Severe Respiratory Disease in Mexico

Canada Issues Alert on Severe Respiratory Disease in Mexico
Recombinomics Commentary 02:22
April 23, 2009

The Public Health Agency of Canada has told quarantine services to be on alert for travellers returning from Mexico after a number of severe respiratory illnesses (SRI) were reported in some regions of the country.

PHAC, in an April 20 report, said Mexican officials informed the Canadian health agency that the "case-fatality rate was relatively high" and that most cases involved healthy adults between the ages of 25 and 44. A number of health-care workers were also affected.

Although no cause has been confirmed, some samples were positive for influenza A and B.

The above comments on an alert issued by Canada offer some insight into the situation in Mexico. The reports out of Mexico are decidedly mixed. Some reports describe an increase in influenza cases which is attributed to a late spike in influenza B, which when combined with influenza A, gives an abnormally high number of cases this late in the season. Other reports discuss revaccinating at risk groups with the current trivalent vaccine.

Samples have been sent to Canada for a comprehensive analysis.

The increased influenza-like illness and fatalities was announced as the CDC issued an MMWR dispatch on H1N1 swine flu. Two cases have been confirmed in children (9F and 10M) and family members had mild symptoms but were not tested. The precise location of the clusters in southern California has not been released, but one cluster is in San Diego Country, while the other is 100 miles away in Imperial County (see updated map). Additional suspect cases in Imperial County have been noted and it is likely that these cases are near the border with Mexico. Some media reports also note that some contacts have not been interviewed because they were in Mexico.

It remains unclear if these two outbreaks are related. All reported cases in California have been mild, and the two confirmed cases were influenza A positive, but failed to sub-type for seasonal flu. It is unclear if sub-typing failures have led to the confusing reports out of Mexico.

More information on these cases, and results of analysis in Canada, would be useful.

Similarly, a more precise location and number of confirmed and suspect cases in the United States would be useful.