A new H3N2 virus which includes a genomic segment from pandemic pH1N1, appears to have spread human to human in Iowa. This is apparently the same strain that previously infected people in Pennsylvania, Maine and Indiana.
From the Winnipeg Free Press, November 22, 2011
U.S. health officials have spotted three more children infected with a new swine-origin flu virus, this time in Iowa.
And while earlier cases of infection with this virus are believed to have been cause by exposure to pigs, this time the evidence points to person-to-person spread.
“There’s pretty good indications that one child gave it to the other two children,” Iowa state epidemiologist Dr. Patricia Quinlisk said in an interview from Des Moines.
“Right now we have every indication that there’s person-to-person spread and absolutely no indication whatsoever that there’s animal-to-human spread.”
The three children attended a small day-care together. They live in adjacent counties, Webster and Hamilton, in the centre of the state.
One became sick first and appears to have infected the other two. Quinlisk said it’s not clear how the first child got infected.
H3N2 viruses have been spreading in pigs for years. But this one is slightly different. It has picked up one of the genes from the H1N1 flu virus that caused the 2009 pandemic.
It’s not clear whether having that gene, the M gene, is helping this virus transmit to humans. But a study done in guinea pigs _ one of the animal models for influenza _ showed that the M gene from the 2009 H1N1 virus is critical to the pandemic virus’s ability to transmit well.
If this virus continues to spread human to human, a new flu pandemic has begun.