with the avian flu virus.

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France has outlined a prevention campaign to vaccinate poultry. Two vaccines tested have already proven to be highly effective for ducks raised to make foie gras. This should start in October. Farmers are pleading for vaccinations to start in the summer, but the ministry said that time was needed to ensure safe testing, production and storage of vaccines.

The concern of poultry farmers doubtless arises from recent history: during the previous epizootic in 2022-2023 in France, six million birds were slaughtered. In 2021-2022, the figure stood at 22 million.

In May 2023, the virus was reported to the Gers, Landes, and Pyrenées-Atlantiques departments, in the southwest of France.

A total of 85 farms were infected. Now, says Marc Fenot, the French Agriculture Minister, the peak incidence has passed. The risk of spreading the virus on the French mainland was reduced to "moderate" from "high".

What you need to know about bird flu

Avian influenza is an acute infectious disease of domestic and wild birds that was discovered over 140 years ago.

The disease is characterized by damage to the digestive and respiratory organs in birds and has a high mortality rate.

Avian influenza can be transmitted from animals to humans in two main ways: directly from birds or a contaminated environment, or through an intermediate host, such as a pig.

People who are in close contact with infected birds and animals, such as farm workers, are particularly susceptible to the virus.

Laboratory tests are needed to diagnose human infection with avian influenza.
Bird flu symptoms in humans

Human infection with the avian influenza virus can cause diseases ranging from a mild upper respiratory tract infection to a more severe, potentially fatal illness. There is also evidence of cases of conjunctivitis, manifestations of gastrointestinal symptoms, encephalitis and encephalopathy (decrease in blood flow or oxygen to the brain).

So far, there is no evidence suggesting bird flu could mutate into a form that can be transmitted from person to person.

Should Europeans worry?

In March and April, the incidence of avian influenza among poultry decreased compared to the previous reporting period (December to February).

However, black-headed gulls are still heavily affected by the virus.

The virus continues to spread to the Americas and is expected to even reach Antarctica in the near future. Two cases of avian influenza virus have also been reported in cats in the US and one in a dog in Canada.

The risk to the general population in Europe remains low and increases to low to moderate for workers and others who come into contact with potentially infected sick or dead birds and mammals.

These are the main findings of the latest avian influenza report compiled by the European Agency Food Safety Authority (EFSA), the ECDC and the European Union Reference Laboratory (EURL).

In March 2023, the European Food Safety Authority (EFSA) launched the Bird Flu Radar project. This is an early warning system for outbreaks of avian influenza.

WHO recommendations

The nature of influenza viruses is constantly changing. Given the large-scale circulation of the virus in birds, the WHO stresses the importance of maintaining global surveillance of its progress.

It recommends that all people who work with poultry or wild birds be vaccinated against seasonal influenza to reduce the theoretical risk of mixing with other viruses.

Travellers to countries with reported outbreaks of zoonotic influenza should refrain from visits to farms and avoid contact with animals in markets where live animals are sold. They should not go to places where animals are slaughtered and should avoid touching surfaces that are visibly contaminated with animal faeces.

General precautions include regular handwashing, good hygiene and ensuring food safety.