Sustained Human Transmission of Swine H1N1 in California
Recombinomics Commentary 21:30
April 23, 2009
The above comments by the European Centere for Disease Control and Prevention on the confirmed H1N1 swine flu in southern California ignore the glaring indication of sustained human-to-human transmission, which is the distance between the two confirmed cases (see updated map).
There was no direct connection with swine or each other, so the confirmation of the same virus at distant locations was the indication, because both clusters were almost certainly caused by transmission from other humans.
Moreover, each confirmed case was linked to family members who developed symptoms before and after the confirmed case, supporting transmission within the family. However, because the symptoms were mild, none of the family members sought medical attention and were not tested.
Thus, the lack of evidence is simply due to the lack of testing, not the lack of transmission.
Yesterday there were reports of suspect cases in the Imperial Valley. It is likely that these cases will be confirmed and additional cases will be identified in both counties.
Moreover, it is also likely that there are additional cases in Mexico, which borders both counties. The relationship of the US cases to reported outbreaks of influenza and atypical pneumonia in Mexico remain to be determined, but the confirmed cases in California represent sustained transmission of a swine influenza in the human population, which is cause for concern.