H3N2v outbreaks no cause for alarm, yet: CDC
Two outbreaks of influenza A (H3N2) variant virus in humans in Ohio and Indiana — one of which was and one of which may have been triggered by contact with swine — are being tracked by the Centers for Disease Control but are not yet a source of concern, says Dr. Joseph Bresee, chief of the Epidemiology and Prevention branch in the Influenza Division of the Atlanta-based agency.
Genetic testing at CDC confirmed that four people who became ill with flu had a strain of the virus that was nearly identical to that found in swine at the LaPorte (Ind.) County Fair, which all four patients had attended. The Indiana fair was held in early July; more recently a similar outbreak affecting as many as 41 children and adults occurred in Butler County, Ohio. The CDC is investigating to see if the virus in humans and that found in the swine at that county’s fair may be similarly linked, Dr. Bresee said.
He noted that it was too early to know whether the two outbreaks are related to one another.
In either case, Dr. Bresee notes that the influenza A (H3N2) variant of the virus is not new. It first was identified in August 2011. So far 17 people nationwide have been positively determined to have suffered from that particular version of the virus.
However, the H3N2 variant is not usually more virulent than a typical, average case of the flu. That is, some patients have been admitted to the hospital, but it is not particularly life-threatening to healthy adults, Dr. Bresee says. Also, while the virus, once picked up from contact with hogs, can be transmitted between humans, this variant loses steam within just a couple of generations and after that is no longer a threat.
In 2009, by contrast, the H1N1 outbreak killed at least 18,000 people worldwide, according to the World Health Organization.
As for H3N2, “Right now they’re just swine-origin viruses and it’s possible to infect humans, but at a pretty low level,” Dr. Bresee says. “There are more [outbreaks] now than in the past makes us look a little closer. When each of these [virus outbreaks] come up, if they do have some of these markers (such as life-threatening virulence), that make us worry more.”
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