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Early stages
December 2005 to January 2009: The Centers for Disease Control and Prevention receives reports of 12 cases of human infection with swine flu. Five of these 12 cases occurred in patients who had direct exposure to pigs and six reported being near pigs. Exposure in one case is unknown. -
First U.S. case
Believed to be the date of the earliest onset of the swine flu cases in the U.S., Dr. Nancy Cox of the CDC said in an April 23 press briefing. -
4-year-old ill in Veracruz
A 4-year-old boy contracted the virus before this date in Veracruz state, Mexican Health Secretary Jose Angel Cordova later said citing test results. A community in Veracruz has been protesting pollution from a large pig farm. -
La Gloria health alert
Local health officials declare a health alert due to a respiratory disease outbreak in the Mexican town of La Gloria in Veracruz state. Health officials record 400 cases of people who sought medical treatment in the previous week in the town. About 60 percent of the town of 3,000 are affected. -
2 children infected in southern California
CDC determines that two children in adjacent counties in southern California had illnesses caused by infection with swine flu. Both children became sick in late March. -
First Texas cases, more in California
CDC confirms three additional cases of swine flu in California and two in Texas, near San Antonio. -
16 hospital workers sick in Oaxaca
The Oaxaca Health Department indicates that 16 employees at the Hospital Civil Aurelio Valdivieso have contracted respiratory disease -
Deaths confirmed; Mexico City shuts down
Mexico's Minister of Health confirms 20 deaths from swine flu, but 40 other fatalities were being probed and at least 943 nationwide were sick from the suspected flu. Mexico City shuts down schools, museums, libraries, and state-run theaters across the capital. -
Cases grow across North America
The number of confirmed cases in the U.S. climbs to 20 in five states. Mexico reports suspect clinical cases have been reported in 19 of the country's 32 states. Canada confirms six cases. -
Human-to-human transmission identified
The World Health Organization raises its pandemic alert status to Phase 4, meaning there is sustained human-to-human transmission of the virus causing outbreaks in at least one country. -
1,995 possible cases in Mexico; 48 confirmed in U.S.
Mexican Health Secretary Jose Angel Cordova said 1,995 people have been hospitalized with serious cases of pneumonia since mid-April and about half of those have been released. The government does not yet know how many were swine flu. The CDC reports the suspected death toll in Mexico has climbed to 149. The number of confirmed cases in the U.S. climbs to 48 in five states. -
Cuban travel ban
Cuba suspends flights to and from Mexico, becoming the first country to impose a travel ban.
