Introduction

SARS, in contrast to diseases like flu or rubella, is only moderately transmissible. The number of secondary SARS cases per index case, ranging in one epidemiologic study from 2.2 to 3.6, are considerably lower than those estimated for most other diseases with respiratory transmission (Lipsitch). This indicates that a combination of control measures, including shortening the time from symptom onset to isolation of patients, effective contact tracing and quarantine of exposed persons, can be effective in containing SARS. Indeed, such measures have been successful and have contributed to the prevention of major outbreaks in other countries. On the other hand, in the absence of such effective measures, SARS has the potential to spread widely (Lipsitch).

In the absence of a vaccine, the most effective way to control a new viral disease such as SARS is to break the chain of transmission from infected to healthy persons. In almost all documented cases, SARS is spread through close face-to-face contact with infected droplets when a patient sneezes or coughs (WHO, WER 20/2003).

For SARS, three activities − case detection, patient isolation and contact tracing − can reduce the number of people exposed to each infectious case and eventually break the chain of transmission (WHO, WER 20/2003):

1.Case detection aims to identify SARS cases as soon after the onset of illness as possible.

2.Once cases are identified, the next step is to ensure their prompt isolation in a properly equipped facility, and management according to strict infection control procedures.

3.The third activity − the detective work − involves the identification of all close contacts of each case and assurance of their care