April 12, 2012
Updated: April 12, 2012 | 7:33 pm
New case of swine H3N2 flu found in U.S. child
By Helen Branswell The Canadian Press
TORONTO – After a lull of several months, an influenza virus that is sporadically jumping from pigs to people in the United States has made yet another appearance.
U.S. public health officials have reported a new human infection with the swine-origin H3N2 virus — officially called H3N2v (for variant) virus. The case is a young girl living in Utah; she is the 13th person known to have been infected with this new virus since it was first spotted last July.
Twelve of the 13 cases have been children under 18. In this case, state officials are asking that the girl’s precise age not be revealed.
She was taken for medical care because of a fever in late March. When she tested positive for influenza she was given the flu drug oseltamivir, or Tamiflu, and has since recovered. Members of her family and close contacts were tested for flu, but no additional cases were found.
The girl is believed to have become infected when she visited a swine processing plant in the week before she became ill, Dr. Michael Jhung of the Centers for Disease Control said in an interview.
This is the first of these cases seen in Utah, and the farthest west this virus has been spotted. Previous human cases have been reported in Indiana, Pennsylvania, Maine, Iowa and West Virginia.
About half of the cases had some exposure to pigs. But the rest did not and the CDC has acknowledged some limited person-to-person spread of the virus has likely taken place in some of these infections.
Utah is not a major pork producing state. In fact, it ranks 27th in hog production, according to the U.S. National Pork Producers Council. But the processing plant the child visited handled pigs from other states, Jhung said. He declined to specify which ones, referring the question to the U.S. Department of Agriculture.
A department spokesperson said via email Thursday that an investigation is ongoing and that information is still being gathered, “but there is no indication that there were ill pigs at the plant.”
The new H3N2v case is the first spotted since November.
Flu experts are keeping a close eye on this virus, which contains a gene from the 2009 pandemic H1N1 virus; that gene, the M gene, is believed to enhance the ability of flu viruses to infect people.
It remains unclear what kind of a threat the swine H3N2 — a distant cousin of the human H3N2 virus — poses to people.
A study published Thursday by CDC scientists reported that children under 10 are likely to be the most vulnerable, as an age group, to this virus.
By testing blood samples for antibodies that react to the virus, the scientists saw cross-reactive antibodies in about a third of samples from people aged 18 to 49, and in about 17 per cent of people 65 and older. They did not test samples from people aged 50 to 64.
That’s not an enormous amount of protection, and the scientists caution that antibodies that react to a virus may not necessarily protect against it.
“We can’t rule out that a proportion of older children and adults would be susceptible,” said Jacqueline Katz, chief of the immunology and pathogenesis branch of the CDC’s flu division, who was one of the authors of the study, published in the CDC’s Morbidity and Mortality Weekly Report.
Still, Katz noted that the percentage of adults with cross-reactive antibodies to H3N2v is similar to the percentage of seniors who had antibodies that reacted to pandemic H1N1 in 2009. And the experience from that pandemic was that people aged 65 and older were not as susceptible to H1N1 as younger adults and children.
The CDC results are similar to those reported in late January by Canadian researchers. But the Canadian group, led by Dr. Danuta Skowronski at the British Columbia Center for Disease Control, found that cross-reactive antibody levels were highest among young adults, and dropped off sharply around age 40.
“We do see that it drops from 20 to 29 to 30 to 39, and then a big drop from 40 years of age,” Skowronski said.
Katz said her group’s study had too few blood samples to analyze by smaller age groups. But she said they are doing a larger study now.
Skowronski’s group has already done a study analyzing 1,000 blood samples, 100 each per 10-year age span. Because the findings have been submitted to a medical journal for publication, she cannot go into detail about what they saw.
But she suggested H3N2v bears watching. “Don’t dismiss this virus. This virus could still be a player.”
http://metronews.ca/news/world/102292/n ... -us-child/
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