Pandemic influenza occurs when a strain of the flu virus becomes highly contagious, spreading easily and quickly around the world. Because the population is not immune to a new virus, it will affect more people causing higher rates of illness and death.

Pandemics are unpredictable and it is hard to know when one will occur, what type of flu, and how severe it will be. However, most experts believe we are overdue for such an event. This pandemic could occur at any time; it is not just a winter illness.

How the virus spreads

Human influenza mostly travels from one person to another as a virus generated when an infected person coughs or sneezes. Viruses can live on hard surfaces for 24–48 hours (within a particle of fluid), on cloths and tissues for 8–12 hours, and on hands for 5–20 minutes. The virus can also be transmitted if someone touches a surface and then touches their eye, nose, or mouth.

Influenza has a one to four day incubation period and, once infected an individual remains infectious from the day before symptoms of the illness appear and throughout the three to five days of the illness.

People are most infectious during the first three days of illness.

Protecting yourself from flu

Immunisation with vaccines is a means of flu prevention. The usual yearly flu jabs will not protect you against a new pandemic, but they will help stop you getting ill from other influenza viruses. These viruses change all the time, so you need to get vaccinated every year.

Types of flu

Influenza is a very infectious illness caused by a virus. It is much more serious than a common cold and can leave you ill for up to 10 days. Most people refer to a cold as the flu, but influenza is a specific illness with a fever, headaches and fatigue. There are many types of influenza strains infecting humans and animals.

Avian influenza (bird flu)

Birds can be infected by flu and this is called avian influenza. Very rarely an avian influenza virus can also infect people – this happens when people have close contact with infected birds. 

Swine influenza

This is a new influenza virus which originally spread from pigs to humans. A strain of the virus was detected in April 2009 with cases recorded worldwide.