Questions and Answers About Swine Flu

Wednesday, April 29, 2009

We posed several questions, including some from readers, about the ongoing swine flu outbreak to Andrew Pekosz, associate professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health in Baltimore.

-- Shankar Vedantam

If I get myself infected by a mild version of swine flu, will that protect me against a more virulent form of the infection? One should never purposely try to get infected with any virus or bacterium -- there are simply too many things we don't know about animal viruses or bacteria and how they interact with humans.

There's a lot of Internet theorizing that this flu came from unsanitary hog farms. Does that seem plausible?

The swine A/H1N1 virus has genes from human, swine and avian influenza virus strains. An animal had to have been infected with three different kinds of influenza viruses to generate this particular virus. Housing farm animals together in common pens or yards is one way of transmitting viruses from one species to another. But such housing is not necessarily unsanitary; these are the most common ways small farmers keep their animals.

Although most of the transmission may be human-to-human, through respiratory secretions, is it biologically plausible that air blowing over pig wastes can carry the virus and infect people? Could contact with pigs or pig waste transmit the virus?

Influenza in pigs is a respiratory disease, so there is much less risk associated with pig waste. Swine farmers can get infected with swine influenza through exposure to respiratory secretions, but because swine A/H1N1 is spreading from person to person, the primary risk is from swine A/H1N1-infected people. In birds, the flu virus is primarily transmitted via the oral-fecal route, so there is a risk of exposure to avian influenza from an infected bird's waste. Exposure to any pork products or live swine is not a significant risk factor for acquiring swine A/H1N1.

Are we seeing more than one strain of swine flu virus? Are the current antivirals effective against what we are seeing?

All the data currently available indicate that there is only one strain of swine A/H1N1 responsible for all the confirmed human cases. This swine A/H1N1 is sensitive to the antivirals Tamiflu and Relenza.

Do Tamiflu and other medications work for children?

Tamiflu and Relenza are effective in children, but consult your family physician for the appropriate dosages.

Does swine flu have an incubation period? How long does it take, after a person is infected, for him or her to start showing symptoms?

In the United States, the symptoms associated with swine A/H1N1 infection are very similar to what we see with seasonal influenza. The incubation time is one to three days, and infected people are ill for two to four days.

It sounds as though medications such as Tamiflu have to be taken within 48 hours of infection for maximum efficacy, but how can patients know they have been infected before symptoms arise?

Drugs such as Tamiflu or Relenza should be taken within 48 hours of the appearance of symptoms, not from the time of exposure. If you begin to feel ill with flulike symptoms, call or see your physician.

If you were to guess, based on what we know about swine flu, would you say we are looking at a passing storm or the start of a pandemic?

It is so early in the outbreak that it is very difficult to predict. The biggest variable is whether the swine A/H1N1 will adapt or become more efficient at transmitting between humans. If it does, then that will set the stage for a pandemic. If it does not adapt further and public health control measures are strictly enforced, then this will most likely be contained.

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