There is a global state of alert to bird flu epidemic that has killed millions of domestic and wild birds in the last 3 years, mainly in South East Asia and Eastern Europe. The same H5N1 strain of bird flu has affected humans, with 169 confirmed cases and 92 deaths as per 8th March, 2006, in Asia and Europe. However no case of bird flu by March 08,2006 has been so far reported in human beings in Africa. The disease in birds recently reached Africa, with cases reported in Nigeria, Egypt, Niger and Cameroon.

What is 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. Seasonal influenza causes illness in approximately 5% of adults and 20% of children each year (Note: different surveys report different numbers, and it varies form year to year). Seasonal influenza results in approximately 250,000 to 500,000 deaths globally each year, mostly in the elderly and the very young.

Avian influenza, also known as “bird flu”, is the disease that is caused by Avian Influenza virus (different from human influenza viruses) and it affects wild birds and poultry. 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 percent, often within 48 hours.

The H5N1 is still a bird virus and 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 caused a few human infections, as animal viruses can do without being fully adapted to humans. The H5N1 virus has only caused human infections in a tiny fraction of those exposed to it, and usually requires intense and close exposure to sick birds or their droppings. Children appear to be at an increased risk of H5N1 infections and fatality. There is no evidence to date of sustained human-to-human transmission of avian influenza virus as occurs in the spread of ordinary human seasonal flu.

What is an influenza pandemic?
A pandemic is a widespread usually global outbreak of any disease among humans. Pandemic influenza, different from seasonal and avian influenza, is a rare but recurrent event that has occurred every 11 – 42 years in the past few hundred years. Pandemic influenza affects all populations regardless of national boundaries or socio-economic status. Over the past 100 years there have been three pandemics: 1918 (approximately 50 million deaths), 1957 (approximately two million deaths), and 1968 (approximately one million deaths). Because pandemics bring on an abrupt surge in illness and death, they can cause severe disruption and economic losses.

When does an influenza pandemic occur?
A pandemic results when a new human influenza virus emerges and starts spreading as easily as the regular seasonal influenza. The 1918 influenza pandemic was originally an avian influenza virus that underwent a series of mutations that enabled it to become a human virus. The H5N1 virus has undergone some of the same mutations as the 1918 virus. The 1957 and 1968 influenza pandemics emerged from mixing of avian with human influenza viruses rather than by mutation.

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 (i.e., one that passes easily from person to person), it is likely to cause a human influenza pandemic. Birds will no longer be a concern; people will spread the virus among themselves. How the virus will evolve is uncertain: it could happen suddenly; it could take years; or it might never happen.