Molecular Advances in Severe Acute Respiratory Syndrome-associated Coronavirus (SARS-CoV)

Chow, Ken Yan Ching; Hon, Chung Chau; Hui, Raymond Kin Hi; Wong, Raymond Tsz Yeung; Yip, Chi Wai; Zeng, Fanya; Leung, Frederick Chi Ching

The first rapid real-time assay was developed based on the most conserved region of the ORF1b gene sequence (86 , 87 ) . A person will be confirmed to be infected by the SARS-CoV if viral RNA is detected by either the two PCR assays, two aliquots of specimen, or two sets of primers (http://www.cdc.gov/nci dod/sars/specimen collection sars2.htm). The sec-ond generation of this test protocol can detect the existence of the virus within 10 days after the onset of fever (87) (88) (89) and provides 80% sensitivity and 100% specificity in the testing of 50 NPA samples collected from SARS patients within three days after the onset of the disease (87 ) . To further increase the sensitivity, one-step real-time RT-PCR has been recently developed (89 ) . Specificity of the PCR can be enhanced by coupling it with the use of an additional amplification target using the virus N gene fragment (89 ) , which is theoretically the most abundant subgenomic mRNA produced during transcription (13 ) . The technique provides information on viral load during anti-viral treatments in real time, so that the efficacy of the therapy can be evaluated (10 ) . However, although the PCR assays are powerful, their performance is also technically demanding and labor intensive (10 ) .