Avian Flu

Amid fears of avian flu spreading, mass bird deaths have been reported from Muttar and Ambalappuzha North in Alappuzha district.

What is bird flu?

Avian influenza or Bird Flu refers to the disease caused by infection with avian (bird) influenza (flu) Type A viruses.
These viruses occur naturally among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species.
It is a zoonotic disease that affects wild and domestic bird populations.
Avian flu viruses do not normally infect humans.

Spread:

The disease makes its presence felt particularly during winter in most of India and other parts of the globe.
This is because, as wintering, migratory birds arrive and bring pathogens with them.
Temperature is also a factor: the virus thrives better in cooler climes, thus enabling its spread during winter.

Types of Influenza Virus:

There are four types of influenza viruses: influenza A, B, C, and D

Influenza A and B are the two types of influenza that cause epidemic seasonal infections nearly every year.
Influenza C mainly occurs in humans but has been known to also occur in dogs and pigs.
Influenza D is found mainly in cattle. It’s not known to infect or cause illness in humans yet.

Avian influenza Type A viruses:

Type A viruses are classified based on two proteins on their surfaces – Hemagglutinin (HA) and Neuraminidase (NA). There are about 18 HA subtypes and 11 NA subtypes.
Several combinations of these two proteins are possible e.g., H5N1, H7N2, H9N6, H17N10, H18N11, etc.
All known subtypes of influenza A viruses can infect birds, except subtypes H17N10 and H18N11, which have only been found in bats.