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The first recorded case. In California
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Second case detected in California almost 130 miles away from the first case of infection, without a connection to the previous patient.
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The World Health Organization (WHO) declared a state of public health emergency of international interest.
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The United States declares a public health emergency as cases of swine flu increase.
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World Health Organization (WHO) raises the influenza pandemic alert to a level 4, which means that there has been human-to-human transmission of the virus.
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WHO raises the influenza pandemic alert to a level 5, indicating sustained community-level outbreaks in two or more countries within the same region.
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The WHO intensified the alert level for an influenza pandemic from phase 4 to phase 5 to indicate that a pandemic was imminent.
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The day that school suspension was highest in the spring stage of the pandemic. 980 schools suspended classes and 607 778 students were affected.
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WHO raises the influenza pandemic alert to a level 6. The outbreak is now being considered a global pandemic.
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Clinical trials began to evaluate the 2009 H1N1 influenza vaccine.
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The FDA announced the approval of four 2009 H1N1 influenza vaccines.
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Influenza activity reached its highest level in the weekly report of October 24, 2009, where 48 of 50 states reported widespread influenza activity.
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The World Health Organization (WHO) declared the pandemic and raised the global pandemic alert level to Phase 6, indicating that the virus was spreading in other parts of the world.
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WHO Director General Dr. Margaret Chan announces that the H1N1 outbreak has moved into the post-pandemic period.
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The WHO announced the end of the 2009 H1N1 influenza pandemic.
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A study published in the Lancet Infectious Diseases journal estimates that the global death toll from the pandemic ranges between 151,700 and 575,400.