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SARS Virus May Spread Easily on Flights

Encourage Passengers to Cover Mouth When Coughing, Sneezing
WebMD Health News

Dec. 17, 2003 -- The SARS virus spread rapidly around the world, mostly carried by infected travelers. On planes, fellow passengers might easily catch the infection, too.

A study published in this week's New England Journal of Medicine looked at the risk of transmission on board flights that carried people who were later diagnosed with SARS when the illness was reaching epidemic levels.

In SARS, or severe acute respiratory syndrome, symptoms begin an average of four days after exposure to an infected person.

Because SARS is transmitted through close contact, many passengers and crew wore facemasks to protect themselves, and many flyers were screened for symptoms, writes lead researcher Sonja J. Olsen, PhD, with the CDC's Emerging Infections Program in Nonthaburi, Thailand.

But during the early part of the SARS outbreak, people with SARS were allowed to travel.

In this study of three flights, the researchers found:

  • After one flight carrying one person with symptoms of SARS, 16 people developed SARS, and two probably had SARS; another four with SARS could not be interviewed. The newly infected people sat in clusters directly in front of or behind the SARS virus carrier.

This type of pattern of transmission is consistent with other transmitted respiratory illness onboard aircrafts, write the authors. The risk of infection was greatest in people seated in the same row as or within three rows in front of the carrier.

Some passengers may have been infected before they went on board; therefore, the identified SARS virus carrier might not have been the cause, writes Olsen.

  • On another flight carrying four people with symptoms of SARS, only one other person contracted the illness.
  • On the third flight, with one passenger who did not yet have symptoms of SARS, no illness was reported among other passengers or crew afterward.

Transmission seems to vary according to the phase of illness, writes Olsen. "It is likely that persons who fly during the incubation period (within 10 days before onset of illness) pose very little or no risk to other passengers."

During that incubation period, they will not have symptoms of the illness, she writes.

Regardless of these variables, there still is the possibility of a "superspreader" -- a person who, for unknown reasons, is predisposed to transmitting the virus to large numbers of people.

"Aircraft ventilation systems are believed to be highly efficient at keeping the air free of [germ]," writes Olsen.

The fact that only 45% of passengers were interviewed, despite intensive investigation by three health departments, illustrates the difficulties of studying transmission. This raises the possibility that more transmission occurred than was recognized.

Nevertheless, since in one flight the risk of catching the SARS virus was significant, it's prudent to take measures to reduce that risk, writes Olsen.

To protecting yourself from infections:

  • Frequently wash hands with soap and water or use alcohol-based hand rubs.
  • Avoid touching your eyes, nose, and mouth with unclean hands.
  • Encourage people around you to cover their nose and mouth with a tissue when coughing or sneezing.

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