There has been an outbreak of H5N1 bird flu in Ouagadougou, Burkina Faso’s capital. The viral disease, also called avian influenza, killed 441 chickens out of a flock of 641 on a farm.
There have been several outbreaks bird flu across Africa over the past 18 years. Nigeria was the first African country to report an outbreak in February 2006.
Daniel Oluwayelu, a virologist and bird flu expert, tells us more about the disease.
What is bird flu?
Avian influenza, or bird flu, is a highly contagious viral disease of birds caused by the influenza A viruses. It was previously known as “fowl plague” and was recognised as an infectious disease of poultry in Italy as far back as 1878.
Although avian influenza A viruses occur naturally among wild aquatic birds worldwide, they are also known to infect other animals, including ducks, chickens, turkeys, pigs, whales, horses, seals, dogs and cats.
Exposure to animal influenza viruses can lead to infection and disease in humans – ranging from mild, flu-like symptoms or eye inflammation to severe, acute respiratory disease or death.
Domestic poultry may be infected with two types of bird flu viruses: highly pathogenic avian influenza (HPAI) A viruses or low pathogenic avian influenza (LPAI) A viruses. All outbreaks of the highly pathogenic form have been caused by influenza A viruses of the sub-types H5 and H7.
The highly pathogenic viruses spread quickly and may kill nearly an entire poultry flock within 48 hours. The low pathogenic viruses may not cause symptoms or may cause only mild symptoms such as ruffled feathers or a drop in egg production.
How does it spread?
Influenza A viruses circulate in their natural hosts: wild aquatic birds. Infected birds shed the bird flu virus in their saliva, mucus and faeces. Transmission or spread of the virus occurs primarily by the oral-faecal pathways through direct contact with secretions from infected birds, especially through faeces or indirectly through contaminated feed and surface water.
Most bird flu viruses, including sub-types H5 and H7, are of low pathogenicity and cause sub-clinical infections of the intestinal or respiratory tract. This means they do not easily cause disease and have only mild symptoms. The virus is spread mainly through faeces and droplets released during coughing and sneezing.
