Wednesday, May 6, 2009

Andrew Pekosz, an associate professor of molecular microbiology and immunology at Johns Hopkins University's Bloomberg School of Public Health in Baltimore, answers questions about swine flu.

-- Shankar Vedantam

Could you please explain why, if H1N1 is not known to be either more contagious or more lethal than the regular annual flus, it is causing such an aggressive response? Is it because since it's an unknown bug, its characteristics are unknown, so it's proper to energetically prepare for the worst-case scenario? Would you say the response -- both public and at the level of professional public health -- has been measured or paranoid?

The public health response so far has been measured and appropriate. Look at it this way: Every year, 36,000 people in the United States die from seasonal influenza, even though we vaccinate people and a good portion of the population (let's say 50 percent for discussion purposes) has some immunity to the circulating influenza virus strains. We know that swine H1N1 does not "resemble" human H1N1 very closely, so there is most likely little to no immunity to it in humans. Therefore, even if it is no more lethal than seasonal flu, twice as many people could get infected next year because we lack immunity to the virus. That means that 72,000 people could die from this strain of flu. Now, I'm not making predictions, just giving you an example of how a new influenza virus with mild disease potential could cause significant disease in the human population. The pandemics we should be comparing swine flu to are the ones in 1957 and 1968, not the one in 1918.

We have a nearly 5-month-old infant. If we or someone else transmits swine flu to her, how life-threatening could this be?

Influenza disease is most severe in the very young (less than 2 years old) and the senior population (more than 50 years old), but we don't know if this risk will be increased with swine flu infections. It doesn't appear so at this time.

Does the flu shot I had in December help prevent this flu?

The seasonal influenza vaccine will not provide much, if any, protection against swine flu. However, it did help prevent you from getting seasonal influenza.

Further questions? E-mail health@washpost.com.

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