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The key to controlling a SARS outbreak is prompt detection of cases
and their contacts, followed by rapid implementation of control measures.
Identification of SARS cases is the basic step in prevention efforts,
whereas contact tracing provides a means to focus case-finding and containment
efforts on persons who are at greatest risk of SARS-CoV disease. Two
features of SARS-CoV disease pose challenges for case surveillance. First,
the early signs and symptoms are not specific enough to reliably distinguish
SARS-CoV disease from other common respiratory illnesses. Second, existing
laboratory diagnostic tests are not adequately sensitive early in the
course of illness. Therefore, risk of exposure (i.e., to another case
of SARS-CoV disease or to a setting where SARS-CoV transmission is occurring)
is key to considering the likelihood of a diagnosis of SARS-CoV disease.
Potential
sources of SARS-CoV for future exposures include persistent infection
in previously ill persons or reintroduction to humans from an animal
reservoir. In the absence of SARS-CoV transmission worldwide, the
most likely sites of recurrence are the original site of introduction
of SARS-CoV from animals to humans and locations where person-to-person
SARS-CoV transmission previously occurred. Laboratories that contain
live SARS-CoV could be a source of further transmission if compromised
laboratory techniques result in laboratory-acquired infections (see Singapore Ministry of Health report  and report from the Department of Health, Taiwan).
Because persons with SARS-CoV disease tended to appear in clusters
(e.g., in healthcare facilities, households, and a few special settings)
during the 2003 outbreaks, early signals of the reappearance of the
illness in U.S. communities could include unusual clusters of unexplained
pneumonia.
In the presence of person-to-person SARS-CoV transmission anywhere in
the world, patients with SARS-CoV disease or sites of SARS-CoV transmission
become the most likely sources of exposure. Contact tracing, the identification
of persons who had contact with a potential case of SARS-CoV disease
or may have been exposed while present in locations (e.g., hospitals)
with known SARS-CoV transmission, is essential for the implementation
of appropriate measures to reduce further spread of the disease.
The overall goals of SARS surveillance are to:
- Maximize
early detection of cases and clusters of respiratory infections that
might signal the re-emergence of SARS-CoV disease while minimizing
unnecessary laboratory testing, concerns about SARS-CoV, implementation
of control measures, and social disruption.
- If
person-to-person SARS-CoV transmission recurs, maintain prompt and
complete identification and reporting of potential cases to facilitate
outbreak control and management.
- Identify
and monitor contacts of cases of SARS-CoV disease to enable early detection
of illness in persons at greatest risk.
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