Influenza, commonly called ‘the flu’, is caused by one of the family of influenza viruses. There are many types of animal and human flu viruses. Ordinary human flu affects millions of people each year. This influenza is a contagious infection of the respiratory tract, which affects people of all ages. In many cases, flu is short-lived and can resolve on its own. However, in the very young, the elderly, and people with chronic diseases, influenza can cause severe illness and life-threatening complications. Influenza kills 250,000 to 500,000 people worldwide each year.

Avian (bird) flu

Avian influenza, or “bird flu,” is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs. Avian influenza viruses are highly species-specific, but have, on rare occasions, crossed the species barrier to infect humans. This occurred in 2006 and again in 2009 with the ‘swine flu’ pandemic.

What is a flu pandemic?

A flu pandemic occurs with the appearance of a new influenza virus subtype against which the global population has no immunity. This may result in several, simultaneous epidemics worldwide with high morbidity and mortality. The increase in global transport and communications, as well as urbanisation and high population density, further increase the risk of rapid global spread of a pandemic. Such pandemics occurred in 1918, 1957, 1968, and 2009.

Pandemic flu vaccines

When there is a risk of a flu pandemic occurring, we work closely with the World Health Organization to develop a vaccine. Find out more about our pandemic flu vaccine development process (PDF).