Bird Flu Overview

What is bird flu?

Bird flu, also known as avian influenza, refers to influenza A viruses that usually affect birds. Some strains can cause large outbreaks in poultry (farmed birds), causing flocks to die suddenly. As migratory wild birds can carry the virus without becoming ill, they can spread avian influenza from area to area and even continent to continent. 

The many strains of avian influenza viruses can generally be classified into two categories according to the severity of the disease in poultry:

• low pathogenicity avian influenza (LPAI) that typically causes little or no clinical signs; 
• high pathogenicity avian influenza (HPAI) that can cause severe clinical signs and possible high mortality rates.

Human infections

Some bird flu viruses infect humans, causing a severe or fatal infection. The H5N1 and H7N9 strains have infected hundreds of people, while some other bird flu viruses (including H5N6 and H10N8) have only occasionally infected humans. 

People get bird flu from direct contact with infected birds or their environment, although in some cases there was no such exposure (and it is unknown how these people were infected). Usually, only one human is infected at a time ("sporadic"), however, there have been "clusters" of cases where several people were infected. These clusters may have been due to people being exposed to birds at the same time and place. In some instances there has been limited human-to-human spread.

What is the risk to individual humans? Is there a risk of a pandemic?

Wherever bird flu occurs, there is a potential risk to humans, hence it is important to monitor the global situation. Any of the following scenarios could occur with any strain of bird flu. It could:

• Continue as it is, causing bird outbreaks and sporadic or small clusters of human infections
• Spread geographically - with bird and human cases occurring in new areas
• Slow or stop – if the source of the virus is identified and controlled 
• Mutate to become more transmissible from person to person – which could cause a global influenza pandemic.