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Commentary
Asymptomatic
Swine Linked To Indiana Veterinarian With trH3N2
Recombinomics Commentary 12:30
November 10, 2011
The above translation is from the travel warning issued by the Taiwan CDC regarding trH3N2 in the United States. The warning sourced the above information to the WHO Event Information Site for IHR National Focal Point dated 11/2.
The above dates and description of the trH3N2 case matched the characterization sheet associated with the sequences released by the US CDC for A/Indiana/10/2011 and subsequently reported by the Indiana State DoH and the US CDC.
Therefore, Recombinomics contacted Dr Bret Marsh, State Veterinarian at the Indiana State Board of Animal Health, who investigated the case. He noted that all of the swine recently contacted by the veterinarian had been asymptomatic for at least a month prior to contact, reducing the likelihood that these swine were the source of A/Indiana/10/2011.
Similar results had been reported for the caretaker for the first 2011 trH3N2 case (2M) from Indiana. The case had no swine contact and the caretaker, as well as the swine linked to the caretaker, were asymptomatic.
Similarly, the swine presented at the Washington County fair in Pennsylvania were asymptomatic.
Moreover, the disease onset dates for the two Maine cases reduces the likelihood of a swine origin for these case. The first case (8M) was from Cumberland county and he developed symptoms on October 7 (sample collected October 10). He attended a agricultural fair in the week prior to symptoms, which was almost certainly the Cumberland County fair, which ended October 2. The five day gap between the end of the fair and the disease onset dates reduces the likelihood that the swine were at source of A/Indiana/06/2011. The second case was also exposed to swine at an agricultural fair and since the second case lived in the vicinity of the first, his (also 8M) “exposure” was also associated with the Cumberland County fair, but he developed symptoms two weeks later (sample collected October 22) significantly reducing the likelihood that the swine at the fair were a source of his infections. Moreover, there have been no reports of symptomatic swine at the fair in Maine.
The absence of linkage to any symptomatic swine by any of the 7 confirmed cases is consistent with the sequence analysis of the isolates from the human cases, which share the same constellation of genes with each other, including an M gene from H1N1pdm09, which has never been reported in swine anywhere in the world, in spite of increased swine surveillance, including sequences from swine in Indiana and Pennsylvania collected in 2010 and/or 2011.
Moreover, the trH3N2 cases dominate the confirmed cases in the above states. The two trH3N2 cases in Maine represent the only two reported cases since July 2011. Similarly, the Indiana cases represent 2 of the 3 influenza cases in Indiana, while the Pennsylvania cases represent 3 of the 5 confirmed influenza cases in Pennsylvania.
Thus, the swine “exposure” is more closely linked to sample collection and testing than transmission from swine, which highlights the need for aggressive testing of cases without swine exposure, such as the atypical pneumonia cases in Shelby County, Indiana.
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