While human infection with swine influenza viruses is rare, it can occur. This is most likely to occur when people are in close proximity to infected pigs, such as in pig barns and livestock exhibits housing pigs at fairs. Both of the patients with confirmed trH3N2 infection reported in FluView were in the vicinity of live pigs.
The above comments from the CDC update on the most recently reported H3N2 swine flu cases are carefully worded to give the impression that the cases were due to transmission of H3N2 from swine to humans, but the report itself gives no such data for the two most recent cases, and no such data has been presented for the three prior H3N2 cases. Moreover, there is no claim of contact for three of the five cases, and for the two cases with contact, there is no data indicating the contacted swine were symptomatic or infected.
Direct data has been presented for H1N1 infections at Huron County fair in Ohio in 2007. In that outbreak pigs at the fair were infected and H1N1 virus, A/swine/Ohio/24366/07 was isolated. Virus was also isolated from a presenter (10F), A/Ohio/01/2007, and her father (36M), A/Ohio/02/2007. 24 others at the fair had flu-like symptoms (in August in Ohio), and all human and swine sequences matched and were available at a public database.
However, these cases represent the bulk of evidence for transmission of H1N1 triple reassortants from swine to humans in the United States, although many of the symptomatic cases as well as one of the confirmed cases could have been infected by human to human transmission. A NEJM report described 11 cases infected with H1N1 triple reassortants, and only five (which included the two described above) had direct contact with swine. Two had no documented exposure, and four were in the vicinity of swine, but had no direct contact.
Weaker data has been presented for H3N2 cases, which occured after the 2009 H1N1 pandemic began. Only two of the five have been cited as having direct contact, and both cases are somewhat confusing.The first case was reported by the Kansas Department of Health and Environment (KDHE) and involved a child at the Riley County fair in July, 2009. The child developed symptoms in late July and sought medical care. The KDHE press release indicated the exhibitors were being questioned about the health of the swine at the fair. There were no reports that swine were ill, and no swine sequences from Kansas have been announced or made public. Continued:
• ProMED: Avian Influenza (51): Germany, LPNAI, H5N2, Duck, Goose (Link)
• Detected cases of H1N1 virus (Link)
• Namibia – Swine flu (Link)
• Reference Laboratory for Poultry Diseases yet to be upgraded (Link)
• Infection is imminent (Link)
• Outbreak of influenza type B in children – Ukraine (Zaporozhye) (Link)
• Doctors believe a flu pandemic in Ukraine will not. It will be the usual epidemic (Link)
• In late November, is expected flu epidemic (Link)
• Between 70 and 80% rebound pneumonia and bronchitis in Cabimas (Link)
• Recombinomics: Absence of Phylogenetic Analysis On Swine H3N2 Cases (Link)