Public Health and Avian Influenza

Avian influenza viruses normally only infect birds and pigs. In cases where avian influenza viruses have directly infected people, human-to-human transmission has not taken place. Genetic re-assortment may result in new viruses that can be transmitted between humans. This could result in a human influenza pandemic. A pandemic is a global outbreak of disease. In the 20th century this has been documented 3 times.

1918 (H1N1) - "Spanish Flu". Caused the highest number of known flu deaths. 20-50 million people may have died worldwide.
1957 (H2N2) - "Asian Flu"
1968 (H3N2) - "Hong Kong Flu"

Cases of Avian Influenza in humans

For more information on avian influenza in humans see:

Ilaria Capua, Dennis J Alexander
Avian Influenza and human health
Acta Tropica 83 (2002) 1-6
Abstract

Human Influenza Infections
There are also influenza viruses that are specifically adapted to humans. Read more about Influenza in Humans.

The possibility for genetic re-assortment exists in concurrent infections with human and avian influenza strains. Read more in geneticre-assortment.