WEDNESDAY, Dec. 17, 2003 (HealthDayNews) -- Severe acute respiratory syndrome (SARS) can be transmitted from one passenger to others on airplanes, concludes a new study by researchers from the U.S. Centers for Disease Control and Prevention.
The study, which appears in the Dec. 18 issue of the New England Journal of Medicine, is of particular concern because the World Health Organization (WHO) just reported the first new case of the deadly respiratory illness in months.
The victim is a senior research scientist from Taiwan, who may not have followed proper safety procedures while working with the virus, the Associated Press reported Wednesday. The 44-year-old man had recently traveled to a Singapore medical conference, although officials believe he contracted the virus in his Taiwanese lab. However, 70 people in Singapore who came in contact with him have been quarantined as a precaution.
The U.S. study, which focused on three flights known to carry SARS victims in last spring's global outbreak, does offer some hope, at least for air travelers. Out of the three flights studied, the disease spread rapidly on only one.
"The bottom line is that airline transmission of SARS can occur, but it looks like the overall risk is pretty low," says one of the study's authors, Sonja Olsen, chief of the epidemiology section of the International Emerging Infections Program for the CDC in Bangkok, Thailand.
Dr. Donald Low, chief of microbiology at Mount Sinai Hospital in Toronto, who wrote an accompanying editorial, agrees that the risk of transmission is often very low. "An important message is that some patients just don't transmit the disease," he says.
SARS first appeared in November 2002 in the Guangdong province of China. Early symptoms of the disease include fever, fatigue, chills, and coughing. As the disease progresses, there may also be shortness of breath, chest pain, and watery diarrhea.
It wasn't until two months later, in January, that outbreaks of the disease started to spread in mainland China, although government officials there did not report it to the world.
By February, the disease had spread to Hong Kong, Singapore, Taiwan, Vietnam and Canada. A month later, it moved into the United States; eventually it hit two dozen countries before officials declared the outbreak over in July.
In just seven months, SARS infected more than 8,000 people around the world and left 774 dead, according to a review article on SARS that accompanies the study in the journal.
Low says that the outbreak taught health officials many lessons and highlighted the need for a greater public health infrastructure to deal with infectious diseases.
"We live in an environment where there is the threat of global illness," he says.
And one of the easiest ways diseases get transported from country to country is via air travel. In the case of SARS, researchers found that sometimes just being on a plane with an infected person can get you sick.
Olsen says that she and her colleagues looked at the passenger data from three flights, all of which were known to be carrying at least one passenger infected with SARS.
On the first flight, the person who eventually developed SARS wasn't yet symptomatic and no one else on the flight became ill.
The second flight had someone with SARS who had fever and a cough at the time of travel. Twenty-two others became ill after the flight, according to Olsen. Many of those who became ill were sitting within three rows of the infected person.
The third flight carried four people with SARS who had had fever and coughing for several days before the flight, yet only one other person became ill after this flight.
Olsen says this study confirms one key thing: that there is still a lot to be learned about SARS.
No one really knows at what point people are infectious, she adds, and the study demonstrates that there are many variables that affect whether the disease transmits or not. Those include the length of the flight, the severity of the illness, or the proximity to the sick person.
Low says he's not concerned about a SARS outbreak recurring this year. He says the lessons learned from the initial outbreak should prevent the rapid spread of the disease seen last year.
Both Low and Olsen say simple preventive measures -- good hand washing and such respiratory etiquette as covering your mouth when you sneeze or cough -- can go a long way toward preventing infections.
Also, Low adds that if you've been traveling in a foreign country and are ill when you get home, make sure your doctor knows you've been traveling.
More information
For more information on SARS, visit the U.S. Centers for Disease Control and Prevention. To learn more about how infections spread, go to the Mayo Clinic.
