The latest on H1N1 flu from the Harvard Health Letter

So far, the 2009 swine flu (H1N1) pandemic has been more widespread than lethal, notes the Harvard Health Letter. The novel H1N1 virus has some properties that seem to make it less capable of causing serious disease than had been expected.

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Seasonal flu tends to symptomatically infect (very roughly) between 5% and 20% of the population each year, whereas pandemics tend to cause symptomatic infections in 25% to 40% of the population. This H1N1 epidemic may not come up to that level, but it is a potential difference between pandemic and regular seasonal flu.

Boston, MA (Vocus) October 9, 2009

So far, the 2009 swine flu (H1N1) pandemic has been more widespread than lethal, notes the Harvard Health Letter. The novel H1N1 virus has some properties that seem to make it less capable of causing serious disease than had been expected.

At least early in the flu season, in the relatively rare instances when H1N1 has caused complications that result in hospitalization (and even more rarely, death), the people most likely to be affected have been young, especially school-age children, whereas older people seem relatively protected, reports the Harvard Health Letter.

The pattern for regular "seasonal" flu virus that circulates every winter is just the opposite: it's the old who are far more vulnerable to complications, which typically involve a secondary bacterial infection that causes pneumonia.

The explanation most often given for the difference is that older people may have some residual immunity from past exposure to H1N1 flu viruses--viruses similar to, but not exactly the same as, this year's novel H1N1.
Harvard experts discussed the latest on the H1N1 pandemic at a forum held on the Harvard Medical School campus on September 25. The video is posted here: http://hms.harvard.edu/public/h1n1/index.html.

"The good news is that virtually everything we have learned since the early days of this pandemic has pointed toward a lower level of concern," said Marc Lipsitch, an epidemiologist at the Harvard School of Public Health and a member of the H1N1 scientific advisory group to the White House.

Lipsitch said data collected in the United States show estimates for the death rate for H1N1 range between one death for every 2,000 symptomatic cases and one death for every 14,000 (which in percentage terms works out to 0.007%). In comparison, the death rate for seasonal flu is roughly one death for every 1,000 to 2,000 cases.

"But that's not the only point of comparison," said Lipsitch. "Seasonal flu tends to symptomatically infect (very roughly) between 5% and 20% of the population each year, whereas pandemics tend to cause symptomatic infections in 25% to 40% of the population. This H1N1 epidemic may not come up to that level, but it is a potential difference between pandemic and regular seasonal flu."

In its H1N1 coverage, the Harvard Health Letter gives several prevention recommendations:

  •     Get vaccinated.
  •     Don't shake hands.
  •     Wash your hands often.
  •     Cough and sneeze into your sleeve or into a tissue.
  •     Stay home if you have symptoms.
  •     Stock up on supplies (canned food, bottled water, some medicines) in case of social-distancing restrictions.

You can get more advice from Harvard Health Publications' new Swine Flu video: http://www.health.harvard.edu/flu-resource-center/swine-flu-precautions.htm.
Read the full-length article: "H1N1 and its descendents"

Also in this issue:

  •     Kids and video games
  •     Plasma therapy
  •     Toenail fungus
  •     Why take three blood thinners at once?

The Harvard Health Letter is available from Harvard Health Publications (http://www.health.harvard.edu), the publishing division of Harvard Medical School, for $29 per year. Subscribe at http://www.health.harvard.edu/health or by calling 877-649-9457 (toll-free).

Media: Contact Raquel Schott at Raquel_Schott (at) hms.harvard.edu for a complimentary copy of the newsletter, or to receive our press releases directly.

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