EMERGENCE OF SARS Table. Laboratory results for SARS patienta Characteristic Hemoglobin (g/dL) Leukocyte count (x109/L) Polymorphs (%) Lymphocytes (%) Monocytes (%) Eosinophils (%) Basophils (%) Platelets (x109/L) aSARS, severe acute respiratory syndrome. March 24 5.6 11.3 79.3 11.4 8.1 1.1 0.1 421 of his chest x-ray (Figure 2). On May 5, he was transferred back to Tan Tock Seng Hospital, an officially designated SARS hospital. The patient had no further temperature spikes and no respiratory symptoms, despite the chest x- ray abnormalities. Respiratory distress did not develop, and neither methylprednisolone nor ribavirin was given. The patient completed a course of imipenem but remains in hospital at the time of writing because of nosocomial sepsis. On April 8, his brother was also admitted to Tan Tock Seng Hospital for acute respiratory failure and died. Throat swabs from our patient were collected on April 4 and stool samples were collected on April 10, days 9 and 15 after the onset of fever, respectively. These samples were sent for viral studies that included virus isolation and reverse transcriptase–polymerase chain reaction (RT-PCR) for the SARS-associated coronavirus (SARS-CoV). Three sets of primers were used. The first two sets were SAR1S/As and BNIoutS2/As as described in the paper by Drosten et al. (7); the third primer set was Cor1/2 (5'-CAC CGT TTC TAC AGG TTA GCT AAC GA-3' and 5'-AAA TGT TTA CGC AGG TAA GCC TAA AA-3') from the Government Virus Unit, Hong Kong. From the throat swab, a weak band measuring 310 bp was found by using the Cor1/2 primer set only. Positive bands were seen with all three primer sets on the stool sample; the bands with the SAR1S/As and BNIoutS2/As primers measured 190 and 150 bp, respectively. The diagnosis of SARS in the patient’s brother was sub- sequently confirmed on April 9 when a throat swab was positive for SARS-CoV by PCR. Multiple postmortem samples were also positive for SARS-CoV by PCR, and SARS-CoV was also isolated in the lung tissue. Serum samples from the patient and the healthcare workers who were his contacts were tested for total anti- bodies to SARS-CoV with an enzyme immunoassay by using SARS-CoV Vero E6 cell lysate that had been devel- oped by the Centers for Disease Control and Prevention. Results of serologic testing were positive at day 41. Serum samples were taken from 14 of the 16 healthcare workers at least 21 days after onset of symptoms. Of these, 13 were positive for antibodies to SARS-CoV. March 25 7.5 8.99 83.0 8.1 5.3 0.6 0.3 459 March 28 9.4 8.39 77.3 14.3 8.2 0.1 0.1 332 March 30 10.9 10.07 81.4 13.8 4.5 0.1 0.2 286 Extensive epidemiologic studies identified this patient as the common source for the cluster of healthcare work- ers in Singapore General Hospital who were subsequently diagnosed with SARS. These healthcare workers were infected before chest infiltrates developed and the patient was isolated. A total of 16 healthcare workers (13 nurses, one health attendant, one radiographer, and one doctor), 12 patients, and eight visitors (including his brother) from the wards in which the patient was admitted were eventually diagnosed with probable SARS. In addition, he was linked to a clus- ter of five healthcare workers (one radiographer and four health attendants), one visitor, and three outpatients at the diagnostic radiology department where he had barium studies and an ultrasound performed. Epidemiologic evidence suggested that this patient was the source for this cluster. He was linked to one of the index cases in Tan Tock Seng Hospital, had the earliest onset of fever among the cohort of Singapore General Hospital probable cases, and was the only infected patient who had been in the two wards during the relevant time period. In addition, all the nurses infected had been assigned to care for him during the incubation period of their illness. Strong supportive evidence that could not oth- erwise be explained by contact with other patients comes from the cluster from radiology department. Conclusions We present this case to highlight the diagnostic as well as public health problems posed by a patient with a rather atypical SARS, whose illness was easily explained by a positive blood culture. Classically, SARS is described as an illness with an incubation of 2 to 7 days followed by a prodrome of high fever with headache, malaise, and myal- gia. At the onset of the illness, some patients have mild res- piratory symptoms. After 3 to 7 days, a lower respiratory phase with nonproductive cough or dyspnea begins (8). Although the clinical signs and symptoms in otherwise healthy persons are widely known, the full clinical spec- trum is not known. In the study by Lee et al., 78% of patients had abnormal chest radiographs at the onset of fever (4). Peiris et al. 350 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 2, February 2004