Pandemic alert levels: what do they mean?

In the threat of a health pandemic, the World Health Orgaisation has a series of levels to alert the public to what is currently happening and how serious a worldwide health threat could become.

The current swine flu outbreak, which started in Mexico, has the threat of becoming a global pandemic. 

A pandemic means an epidemic of an infectious disease, that spreads throughout a large number of people and can spread worldwide.

A pandemic begins when:

• there has been the introduction of a new disease into a population
• it infects humans and causes serious illness, including death
• the disease can speard easily rapidly from human to human contact

The World Health Organisation uses a six stage phase for alerting the general public to an outbreak (the swine flu outbreak is currently on level 5)

Phase 1 - viruses that may be circulating among animals have no impact on humans.

Phase 2 - an influenza virus in animals is known to cause infection in humans, and could become a pandemic threat.

Phase 3 - the animal or human influenza virus causes some small outbreaks among close populations but not through human to human contact. There may be some human to human contact among two people who work closely together, but the virus is not transmitted through general contact.

Phase 4 - Human to human transmission of a virus is confirmed and causes community level outbreaks. Any country that has any of these outbreaks must consult with the WHO immediately to discover what is the best course of action to deal with the virus outbreak. This stage does not mean a pandemic is imminent, but it is a possibility.

Phase 5 - The virus is spread by human to human contact and has now spread across two countries or more in one of the WHO regions (continents). When a stage 5 is declared, it means that a pandemic is most likely to happen and that countries should start preparing for such an event.

Phase 6 - a worldwide pandemic. There has been a community outbreak in a country in another WHO region, and a global pandemic is underway.

Previous Global Pandemics:

1918 - a global outbreak of Spanish Flu (originated in birds).

It was thought to have first hit soldiers in Europe during World War I, as their immune systems were weakened by war.

It spread to China, killing a million people there, and after it spread to North America, it killed about 40,000 people in about two weeks arond mid-October. In total, it is recorded that 50,000 people died in Canada.

The mortality rate was highest between 20 to 50 year olds, and there was never any vaccine developed as there wasn't enough time. However, after about 18 months, the virus seemed to just disappear. The final death toll was written as 40 million people worldwide.

1957 - Asian Flu

This flu started in birds in Asia, and the infection first spread across Asia, India, Africa, and the Middle East. In September of that year, cases started turning up in North America, and schools and public places started closing in an effort to contain the virus.

In December the virus started to subside, but reappeared in January, and by the spring of 1958 70,000 people had died in the United States. However in India and Asia, over two million people died from this outbreak.

1968 - The Hong Kong Flu

This flu was first found in the early months of 1968 in Hong Kong, but by September it had reached North America, and was declared a global pandemic by December.

Experts thought that the spread was not as great as it hit at a time when children were out of school and were therefore not able to spread it as much.

This is the mildest pandemic compared to the other two, but it was still declared a pandemic and it still claimed about a million lives worldwide. It did make a mild reappearance in 1970 and 1972.

For some more information on pandemic flu.