In their report of a nosocomial outbreak of SARS, Monali Varia and associates1 describe 8 patients with SARS who had possible hospital exposure to unidentified individuals with the disease. This highlights the importance of diagnosing SARS, including mild cases, before it can spread to others.
A 78-year-old woman with paroxysmal atrial fibrillation, hypertension and diabetes mellitus was admitted to our hospital in April 2003 for symptomatic bradycardia. While she was under observation, an outbreak of SARS occurred in her ward. Nine days later, she exhibited fever (38.2°C) but no respiratory symptoms. Mild air-space consolidation of the right lower lobe was apparent on chest radiography. She had lymphopenia (0.3 х 109/L), but her platelet count and serum levels of lactate dehydrogenase and creatine kinase were normal. Three sets of samples of nasopharyngeal aspirate, stool and urine tested negative for SARS coronavirus by reverse-transcriptase polymerase chain reaction (RT-PCR) and virus isolation. Her fever subsided with empiric cefoperazone/sulbactam therapy, and she remained well. After discharge, we received the laboratory report for her day 15 titre for SARS coronavirus, which was significantly elevated (640).
This case illustrates the difficulty of diagnosing mild SARS. This patient did not fulfill the WHO criteria for SARS,2 which have a low sensitivity (26%).3 RT-PCR and virus isolation were not sensitive enough to detect the infection, and the disease was diagnosed only with seroconversion in the convalescent phase. Better diagnostic tests are needed in the early phases of the disease4 to prevent the spread of SARS to other hospital patients.
Hing Ming Cheng Timothy Kwok Department of Medicine and Geriatrics Tai Po Hospital Hong Kong, China
Footnotes
Competing interests: None declared.
References
- 1.Varia M, Wilson S, Sarwal S, McGeer A, Gournis E, Galanis E, et al. Investigation of a nosocomial outbreak of severe acute respiratory syndrome (SARS) in Toronto, Canada. CMAJ 2003; 169(4):285-92. [PMC free article] [PubMed]
- 2.Case definitions for surveillance of severe acute respiratory syndrome (SARS). Geneva: World Health Organization; revised 2003 May 1. Available: www.who.int/csr/sars/casedefinition/en/ (accessed 2003 Sep 17).
- 3.Rainer TH, Cameron PA, Smit DV, Ong KL, Hung ANW, Chan DPN, et al. Evaluation of WHO criteria for identifying patients with severe acute respiratory syndrome out of hospital: perspective observational study. BMJ 2003; 326: 1354-8. [DOI] [PMC free article] [PubMed]
- 4.Poon LL, Chan KH, Wong OK, Yam WC, Yuen KY, Guan Y, et al. Early diagnosis of SARS coronavirus infection by real time RT-PCR. J Clin Virol 2003;28(3):233-8. [DOI] [PMC free article] [PubMed]