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Paradigm Shift Intervention Monitoring
Match of trH3N2 Cases In PA and IN Raises
This report describes two cases of febrile respiratory illness caused by swine-origin influenza A (H3N2) viruses identified on August 19 and August 26, 2011, and the current investigations. No epidemiologic link between the two cases has been identified, and although investigations are ongoing, no additional confirmed human infections with this virus have been detected.
The above comments are from the special MMWR report issued today. Media reports indicate the two children are under the age of 2. The Indiana case matches the characterization sheet for A/Indiana/08/2011, which is a 1M collected on July 24, 2011. The sequences were deposited at GISAID by the CDC on August 24, 2011 and the MP gene was from pandemic H1N1. This combination of 7 trH3N2 genes and 1 H1N1 MP gene has not been reported previously.
The finding of the same constellation in a case in Pennsylvania (2F) a few weeks later indicates this virus is transmitting. The Indiana case had contact with a caretaker who had contact with swine. However, those attending state fairs have contact with others who may be transmitting this virus.
Both cases recovered, but had symptoms that generated a visit to the emergency department, raising concerns that milder cases are far more widespread than the two reported cases. To date about half of the confirmed trH3N2 cases have required hospitalization.
Although the H and N are human, they have been circulating in swine since the early 1990’s and are markedly different than current seasonal flu. Moreover, these sequences have D225G, which targets the lung.
Release of sequences from the Pennsylvania case would be useful, as would more information on suspect cases.