- Two new studies present evidence that the virus causing
severe acute respiratory syndrome (SARS) may spread through the air, not
just through direct contact with contaminated water droplets as previous
research had shown.
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- SARS coronavirus was detected in the air in a patient's
room during the 2003 outbreak in Toronto, according to a new study published
in The Journal of Infectious Diseases. Another study, from Hong Kong, shows
patients in hospital bays near a SARS patient had a much higher infection
rate than patients in distant bays, consistent with the possibility of
airborne SARS transmission, according to an article in Clinical Infectious
Diseases. Both articles are published in the journals' May 1 issues, and
are now available online.
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- The Toronto research was conducted by Timothy F. Booth,
PhD and colleagues during the SARS outbreak there in March 2003. Their
results mark the first experimental confirmation of the presence of the
SARS virus in the air of an infected patient's hospital room.
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- The authors cautioned that their results do not document
any cases of airborne transmission of the SARS virus from one person to
another, only the dissemination of the virus from an infected patient to
the air, via breathing or coughing.
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- During the outbreak in Toronto hospitals, health care
workers became infected with the virus despite observance of strict infection
control precautions. The investigators wondered whether environmental contamination
of hospital air or surfaces could explain the ongoing risk of SARS coronavirus
transmission to health care workers. To answer this question, they collected
patient information and environmental samples from the SARS units of four
Toronto hospitals.
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- SARS coronavirus was detected in the air in one of the
four rooms tested. The researchers also detected virus in four of 85 surface
samples taken from frequently touched surfaces, highlighting the importance
of strict adherence to infection control precautions to prevent SARS coronavirus
transmission in the health care setting.
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- In the Hong Kong study, which focused on the 2003 SARS
outbreak at the Prince of Wales Hospital, 41 percent of patients admitted
to the ward in which the first SARS patient was staying became infected.
Proximity to the bed of the first case seemed to be strongly linked with
incidence of infection-two-thirds of patients in the same bay and half
of patients in an adjacent bay were infected with SARS, while only 18 percent
of patients in distant bays were infected.
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- The Hong Kong researchers, led by Ignatius T.S. Yu, MBBS,
MPH, of the Chinese University of Hong Kong, speculate that the increased
risk of infection with closer proximity to the index SARS case suggests
airborne transmission. Although they do not have "direct proof"
of airborne transmission, according to Dr. Yu, "no other known routes
of infectious diseases transmission could adequately explain the spread
of the disease in the outbreak, and hence we feel that the evidence is
quite strong."
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- An editorial accompanying the Toronto study, by Tommy
Tong, MBBS, of Princess Margaret Hospital in Hong Kong, emphasized the
scientific significance of discovering SARS coronavirus in the air in a
patient's room. "Although the possibility of airborne dissemination
of SARS coronavirus has been controversial," said Dr. Tong, "this
important work shows beyond doubt that SARS coronavirus aerosol generation
can occur from a patient with SARS." The Hong Kong study provides
additional, complementary evidence that the virus may be capable of spreading
through the air.
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- © Copyright IDSA 2005
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- http://www.idsociety.org/Template.cfm?
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