Swine flu: From nowhere to pandemic Phase 5 in less than a month
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TORONTO — Scientists have been anxiously watching H5N1 avian flu for more than a decade, fearing the virulent virus will take hold in humans and cause a pandemic.
But out of nowhere, a new virus has emerged and rocketed the world to within a hair of the first pandemic since 1968. Some important points on the timeline of H1N1 swine flu.
An H1N1 swine flu virus containing swine, avian and human genes is recognized in pig populations in North America. This virus will later be recognized as a parent of the new swine flu.
March 31 - A clinical trial designed to assess the efficacy of a new rapid diagnostic test for influenza finds an untypeable flu virus in a sample from a person from the San Diego area. Public health is alerted and the virus is sent for testing in Wisconsin and later to the U.S. Centers for Disease Control.
April 17 - The CDC informs the World Health Organization it has found a case where an H1N1 swine flu virus infected a person in California. The virus is similar to the triple reassortant but with two swapped genes. Human infection with animal flu viruses signals a pandemic threat and WHO alerts member states.
April 17 - The head of Mexico's national microbiology lab emails Dr. Frank Plummer, head of Canada's national lab in Winnipeg, asking for help figuring out what is behind outbreaks of severe respiratory disease in parts of Mexico. Plummer offers assistance.
April 20 - The Public Health Agency of Canada warns quarantine services to be on the lookout for sick travellers returning from Mexico.
April 21 - The CDC issues an advisory revealing it has found two human swine flu cases in California. The WHO says it is watching.
April 22 - Specimens from Mexico arrive at the Winnipeg lab shortly before lunch. Within 24 hours researchers there realize at least some of the Mexican cases are human infections with the H1N1 swine flu virus.
April 23 - The CDC says they've found seven swine flu infections, in California and Texas.
April 24 - Mexico informs the WHO the Winnipeg lab has confirmed H1N1 swine flu is causing disease in Mexico.
April 26 - Officials in Nova Scotia and British Columbia announce Canada's first swine flu cases.
April 27 - The WHO raises the pandemic alert level to Phase 4 for the first time since the scale was created. Five countries have cases.
April 29 - The WHO raises the pandemic alert level to Phase 5, one away from a pandemic. It says the virus is spreading from person to person in both Mexico and the United States.