新型肺炎への対策、新展開

New York Times
March 05, 2003

http://www.nytimes.com/2003/05/05/science/sciencespecial/05INFE.html
?ex=1052712000&en=df0a23943e3feae6&ei=5062&partner=GOOGLE

New Findings on Weapons to Combat Deadly Virus
By LAWRENCE K. ALTMAN

New laboratory findings support the theory that the SARS virus can
survive up to four days on contaminated household surfaces like
toilets but that disinfectants like bleach are effective weapons
to kill it, the World Health Organization said yesterday.

The findings are important because doctors have determined that
people infected with the virus can excrete it in large amounts
in their stool and urine, raising the distinct possibility that
less than vigorous hygiene — particularly a lack of hand-washing
— can lead to its spread on surfaces in the home and elsewhere.

Health officials had assumed that this must be the case because
of the pattern of spread in an apartment complex and hotel in
Hong Kong. The new findings strengthen the theory, said Dr.
Klaus Stöhr, a German virologist and epidemiologist who is the
scientific director of the W.H.O.'s SARS investigation.

Researchers at The University of Hong Kong found that
disinfectants like bleach, ethanol, phenol, formaldehyde
and paraformaldehyde can kill the virus, the W.H.O. said.

The findings should give further confidence that such measures,
particularly in hospitals and homes where people who had contact
with SARS patients are quarantined, will work, Dr. Stöhr said in
an interview.

Hong Kong officials have found that 203 people with such contacts
who were in quarantine developed SARS, Dr. Stöhr said. Many of them
had had contact with people infected at Amoy Gardens, an apartment
complex where a large outbreak occurred. Hong Kong officials have
theorized that the outbreak resulted from a sewage leak.

Laboratory tests found that detergents were far less effective in
killing the SARS virus, Dr. Stöhr said.

The SARS virus is quite sensitive to changes in temperature, according
to researchers at the National Institute of Infectious Diseases in
Tokyo. At body temperature, the SARS virus survived less than four
days, the Japanese researchers found. But it survived at least four
days at refrigerator temperatures and seems to be able to survive
forever at temperatures in a deep freezer. On plastic surfaces at
room temperature, the virus could survive for two days, researchers said.

The findings lead to a hypothesis that if contamination of objects
in the environment plays a greater role than scientists have believed,
then seasonality will be an important factor in future outbreaks,
Dr. Stöhr said. But if face-to-face spread of respiratory droplets
plays the more important role in transmission, then the hypothesis
holds that SARS is less likely to be seasonal.

The SARS virus is a new member of the coronavirus family, which includes
viruses that can cause the common cold in humans and many more serious
diseases in animals. SARS researchers have tried to extrapolate findings
from known viruses in dealing with SARS.

But many aspects of the new findings are surprising. One is they show
that the SARS virus is less stable at room temperature than other
coronaviruses, particularly those that infect humans, Dr. Stöhr said.

Scientists still need to learn the minimum amount of virus that can
cause SARS, Dr. Stöhr said.

The new findings come from laboratory experiments that mimicked real-life
situations. Scientists found that the SARS virus could survive in feces
and urine for at least a day or two at room temperature, though for only
three hours in stool from babies.

In tests lasting 10 days, the SARS virus could survive for four days
in watery diarrhea. The difference in length of survival was due to the pH,
a measure of acidity, of the stool.

Scientists had known that infected individuals could excrete the SARS virus
(at least in the RNA, or an immature form) for up to 30 days after onset of
symptoms. But those findings reflected continuous production of the virus
in the body. The new findings pertain to a significant difference — stool
outside the body.

Dr. Stöhr said that researchers in Hong Kong were about to complete tests
to determine how long virus-contaminated feces could persist on various
surfaces like metal, cotton, plastic, even skin.

The new findings come from tests conducted by members of an international
network of laboratories that the W.H.O. assembled shortly after it issued
a global warning about SARS on March 12.