SARS can live on common surfaces By Rob Stein, The Washington Post
The SARS virus can survive on common surfaces at room temperature for hours or even days, which could explain how people can catch the deadly lung infection without face-to-face contact with a sick person, scientists have found. NEW LABORATORY STUDIES, being released today, have produced the first scientific data on how long the SARS virus can live in various places and conditions, demonstrating for the first time that the microbe can linger outside an infected person's body. One study showed the virus survived for at least 24 hours on a plastic surface at room temperature, which suggests it might be possible to become infected from touching a tabletop, doorknob or other object. Another found the microbe remained viable for as long as four days in human waste, a crucial finding that could clarify how the virus can spread through apartment buildings, hospitals and other facilities. German scientists found a common detergent failed to kill the virus, indicating that some efforts to sterilize contaminated areas may be ineffective. An experiment conducted in Japan concluded that the virus could live for extended periods in the cold, suggesting it could survive the winter. The long-awaited findings should be crucial for containing the epidemic, and they could solve one of the most important mysteries about the new disease: how the virus spreads without direct exposure to infected individuals. "It's the first time we have hard data on the survival of the virus. Before, we were just speculating," Klaus Stohr, the World Health Organization's top SARS scientist, said yesterday. "There has been a lot of speculation that the touching of objects could be involved. This shows that transmission by contaminated hands or contaminated objects in the environment can play a role." In addition, the findings will help researchers develop better tests for the virus and possible treatments. Now that they know what temperatures kill the virus, researchers can purify serum from sick people to use in calibrating tests and possibly to give other patients as a therapy. Serum contains antibodies that are measured by tests. In addition, the antibodies could work as a treatment if they can neutralize the virus. CASES INCREASE The new data come as the number of cases continues to increase. An additional 191 cases and 18 deaths were reported yesterday, bringing the toll to 6,234 cases in 27 countries, and 435 deaths, according to the WHO. Outbreaks appear to be under control in Hanoi, Hong Kong, Singapore and Toronto, but the disease was still spreading in many parts of China, and Taiwan has experienced a sharp jump in cases in the past week. U.S. health officials are investigating 54 probable cases in this country, including three in Virginia, and are monitoring an additional 237 suspected cases. The results were produced by laboratories in Hong Kong, Japan, Germany and Beijing that are part of a scientific network organized by WHO to study the previously unknown virus. The findings were compiled and analyzed over the past few days and were to be posted on WHO's Web site today so public health workers around the world can begin using them to keep the virus from spreading, said Stohr, who described the findings in a telephone interview. "These studies are very important for designing strategies for cleaning and disinfecting," Stohr said. Stohr stressed that a key unknown is how much virus is necessary for someone to become infected. So even though the virus can survive in the environment, it remains unknown whether it can survive in sufficient quantities to be dangerous, he said. "What we're seeing is that this virus certainly has the capacity to stay in the environment. What we don't know is the infectious dose," he said. Stohr also emphasized that by far, the primary mode of transmission was through droplets that spray out when an infected person sneezes or coughs. ALTERNATIVE TRANSMISSION ROUTES But researchers had become increasingly suspicious that there were alternative transmission routes because of incidents in which people became infected without close personal contact with a sick person. The most disturbing case involved a 33-story apartment tower in the Amoy Gardens complex in Hong Kong. Hundreds of people living in the building were infected, forcing authorities to evacuate the residents to quarantine camps. An intensive investigation concluded that the outbreak may have been caused by a man who caught SARS, developed diarrhea and used his brother's bathroom in the building. Investigators found a small crack in a sewage pipe in the building and speculated that the virus spread through the building in droplets that became airborne from the leak. "There has been a lot of speculation about how the Amoy Gardens got infected. No one knew whether the hypothesis would hold. This would support the theory that ... sewage coming out from that crack could have contaminated the air," Stohr said. In the new research, scientists in Hong Kong mixed virus into normal human adult feces and diarrhea, as well as feces from a 6-month-old baby. The virus survived in the baby's feces for three hours, in normal feces for six hours, and in diarrhea for four days. The difference appears to be the acidity -- the virus survives longer as the acidity decreases, Stohr said. "This is important, because traces of stool could occur on surfaces in hospitals. So this is very important to know in sterilizing those environments," Stohr said. In another set of studies, scientists in Japan examined how well the virus weathered extreme temperatures. The virus died at 98.6 degrees Fahrenheit and above, started to deteriorate at 40 degrees but seemed to remain viable indefinitely when temperatures dropped to 32 degrees. Scientists in Beijing produced similar results. "This means that if the virus is being kept at lower temperatures, we have to think about next winter," Stohr said. German researchers, meanwhile, placed the virus on a plastic surface at room temperature and found it could survive as long as 24 hours. "It survived easily," Stohr said. Another team in Hong Kong produced similar results. The German scientists also found that a commonly used detergent appeared to have little effect on the virus. The U.S. Environmental Protection Agency is planning a large-scale study to test a large number of disinfectants against the virus, Stohr said. Other teams in Singapore and Hong Kong have also been testing the virus's ability to survive in various temperatures and levels of humidity; in blood; and on metals, plastics, paper and cotton. Those results could come within days, Stohr said. "We're beginning to understand how this virus can survive in the environment," he said. -- The silver-list is a moderated forum for discussion of colloidal silver. Instructions for unsubscribing may be found at: http://silverlist.org To post, address your message to: [email protected] Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <[email protected]>
