"Can humans catch swine flu?"
"Swine flu viruses do not normally infect humans. However, rare human infections with swine flu have occurred. In the past several years, CDC has
received, on average, about one influenza virus isolate from a human that tests positive for swine flu each year. Most commonly, these cases occur in
persons with direct exposure to pigs. In addition, there have been rare documented cases of one person spreading swine flu to others. For example, an
outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak
resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient."
"What are the public health implications of human infections with swine influenza viruses?"
"Human infections with animal influenza A viruses against which the human population has little immunity should be investigated to determine the
source of infection, and the extent of spread and evidence of human-to-human transmission. Influenza A viruses new to the human population that are
able to efficiently transmit from person to person and cause illness may represent a pandemic threat.
Although immunity to swine H1N1 viruses is low in the human population, a high proportion of persons occupationally exposed to pigs (such as pig
farmers or pig veterinarians) have been shown in several studies to have antibody evidence of prior swine H1N1 flu infection. And, for swine H1N1
viruses, only rare person-to-person transmission has been documented in the past. Thus, human infections with swine H1N1 viruses should be
investigated particularly when they are detected among nonoccupationally exposed persons to ensure that human-to-human transmission is not occurring
and to monitor for changes in circulating viruses. Because most persons have some antibody to influenza H3N2 viruses since H3N2 viruses occur commonly
in humans and because the swine and human H3N2 viruses are similar, swine H3N2 virus infections in humans would not represent a possible pandemic
threat."
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