Updated May 2, 2009 — How fast have things been moving in the current H1N1 swine flu outbreak? Follow the history of the emerging pandemic.
January 4-March 11, 2009
As part of its routine seasonal flu monitoring activities, Mexican health authorities collect 51 specimens positive for influenza A. They are later tested for swine flu at the CDC and all come back negative.
March 18
Cases of influenza-like illness (ILI) begin to be noted by health authorities in Mexico.
April 12
An outbreak of ILI is reported in the state of Veracruz, Mexico, east of Mexico City.
April 17
A case of atypical pneumonia in the state of Oaxaca, Mexico, in the south of the country, is reported. Mexican health authorities ask hospitals to report all cases of severe respiratory illness and collect laboratory specimens from them.
April 23
Following a steady rise, a total of 854 cases of pneumonia, presumably resulting from ILI, have been reported in Mexico City with 59 deaths.
Meanwhile, in San Luis Potosí, Mexico, north of Mexico City, 24 cases of ILI with 3 deaths have be reported, and in Mexicali, just south of California, four cases of ILI with no deaths have been reported.
These flu-like illnesses affect more healthy young adults and fewer of the very young and elderly than typical flu does. Several of them are laboratory confirmed as swine-origin influenza A (H1N1) virus of the same genetic strain as that detected in two children in California.
April 25
The Director-General of the WHO, Dr. Margaret Chan, declares a Public Health Emergency of International Concern.
April 26
CDC reports 20 laboratory confirmed human cases of swine influenza A/H1N1 from across the entire continental United States. All are classified as mild ILI with no deaths reported. Preliminary testing shows all have the same genetic makeup, and the virus is described as a new subtype of influenza A H1N1.
Mexican government reports 18 laboratory confirmed cases of swine influenza A/H1N1, with possible cases reported in 19 of the country's 32 states.
April 27
CDC lab confirmed human cases total 40 (0 deaths). Mexico lab confirmed human cases total 26 (7 deaths). Canada reports 6 cases (0 deaths). Spain reports 1 case (0 deaths).