Special Articles: Review of Literature: General Infectious Diseases
Viral Shedding Patterns of Coronavirus in Patients With Probable Severe Acute Respiratory Syndrome
Viral Shedding Patterns of Coronavirus in Patients With Probable Severe Acute Respiratory Syndrome Cheng PKC et al. Lancet. 2004;363:1699
This is a report from Hong Kong on results of RT-PCR for detection of the SARS coronavirus RNA in 2134 specimens from 1041 patients with documented infection. The most frequently positive specimens were nasopharyngeal aspirates with a yield of 45% and stool with a yield of 28%. The peak time of positive results for nasopharyngeal aspirates was at 6 to 11 days after the onset of illness when 87 (58%) of 149 were positive. For stool, the peak was at 9 to 14 days. The overall results showed that the peak viral load was reached at 12 to 14 days of illness when patients were usually in hospital care making healthcare workers particularly vulnerable; the viral shedding was relatively low in the early stages of disease making diagnostic testing of low yield. The results for all specimens tested are summarized in the following table:
The authors conclude that the yield with this test is highly variable depending on the timing of the test and the specimen tested. The highest yield is at least 6 days after the onset of illness so that one of their recommendations is to test 6 days or later if the initial test is negative. High yield in stool presumably accounts for GI shedding as a potentially important role in transmission.© 2004 Lippincott Williams & Wilkins, Inc.