August 1, 2012
The Butler County Health Department received 41 calls reporting that 39 children and two adults had become sick after attending the week-long fair, which ended Saturday, said director Pat Burg.
Most of the people who became sick with the suspected H3N2v (variant) influenza virus had direct contact with hogs at the fair, she said.
Vast majority of the 41 in contact with pigs. Might be children exhibiting or friends of children exhibiting
There were 350 hog exhibitors at the fair, Burg said.
H3N2v can be transmitted from swine to humans and vice versa, officials said, but it is rarely transmitted between humans.
The above comments confirm that the number of symptomatic people linked to the Butler County Fair in Hamilton, Ohio was markedly higher than the 10 confirmed cases, which are record numbers for confirmed or suspect H3N2v cases at a single event. These numbers increase the likelihood that the H3N2v in Ohio matches the LaPorte County Fair outbreak in Indiana were there were 4 confirmed cases and at least 15 symptomatic cases identified via telephone survey.
The comment that the H3N2v is rarely transmitted between humans is false. The sequences from the LaPorte County Fair were closely related to the sequences from the West Virginia daycare center in late 2011. Two cases were confirmed, but 23 contacts were symptomatic and there was no swine exposure. The H3N2v was transmitting person to person for about a month, leading to flu-like symptoms in 23 of 70 contacts.
Like the Butler County and LaPorte County fairs, the majority of symptomatic cases are not tested, but are epidemiologically linked.
The identity between the West Virginia cluster and LaPorte cluster indicate this novel sub-clade, which is distinct from the first 10 confirmed cases in 2011, has adapted to humans and is leading to record numbers of confirmed and symptomatic cases.
The limited number of confirmed or reported cases is linked to surveillance failures, not transmission efficiency.