Friday, April 24, 2009

Swine Flu Outbreak

Breaking news today. Swine Flu is been affecting some state in the United States. This is very alarming. But what is a Swine Flu? What are the symptoms? Scientists are baffled and deeply worried by the latest outbreak of swine flu for two reasons: It appears to combine bird, swine and human viruses in a way that hasn't been seen before, and it is spreading from person to person. Although swine flu has been known to sporadically infect people, it has usually occurred in rare cases in which the virus jumps from swine to humans who are directly exposed to the animals, such as pig farmers. The virus that has surfaced in Mexico -- and apparently California and Texas -- is known as A/H1N1, a strain that hasn't been previously detected in pigs or humans. According to the Centers for Disease Control and Prevention in Atlanta, there have been some documented cases of a person-to-person jump. In 1988, for example, an apparent swine-flu infection in the U.S. was transmitted from a patient to health-care workers who were in close contact with the person. However, neither of the two California children diagnosed with the illness this spring had close contact with pigs. This, the CDC said, "increases the possibility that human-to-human transmission of this new influenza has occurred. "Not all pandemics are lethal, and it is far from clear whether the current swine flu infecting people could be the beginnings of a global outbreak. However, the World Health Organization is worried enough that it has alerted an expert panel that can recommend whether to raise the alert level for a global pandemic. New viral strains arise through a process called antigenic shift, or reassortment, when at least two viruses combine. This can happen when a cell is infected by two different flu viruses and some of their genes are exchanged during replication. Pigs are especially prone to be such "mixing vessels" since they can be infected by viruses that infect swine, birds and humans. Reassortment is often seen in water birds, especially ducks. Though these birds don't show symptoms, they shed the virus in their feces -- which could go on to infect pigs or possibly humans who come in close contact. The CDC said some of the genetic segments of the current swine-flu virus come from bird-flu viruses found in North America, plus one gene segment from a human-flu virus and two gene segments typically seen in pig-flu viruses in Europe and Asia. Symptoms are similar to those found in seasonal human flu, including fever, respiratory symptoms, nausea, vomiting and diarrhea. The virus is sensitive to both oseltamivir, a medication whose brand name is Tamiflu, and zanamivir, or Relenza. New viruses that emerge this way -- through antigenic shift -- have in the past been the culprits behind pandemics because they infect populations that have no immunity to the novel bug. Past pandemics, such as one that appeared in 1957 in Asia and another that surfaced in 1968 in Hong Kong, originated from flu viruses in birds. In recent years, public-health experts have been fearful about a potential pandemic triggered by the H5N1 bird-flu virus, which has spread from poultry to humans and killed several hundred people since 2003.

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