Methods for Monitoring in the Environment

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At this point, the knowledge level regarding the epidemiology and ecology of Severe Acute Respiratory Syndrome (SARS) is limited. While the initial SARS global outbreak of 2003 has been contained, the possibility of resurgence warrants a monitoring system that will detect SARS cases and indicate the re-emergence of the SARS-associated coronavirus (SARS-CoV) in the environment.

The primary method for detecting SARS-CoV in the environment is to rely on clinical recognition of SARS cases. The intensity of this surveillance system depends on the risk in that area. The World Health Organization (WHO) has defined three levels of risk and provides surveillance recommendations for particular areas based on their risk classification. The following is from the WHO document “Alert, verification and public health management of SARS in the post-outbreak period.”

Potential zone of re-emergence of SARS-CoV

  • Identified as source(s) of the previous outbreak in November 2002 or areas with an increased likelihood of animal to human transmission of SARS-CoV infection.
    • SARS Alert* AND
    • Enhanced surveillance for SARS AND
    • Special studies for SARS-CoV infections in animal and human populations

Nodal areas

  • Sustained local transmission experienced during the previous outbreak or entry of large numbers of persons from the potential zone of re-emergence of SARS-CoV
    • SARS Alert* AND
    • Enhanced surveillance for SARS

Low risk areas

  • Never reported cases, reported only imported cases or experienced only limited local transmission during the previous outbreak.
    • Surveillance for clusters of “alert” cases among health care workers, other hospital staff, patients and visitors in the same health care unit

*SARS Alert is designed to provide early warning of the potential recurrence of SARS and raise global alert if indicated

Definition of SARS Alert:
Two or more health care workers in the same health care unit fulfilling the clinical case definition of SARS and with onset of illness in the same 10-day period.
Hospital acquired illness in three or more persons (health care workers and/or other hospital staff and/or patients and/or visitors) in the same health care unit fulfilling the clinical case definition of SARS and with onset of illness in the same 10-day period.

Due to the difficulty in detecting SARS, the ability to detect SARS-CoV in the environment may be hindered.

Factors contributing to the difficulty of early detection of SARS include:

  • Lack of a current rapid diagnostic test that can reliably detect SARS-CoV in the first few days of illness
  • Seasonal occurrence of other respiratory diseases, including influenza