Avian Influenza in Europe: Should We Be Concerned?

Avian Influenza in Europe: Should We Be Concerned?

25.10.2022
Scott Bauer, U.S. Department of Agriculture _Pixnio
Photo: Scott Bauer / Pixnio

[This text has been written by Yvette Moya-Angeler, communications officer at ISGlobal, and Adelaida Sarukhan, scientific writer at ISGlobal]

Avian influenza is an infectious disease that affects birds. It is caused by Type A influenza viruses which belong to the Orthomyxoviridae family.

There are several strains of avian influenza virus. Highly pathogenic avian influenza (HPAI) strains, including some H5 and H7 strains, are highly lethal, especially in domestic birds (geese and ducks seem to be more resistant to disease).

Avian influenza is highly contagious among birds and can spread from farm to farm through the movement of infected animals or contaminated materials (products, vehicles, cages, feed, clothing, etc.). The disease can also spread by contact between migratory and domestic birds.

Why have health authorities been sounding the alarm about avian influenza?

Last winter, Europe experienced an unprecedented wave of avian influenza that stretched from the Svalbard Islands in the Arctic Ocean to southern Portugal and Ukraine, affecting a total of 37 countries. There were 2,467 outbreaks in poultry (leading to the culling of 47.7 million birds) and 3,573 cases detected in wild birds.

Circulation of HPAI viruses is nothing new. However, after a period of epidemiological stability, outbreaks have been on the rise since 2020.

The European Centre for Disease Prevention and Control (ECDC) reports in its most recent overview that the number of infected poultry premises was five times higher from 11 June to 9 September 2022 than during the same period in 2021. During the months in question, 788 HPAI virus detections were reported in 16 European countries: 56 in poultry, 22 in captive birds and 710 in wild birds.

According to the ECDC, several colony-breeding seabird species along the northwest coast of Europe exhibited widespread and massive mortality from the H5N1 virus, the predominant subtype and main cause for concern in Europe in recent years. These are unprecedentedly high levels of virus detection, representing an ongoing risk of infection for domestic birds, especially considering that autumn—migratory bird season—has only just begun.

Avian influenza in Spain

Over the course of 2022, 36 outbreaks of H5N1 avian influenza have been reported in Spanish poultry. The two most recent such outbreaks occurred at laying hen farms in Guadalajara in September.

A worker at one of these farms contracted the disease, becoming the first human case detected in Spain (and the second in Europe). After testing positive for avian influenza, the man stayed in isolation; he was asymptomatic and did not require hospitalisation. He tested negative on 28 September without having infected anyone.*

 

*UPDATE: Influenza A(H5N1) virus was detected in a sample from another worker of the farm on 13 October. He was asymptomatic and remained in isolation until 22 October when a second sample tested negative. Two close contacts of his were identified and tested negative.

 

Photo: Dattatreya Patra / Unsplash

Should we be concerned? Can people catch avian influenza?

The avian influenza virus is highly pathogenic for birds, but the risk to humans is, for now, very low. Humans can become infected only in exceptional cases and by direct contact with infected birds or their droppings, in the absence of hygienic and sanitary measures. Between January 2003 and 29 September 2022, the World Health Organisation (WHO) has recorded 865 cases of human infection with avian influenza A virus (H5N1 subtype), mostly in Asia and in people living in close contact with infected birds. As far as the ECDC is aware between December 2021 and September 2022 37 cases of human infection were reported in China and Cambodia and one case was reported in the United Kingdom. (These data do not include the asymptomatic Spanish case detected in Guadalajara in September.)

The risk to the general population is, at present, nearly non-existent As noted by the Spanish Ministry of Health, “the number of cases in humans remains very small compared to the total number of affected birds. And in Europe, despite the high density of factory farms, which encourage the rapid spread of the virus, animals do not typically live in areas inhabited by humans. Only people who work on farms and in contact with birds, such as veterinarians or staff responsible for disposing of affected animals, need to take precautions. Nevertheless, it is best to avoid contact with wild birds. If any sick or dead birds are found, the regional veterinary authorities should be notified so that they can remove and analyse the affected animals.

What are the symptoms of avian influenza in humans? Is it dangerous?

A person infected by the avian influenza virus can develop anything from a mild upper respiratory tract infection (fever and cough) to severe pneumonia, septic shock, acute respiratory distress syndrome and even death.

Avian influenza is considered very dangerous in humans as it is much more lethal than seasonal influenza or COVID-19. In fact, more than half of the people who have been infected by the H5N1 subtype have died (866 reported infections, 456 deaths).

Can someone infected with avian influenza transmit the virus to another person?

To date, there have been no reported cases of human-to-human transmission. The virus now circulating in birds does not have the capacity to spread easily from human to human. Nevertheless, we must remain vigilant in case the virus acquires this capacity through mutation. This seems unlikely, but it is possible.

 

Photo: Dattatreya Patra / Unsplash

Do I need to take precautions if I eat poultry or eggs?

No. So far there is no scientific evidence of avian influenza spreading via the food chain. People can catch the virus if they inhale droplets sneezed by infected birds or dust from their beds or droppings.

Why does the virus spread so quickly from one country to the next?

Bird migration routes are thought to play a role in the geographical spread of the virus. Some studies have suggested that members of the Anatidae family (ducks, geese and swans), especially migratory ones, are natural hosts for the virus. Climate change may also play a role: if migration routes change, wild birds carrying the virus may be able to reach new territories.

The disease can also spread from one country to another through the the international smuggling of live birds.

What can we do?

We must continue to work from a One Health perspective, with the understanding that human, animal and planetary health go hand in hand. Three quarters of today’s emerging diseases are zoonotic, meaning that the pathogen jumps from an animal to a human being. Globalisation, aggression against ecosystems, invasion of natural habitats and factory farming make it ever more likely that we will continue to see outbreaks of emerging viruses.