WHO PANDEMIC ALERT PHASES

Phase 1: No infections in humans are being caused by viruses circulating in animals.












Phase 2: Animal flu virus causes infection in humans, and is a potential pandemic threat.












Phase 3: Flu causes sporadic cases in people, but no significant human-to-human transmission.












Phase 4: Human-to-human transmission and community-level outbreaks.












Phase 5: Human-to-human transmission in at least two countries. Strong signal pandemic
imminent.











Phase 6: Virus spreads to another country in a different region. Global pandemic under way.












Post-peak: Pandemic activity appears to be decreasing though second wave possible.
Post-pandemic: activity returns to normal, seasonal flu levels.

Source: Swine Influenza Top News

Flu Pandemics

1918: The Spanish flu pandemic remains the most devastating outbreak of modern times. Caused by a form of the H1N1 strain of flu, it is estimated that up to 40% of the world's population were infected, and more than 50 million people died, with young adults particularly badly affected

1957: Asian flu killed two million people. Caused by a human form of the virus, H2N2, combining with a mutated strain found in wild ducks. The impact of the pandemic was minimised by rapid action by health authorities, who identified the virus, and made vaccine available speedily. The elderly were particularly vulnerable

1968: An outbreak first detected in Hong Kong, and caused by a strain known as H3N2, killed up to one million people globally, with those over 65 most likely to die

Source: Swine Influenza Top News