Avian and pandemic influenza

The big picture

The difference between human and avian influenza

Influenza is a viral respiratory infection in humans that is more serious than the common cold.  It is commonly called ‘the flu’ and occurs seasonally every year, most often in winter. 

Avian influenza, also known as “bird flu”, is the disease that wild birds and poultry get when they are infected by an avian influenza virus (different from human influenza viruses).  Since 2003, the H5N1 avian influenza virus has been causing severe infection (called highly pathogenic avian influenza) in birds and has spread from Asia to Europe and the Middle East, and now to Africa, affecting over 30 countries.  The H5N1 virus spreads very rapidly through poultry flocks and has a mortality rate among infected birds of 90 to 100 per cent, often within 48 hours.

Fortunately, the H5N1 is still a bird virus. It is easily transmissible among birds but currently does not have the right molecules on its surface to enable it to become a human virus.  However, it has only caused human infections in a small number of those exposed to it, as animal viruses can do without being fully adapted to humans.  The H5N1 virus usually requires intense and close exposure to sick birds or their droppings.  There is no evidence to date of sustained human-to-human transmission, which is the chain reaction spread of ordinary human seasonal flu. WHO provides monthly updates on confirmed human cases.

Fear, lack of information and understanding about avian influenza, have caused some communities to shun those who have been directly affected or even just suspected of having the disease.

A pandemic results when a new human influenza virus emerges.  It spreads more rapidly and widely than seasonal influenza because of the lack of human immunity to the new virus.  Because the H5N1 virus has caused some human infections, it has shown that it has the potential to become a human virus.  If it evolves into a human virus, it is likely to cause a human influenza pandemic.  How the virus will evolve is uncertain: it could happen suddenly; it could take years; or it might never happen.

The impact of a pandemic is hard to predict, but there will be increased illness because humans will have no immunity to the new virus. Mortality rates are likely to be increased and there may be social and economic disruptions. Children will be directly impacted by infections as well as by the potentially devastating social and economic impacts of a pandemic. Everybody needs to prepare for a possible pandemic.