Where does the bird flu come from?

Bird flu in animals

Avian influenza is caused by influenza virus A, subtypes H5 or H7. A distinction is made between a highly pathogenic and a low pathogenic avian influenza. Mutations can result in highly pathogenic avian influenza viruses (low pathogenic avian influenza, LPAI) (highly pathogenic avian influenza, HPAI). HPAI make animals and humans sick, it is a zoonosis. Pigs can also be infected with avian influenza viruses.

All bird species are affected, especially chickens and turkeys. Infections with HPAI usually lead to clear signs of disease in farm poultry. Waterfowl, such as ducks and geese, seldom get sick and if so, then less seriously. But you can spread the pathogen further. LPAIs, on the other hand, usually only trigger mild and less specific symptoms.

Animal disease

Poultry infected with highly pathogenic avian influenza have difficulty breathing. In the case of chickens there is a decline in laying performance and many animals die. The eggshells become thin or missing entirely. Swelling in the head area can be observed. The animals seem lethargic. There are usually no symptoms to be seen in water birds.

Exclusion investigation

In the case of unclear herd problems with AI-like symptoms, but without urgent suspicion, a sample can be taken by veterinarians or the pathology department after consultation with the National Reference Center for Poultry Diseases (NRGK) in order to rule out an AI infection. No epidemic police measures in accordance with Art. 84 of the Animal Diseases Ordinance need to be taken.

Contagion and spread

The infection by the influenza virus A occurs via the respiratory tract by inhaling contaminated droplets of exhaled nasal, throat or eye secretions. Inhaling dust containing pathogens that has been in contact with virus-containing faeces can also lead to infection. Young animals are most susceptible to avian influenza.

Avian influenza is spread all over the world. It occurs periodically in Europe. No HPAI has been detected in farm poultry in Switzerland since 1930. Since LPAI is usually symptom-free and can mutate into HPAI, LPAI has been actively monitored in Switzerland since 2006. For results, see the Animal Health and Zoonoses Surveillance Report under “Further Information”.

What to do?

  • In poultry farms, the hygienic measures (e.g. hygiene sluices) must be strictly observed.

To prevent the disease from being introduced, the FSVO has issued emergency ordinances prohibiting the import of poultry and poultry meat products from countries in which the highly pathogenic avian influenza is rampant. The federal government can also impose temporary restrictions on the free-range rearing of poultry.

Avian influenza is a highly contagious disease and therefore notifiable. If HPAI is suspected or occurs, strict control measures must be taken. The poultry in contaminated flocks are killed and protection and surveillance zones are set up. Important information for animal keepers in the event of an increased risk of an epidemic or in the event of an epidemic is stored under "Further information> In the event of an epidemic").

Registration of poultry holdings has been compulsory since January 1st, 2010. This also applies to hobby attitudes.

The disease in humans

People who live in close contact with sick poultry, as is the case for example in many areas of Asia or in North Africa, can also develop avian influenza viruses. The first symptoms usually appear two to 14 days after infection and are noticeable in severe flu-like symptoms. More on this on the FOPH website.