New studies that show the SARS virus can lurk for hours and even days in various environments could help scientists learn more about how the disease spreads.
The virus can survive on plastic surfaces for two days, linger in human feces for up to four days and withstand cold for three weeks, according to the research.
This has prompted a top World Health Organization official to warn of the possibility that SARS could hide on hospital surfaces, within refrigerators or on unwashed hands. The data could help explain the SARS infections of more than 200 people at a Hong Kong apartment complex with a faulty sewage system, he added.
"There has been speculation that the touching of objects could be involved," the WHO's chief SARS scientist, Klaus Stohr, said in an interview with The Washington Post. "This shows that transmission by contaminated hands or contaminated objects in the environment can play a role."
Yet Toronto experts emphasized that Canada's precautions remain more than adequate, given that the vast majority of cases of severe acute respiratory syndrome result from infected people coughing or sneezing on others. And just because viruses can exist in the open environment doesn't necessarily mean that they do so in concentrations high enough to actively infect people, the experts said.
"If you have a good sanitary infrastructure and you're washing your hands, it does not seem to be an issue in Toronto," Elizabeth Rae of Toronto Public Health said in an interview yesterday.
"Even if it seems to be an issue in some places, the respiratory droplets seem to be the most important."
These remarks were backed up by two members of Toronto's SARS-containment team.
Donald Low, chief microbiologist at Mount Sinai Hospital, said the new studies might help SARS teams around the world understand the relatively few cases that haven't been linked to face-to-face contact. But he added that environmental contaminations could spell trouble for the developing world, where hospitals can't afford precautions such as isolation rooms.
Allison McGeer, head of infection control at Mount Sinai, said the studies correspond with current understandings of viruses such as SARS and precautions around Toronto remain more than adequate.
"Environmental transmission might be an issue," she said. "But we tend to systemically overestimate it."
Yesterday, the results of various studies done by scientists around the world were published on the WHO's Web site. They included the finding that SARS can survive in regular feces and urine for a day or two, but up to four days in diarrhea, which is more acidic.
This point lends credence to the theory that a leaky sewage system in a 33-floor Hong Kong high-rise called Amoy Gardens may have been responsible for more than 200 suspected SARS cases involving people from that building.
The studies also found that the SARS virus can linger on plastic surfaces for up to a day at room temperature, but for up to three weeks at lower temperatures ranging from 4 to -80 degrees.
"The most exciting, or perhaps most disturbing, finding is the virus stays alive in feces for as long as four days at room temperature," Dr. Stohr said in the published interview.
"The finding is the most disturbing one because it would suggest that fecal-oral transmission could take place."