RESEARCH NPA became available to us in mid-March. We included in our study 218 patients who had nasopharyngeal RT-PCR performed at illness onset. Investigation Routine hematologic, biochemical, and microbiologic tests were performed for all patients. NPA samples were examined by rapid immunofluorescence antigen detection methods for viral cell culture and for common respiratory virus, including influenza viruses A and B; adenovirus; respiratory syncytial virus; and parainfluenza virus types 1, 2, and 3. Sputum samples were screened for bacterial and mycobacterial infection by conventional microscopic identification (Gram staining and acid-fast staining) and culture methods (blood, chocolate, MacConkey, and Löwenstein-Jensen media). Serologic testing for Mycoplasma pneumoniae, Chlamydia pneumoniae, and C. psittaci was performed. Urinary antigen detection tests were used to detect Legionella pneumophila and Streptococcus pneumoniae in some patients. Paired serum samples were taken 10–14 days apart to assess the serolog- ic response to coronavirus by immunofluorescence assay (IFA). All chest radiographs were classified according to their laterality and extent of involvement. Qualitative RT-PCR Testing The NPA sample collected from patients was added into a sterile vial containing 2 mL of viral transport medium and then transported on ice (4°C) to the Public Health Laboratory Centre, Government Virology Unit (GVU) of Hong Kong. Total RNA from 140 µ L of each NPA sample was extracted by a QIAamp viral RNA Mini kit (QIAGEN, Valencia, CA), as instructed by the manufacturer and elut- ed in 60 µ L of buffer. A total of 4.2 µ L of eluted RNA was reverse-transcribed with use of reverse transcriptase (Applied Biosystem, Foster City, CA) in a 20-µ L reaction containing 2.5 µ M (final concentration) of random hexam- er. The mixture was incubated at room temperature for 10 min and then at 42°C for 15 min. The reaction was stopped at 95°C for 5 min and then chilled in ice. The primers used for amplification, COR-1 and COR-2, were targeted at the coronavirus polymerase gene designed by GVU: sense 5′ CAC CGT TTC TAC AGG TTA GCT AAC GA 3′and anti- sense 5′ AAA TGT TTA CGC AGG TAA GCG TAA AA 3′, with expected product size of 311 bp. Five microliters of cDNA was amplified in 45 µ L of master mixture con- taining 5 µ L of 10X PCR buffer (Amersham Pharmacia Biotech, Piscataway, NJ), 1 µ L of 2 5 mM extra MgCl2, 4 µ L of deoxynucleoside triphosphates (dNTPs) (2.5 mM each), 0.5 µ L of each primer, 0.3 µ L of Taq polymerase (5 U/mL), and 33.7 µ L of molecular grade water. One posi- tive control and one negative control were included in each PCR assay. Reactions were performed in a thermocycler (GeneAmp PCR System 9700, Applied Biosystem) with the following conditions: at 94°C for 3 min, followed by 45 cycles of 94°C for 30 s, 60°C for 30 s, 72°C for 1 min, and 72°C for 7 min. PCR products were analyzed by gel electrophoresis. Treatment All patients received treatment according to a standard protocol. Either a β-lactam plus β-lactamase inhibitor or third-generation cephalosporin in combination with a macrolide or a fluoroquinolone was given to the patient at admission. Per the recommendation of the Hospital Authority of Hong Kong, an antiviral drug (ribavirin 24 mg/kg/day intravenously, together with hydrocortisone 10 mg/kg/day) was administered if the symptoms did not respond within 48 h (The recommendations were found available at: URL: http://www.ha.org.hk/hk/hesd/ nsapi/?Mlval=ha_view_content&c_id=122711&lang=E. However, the recommendations have since changed and are available at: URL: http://www.ha.org.hk/hesd/ nsapi/?MIval=ha_view_content&c_id=123510&hesd_lan g=E). Methylprednisolone, in the form of two to three pulsing doses of 500 mg to 1,000 mg a day intravenously, was administered to those with a persistent fever, radiolog- ic evidence progression of lung infiltrates, or signs of res- piratory distress despite the initial antiviral-hydrocortisone combination. Statistical Analysis Bivariate analysis was performed for epidemiologic, clinical, laboratory, radiologic data, and outcomes by using RT-PCR results as the dependent variable. Data of contin- uous variables were expressed as mean and standard devi- ation. Chi-square test was used for categorical variables, and the unpaired Student t test was performed for continu- ous variables. All significant factors for death with a p value <0.1 were pooled into a multivariate logistic regres- sion model with backward stepwise analysis to identify the independent predictors for the clinical outcome. A p value <0.05 (two-tailed) was assumed to be statistically signifi- cant. All analyses were performed with the SPSS version 10.0 software (SPSS Inc, Chicago, IL). Results Demographic Findings On admission, nasopharyngeal RT-PCR was performed on 90 male and 128 female patients (mean age 39.6 ± 14 years). All patients, except six, were Chinese; two were Indonesian, and four were Filipino. Twenty-one of the patients (10%) were healthcare workers, including 5 clini- cians, 9 nurses, 5 ward assistants, and 2 allied health work- ers who worked in the SARS wards. Forty-one patients 1382 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 9, No. 11, November 2003