WHO, CDC Revise SARS Case Definition
Coronavirus Testing Now Included in SARS Diagnosis
May 1, 2003 -- As the number of SARS cases continues to climb in China, health officials from the World Health Organization (WHO) and the CDC have revised the case definition of SARS (severe acute respiratory syndrome) to include a diagnostic test to detect the virus -- and antibodies to the virus -- believed to cause the disease.
Worldwide, 5,865 probable SARS cases have now been reported to the WHO, including 391 deaths -- an increase of 202 cases and 19 deaths from yesterday. China continues to harbor more SARS cases than the rest of the world combined. Chinese officials today reported 187 new SARS cases and 11 deaths, and more than half of those new SARS cases were in the capital, Beijing.
Health officials say the future of SARS now largely depends on whether the disease can be controlled in China over the next few months. The WHO says hospitals in China's poorer provinces may not be able to handle the continued spread of SARS and may require support.
By adding laboratory evidence of the SARS-related coronavirus to the SARS case definition, health officials hope more effectively to dismiss patients with illnesses caused by conditions other than SARS and develop better treatments.
According to the new case definition, a probable case of SARS is considered someone who meets all of the following diagnostic criteria:
High fever (over 100.4 degrees Fahrenheit);
- Respiratory symptoms, such as cough, difficulty breathing;
- X-ray evidence that suggests pneumonia or respiratory distress syndrome;
- A travel history within 10 days of the start of symptoms to an area where SARS is present or close personal contact with a known SARS patient; AND
- Laboratory evidence that shows the presence of the SARS virus or antibodies to it.
But officials admit that currently available testing methods for the SARS coronavirus are not foolproof. Each of the tests has certain strengths and weaknesses.
For example, PCR tests that scan for a small portion of the virus' genetic makeup are faster than viral culture or antibody tests, but they are less precise than the more traditional and time-consuming methods and, therefore, may produce a false positive or negative result.
For those reasons, officials urge healthcare providers not to dismiss the possibility of SARS or downgrade a patient's status while waiting for the results of laboratory testing or based on a negative test result.
In fact, of the 52 probable SARS cases reported to the WHO by the CDC as of April 29, only six are laboratory confirmed using the new criteria. Twelve of these cases are considered probable but have not been confirmed because either the laboratory test was not sensitive enough or the SARS virus did not cause the illness.
According to the CDC, laboratory testing is in progress, undetermined, or pending suitable samples for the remaining 34 cases.
The WHO is working with a German institute to provide standardized diagnostic tests for SARS in an effort to improve the reliability of the tests.