Update: novel influenza A (H1N1) virus infection - Mexico, March-May, 2009

Abstract

On April 12, 2009, Mexico responded to a request for verification by the World Health Organization (WHO) of an outbreak of acute respiratory illness in the small community of La Gloria, Veracruz. During April 15-17, the Mexico Ministry of Health received informal notification of clusters of rapidly progressive severe pneumonia occurring mostly in Distrito Federal (metropolitan Mexico City) and San Luis Potosi. In response, on April 17, Mexico intensified national surveillance for acute respiratory illness and pneumonia. During April 22-24, novel influenza A (H1N1) virus infection, previously identified in two children in the United States, was confirmed in several patients. This report updates a previous report on the outbreak in Mexico and summarizes public health actions taken to date by Mexico to monitor and control the outbreak. During March 1-May 29, national surveillance identified 41,998 persons with acute respiratory illness; specimens from 25,127 (59.8%) patients were tested, of which 5,337 (21.2%) were positive for novel influenza A (H1N1) virus infection by real-time reverse transcription--polymerase chain reaction (rRT-PCR). As of May 29, 97 patients with laboratory-confirmed infection had died. Epidemiologic evidence to date suggests that the outbreak likely peaked nationally in late April, although localized cases continue to be identified.

FIGURE 1. Number of laboratory-confirmed cases of novel influenza A (H1N1) virus infection (N = 5,337)* and deaths (N = 97),† by state and Distrito Federal — Mexico, March–May 2009

* Reported as of May 29, 2009. † Indicated by numerals. Alternative Text: The figure above shows the number of laboratory-confirmed cases of novel influenza A (H1N1) virus infection (N = 5,337) and deaths (N = 97) by state and Distrito Federal in Mexico from March through May 2009. As of May 29, Distrito Federal (Mexico City) had the highest number of laboratory-confirmed novel influenza A (H1N1) cases (1,804) and deaths (38); Mexico State reported 21 deaths.

FIGURE 2. Number (N = 5,305) of laboratory-confirmed cases of novel influenza A (H1N1) virus infection,* by date of illness onset — Mexico, March–May 2009

* Includes all confirmed cases with onset data reported as of May 29, 2009. Does not reflect all cases because of a backlog of untested specimens. Alternative Text: The figure above shows the number (N = 5,305) of laboratory-confirmed cases of novel influenza A (H1N1) virus infection, by date of illness onset in Mexico from March through May 2009. The peak number of confirmed cases (375) had onset of April 27. As of May 29, all states in Mexico had reported laboratory-confirmed cases of novel influenza A (H1N1) virus.