Friday, April 24, 2009

WHO Considers Raising Pandemic Threat Level: Swine Flu Outbreaks in Southwest US and Mexico

Following the detection of 7 cases of swine flu in Texas and California last week, Mexico City officials requested the help of the WHO yesterday in investigating 130 suspected cases of swine flu. Reports vary on confirmed cases - but between 16 and 20 deaths from severe respiratory illness have been reported in Mexico in the last four weeks. Estimates of suspected cases spiked on Friday to between 800 and 900 in south and central Mexico and near Baja California Norte (which borders California). At least three of the US cases have been linked to the Mexican cases.

Though no numberes have been released, Mexican officials confirmed today that at least some of the deaths and other suspected cases are in fact the same strain of H1N1 found in Texas and California.

The unsusual strain of H1N1 virus includes genes from North American swine and avian influenza, human flu, and a European/Asian strain of swine flu. This strain is NOT related to H5N1 avian influenza, the strain that's circulating primarily in Southeast Asia and has caused concern about its pandemic potential over the past five years. Because human H1N1 viruses continually circulate among the human population, there may be some immunity to this strain by those previously infected with human flu. However, it's unclear how much immunity one could expect because this new H1N1 strain is made up primarily of swine flu genes.

"Reports suggest the majority of the cases are occurring in young, previously healthy adults in their mid 20s to mid 40s. There are said to have been over 800 cases so far, but it remains unclear if all of those people are sick with this virus or if other flu or respiratory viruses are also circulating and muddling the picture.

Mr. Hartl said the WHO is sending staff to Mexico to help authorities there get a better handle on the scope of the problem. “We're extremely concerned because we're looking at five different influenza events which may or may not be connected,” he said, referring to California, Texas and three possibly linked outbreaks in Mexico.""The world is currently at level 3 of the WHO's six-rung pandemic alert ladder, because of ongoing sporadic cases of human infection with the H5N1 avian flu virus. Phase 3 means there are occasional human cases with a novel flu virus. WHO would need the advice of an expert panel to move up to Phase 4 or beyond. Phase 6 is a pandemic."

Mexican health officials, the WHO, the US Centers for Disease Control and Prevention, and Canadian health ministries are working in collaboration to get a handle on the confirmed/suspected cases in Mexico.

CDC is holding a press briefing on the outbreak at 2:30 pm. We will provide updates as appropriate throughout the day.

For more from CDC:

For the full story see these related articles:

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