Pandemic

A pandemic (from Greek παν pan all + δήμος demos people) is an epidemic (an outbreak of an infectious disease) that spreads across a large region (for example a continent), or even worldwide.

According to the World Health Organization, a pandemic can start when three conditions have been met:

• the emergence of a disease new to the population.
• the agent infects humans, causing serious illness.
• the agent spreads easily and sustainably among humans.

A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For example cancer is responsible for many deaths but is not considered a pandemic because the disease is not infectious (although certain causes of some types of cancer might be).

The World Health Organization (WHO) has developed a plan to prepare globally the fight against influenza. It defines the stages of a pandemic and makes recommendations for national measures before and during a pandemic. The phases are:

Interpandemic period:

• Phase 1: No new influenza virus subtypes have been detected in humans.
• Phase 2: No new influenza virus subtypes have been detected in humans, but an animal variant threatens human disease.

Pandemic alert period:

• Phase 3: Human infection(s) with a new subtype but no human-to-human spread.
• Phase 4: Small cluster(s) with limited localized human-to-human transmission
• Phase 5: Larger cluster(s) but human-to-human spread still localized.

Pandemic period:

• Phase 6: Pandemic: increased and sustained transmission in general population.

• Epidemic
• List of epidemics

• Steward's "The Next Global Threat: Pandemic Influenza".

• WHO - Authoritative source of information about global health issues
• Past pandemics that ravaged Europe
• CDC: Influenza Pandemic Phases
• U.S. government's pandemic flu and avian flu information site