Evidence of Airborne Transmission of the Severe Acute Respiratory Syndrome Virus

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http://content.nejm.org/cgi/content/abstract/350/17/1731?

view=abstractpmid=15102999

Evidence of Airborne Transmission of the Severe Acute Respiratory

Syndrome Virus

Ignatius T.S. Yu, M.B., B.S., M.P.H., Yuguo Li, Ph.D., Tze Wai Wong,

M.B., B.S., Tam, M.Phil., Andy T. Chan, Ph.D., ph H.W.

Lee, Ph.D., Dennis Y.C. Leung, Ph.D., and Tommy Ho, B.Sc.

ABSTRACT

Background There is uncertainty about the mode of transmission of

the severe acute respiratory syndrome (SARS) virus. We analyzed the

temporal and spatial distributions of cases in a large community

outbreak of SARS in Hong Kong and examined the correlation of these

data with the three-dimensional spread of a virus-laden aerosol

plume that was modeled using studies of airflow dynamics.

Methods We determined the distribution of the initial 187 cases of

SARS in the Amoy Gardens housing complex in 2003 according to the

date of onset and location of residence. We then studied the

association between the location (building, floor, and direction the

apartment unit faced) and the probability of infection using

logistic regression. The spread of the airborne, virus-laden

aerosols generated by the index patient was modeled with the use of

airflow-dynamics studies, including studies performed with the use

of computational fluid-dynamics and multizone modeling.

Results The curves of the epidemic suggested a common source of the

outbreak. All but 5 patients lived in seven buildings (A to G), and

the index patient and more than half the other patients with SARS

(99 patients) lived in building E. Residents of the floors at the

middle and upper levels in building E were at a significantly higher

risk than residents on lower floors; this finding is consistent with

a rising plume of contaminated warm air in the air shaft generated

from a middle-level apartment unit. The risks for the different

units matched the virus concentrations predicted with the use of

multizone modeling. The distribution of risk in buildings B, C, and

D corresponded well with the three-dimensional spread of virus-laden

aerosols predicted with the use of computational fluid-dynamics

modeling.

Conclusions Airborne spread of the virus appears to explain this

large community outbreak of SARS, and future efforts at prevention

and control must take into consideration the potential for airborne

spread of this virus.

Source Information

From the Department of Community and Family Medicine, Chinese

University of Hong Kong (I.T.S.Y., T.W.W., W.T., T.H.); and the

Departments of Mechanical Engineering (Y.L., A.T.C., D.Y.C.L.) and

Civil Engineering (J.H.W.L.), University of Hong Kong — both in Hong

Kong, China.

Address reprint requests to Dr. Yu at the Department of Community

and Family Medicine, 4th Fl., School of Public Health, Prince of

Wales Hospital, Shatin, Hong Kong, China, or at iyu@....