Swine flu studied since the 1960s
Monday May 4, 2009 (foodconsumer.org) -- While public health officials are urging calm, emphasizing that the threat of the H1N1 virus may be easing, "we are not out of the woods yet," said Dr. Richard Besser of the Centers for Disease Control on a Fox News broadcast Sunday.
The CDC web site early Sunday listed 226 confirmed cases of the swine flu, which has spread into 30 states. But Bloomberg later reported that 241 swine flu cases had been reported in 34 states.
Dr. Anne Schuchat of the CDC was cited by Bloomberg as saying the increase may be due in part to a backlog of specimen and testing results.
On the international front, the World Health Organization stated on its website Sunday that 18 countries have officially reported 898 cases of H1N1 infection. In Mexico alone there are 506 confirmed human cases of infection, including 19 deaths. The increase is purportedly due to the fact that results from previously collected specimens are just now in.
Swine flu cases were also reported from Austria (1), Canada (85), China, Hong Kong Special Administrative Region (1), Costa Rica (1), Denmark (1), France (2), Germany (8), Ireland (1), Israel (3), Italy (1), Netherlands (1), New Zealand (4), Republic of Korea (1), Spain (40), Switzerland (1) and the United Kingdom (15).
Pigs are not believed to be the vehicles spreading the H1N1 virus in the outbreak; however, Canada reported on May 2 that the virus has been detected in a swine herd in Alberta. Nevertheless, WHO said the pigs likely got the virus from a Canadian farm worker who had recently returned from Mexico with flu-like symptoms.
And while the path and severity of the virus both remain unclear, scientists have been cautioning about the "pandemic potential" of the swine flu virus since August of 2002. Although cooked pork is believed to be safe to eat, a CDC funded study suggested that pigs can be the originators of a swine flu outbreak.
University of Wisconsin researchers, partly funded by the Emerging Infectious Disease department of the CDC, reported in 2002 that pigs had a definite role in generating genetically novel viruses, and even urged that monitoring swine farmers "might be prudent."
"Because pigs can play a role in generating genetically novel influenza viruses," wrote the researchers, "swine farmers may represent an important sentinel population to evaluate the emergence of new pandemic influenza viruses."
In the report, Dr. Christopher Olsen, leader of the study, referred to previous investigations into the swine flu virus done in the 1960s: "Previous studies by Kluska et.al in the 1960s suggested increased rates of infection among persons in contact with pigs or working with swine influenza viruses," he wrote, confirming the virus can come from the farm animals.
Olsen wrote that infections of humans with swine flu viruses were actually first verified by isolating swine influenza viruses from both pigs and their caretaker on a farm in southern Wisconsin in November 1976.
In the 2002 study, Olsen and his team evaluated "seropositivity," or a positive serum reaction to swine and human influenza viruses. The study included 74 swine farm owners and their employees in rural south-central Wisconsin. Participants included 44 men, aged 13 to 59 years, and 35 women aged seven to 57 years. The control group included 114 urban Milwaukee residents.
"The difference in the seropositive samples between the farm participants and urban control cohorts was statistically significant," says the study.
The positive reactions to the virus were "significantly associated with being a farm owner, or a farm family member, living on a farm, or entering the swine barn more than four days a week," said Olsen and his colleagues wrote. "In addition, pigs are clearly recognized as hosts in which genetic reassortment between human and avian viruses can produce novel strains of pandemic potential."
The researchers concluded that "given the frequency with which swine farm workers in our study were exposed to influenza viruses from pigs, close monitoring may be prudent.”
But it’s really unknown where the virus that caused the current outbreak came from.
(Written by Sheilah Downey and edited by Rachel stockton)
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