EMERGENCE OF SARS 19 (18%), including 1 confirmed SARS case-patient, declined participation; and 77 (75%) were excluded for various reasons (negative for SARS-CoV antibody at ≥21 days after illness onset, a confirmed alternative diagnosis, or foreign citizen not residing in the United States). The household contacts of seven laboratory-confirmed case- patients were also enrolled. Household contacts were defined as persons who had lived in the same household with SARS case-patients during their illness. All partici- pants provided informed consent. Timeline for Follow-up Visits Follow-up visits were scheduled twice a week for the first 3 weeks after illness onset and then once a week for 2 weeks. If a case-patient was first enrolled after week 5 of illness, then a follow-up visit was made as soon as feasible after enrollment. Some case-patients were enrolled at >5 weeks after illness onset and, therefore, were followed up for >10 weeks. For household contacts, visits were sched- uled once weekly for a period of 4 weeks after initial expo- sure to the case-patient. A single follow-up visit was scheduled if the household contact was enrolled >4 weeks after initial exposure to the case-patient. Clinical and Epidemiologic Data At the initial visit with the SARS case-patients, we col- lected data on demographics, date of illness onset, clinical symptoms, and exposure history. At the initial visit with household contacts, we gathered data on any illness they had had since their exposure to the case-patient and on the types and patterns of exposure (e.g., sleeping in the same room at night, daily contact within <3 feet, and direct skin- to-skin contact, such as kissing or hugging, with case- patients). At each subsequent visit, we collected informa- tion on any symptoms experienced by case-patients or household contacts since their previous visit, including symptoms during the current visit. Clinical Specimens Specimens collected as a part of the diagnostic work-up were available for this investigation, and at each posten- rollment visit, participants were asked to provide whole- blood, serum, stool, urine, nasopharyngeal, and oropharyn- geal swab specimens. We obtained 1–10 mL of blood from adults and 0.5–5 mL of blood from children <3 years old by venipuncture or finger stick. Clotted blood was cen- trifuged, and serum was separated before being shipped to CDC for testing. Similar volumes of whole blood were collected in a tube containing EDTA. Nasopharyngeal and oropharyngeal samples were collected by use of a single Dacron swab with a nonwooden shaft; the swab was then placed in a sterile vial containing 2 mL of viral transport medium. Stool specimens were collected in a sterile con- tainer and sealed. Participants provided a 50-mL clean- catch collection of urine in a sterile urine cup. Specimens were processed and stored according to CDC laboratory biosafety guidelines (15). All specimens were stored at 4°C for a maximum of 72 h and shipped on ice to the CDC laboratory. If shipping within 72 h was not feasible, speci- mens were stored at –70°C and then shipped. Laboratory Methods To detect SARS-CoV in stool, urine, and respiratory specimens, we performed reverse transcriptase–poly- merase chain reaction (RT-PCR), using primers targeted to the polymerase and nucleocapsid genes of the SARS-CoV genome, as described elsewhere (2, Emery et al., unpub data). Stool samples were prepared as 10% extracts in Tris- HCl buffer before isolation of total nucleic acid for RT- PCR testing. To quantify the virus load in respiratory and stool specimens, quantitative RT-PCR was performed using the TaqMan assay and standard curves generated from synthetic RNA transcripts (S. S. Monroe and R. S. Beard, unpub. data). Previously described culture tech- niques (2) were used to isolate SARS-CoV from speci- mens. To determine the S and N gene sequences of SARS- CoV, a set of 10 overlapping RT-PCR products, which cover the entire open reading frames of the S (8 products) and N (2 products) genes, were generated by using the SuperScript One-Step RT-PCR with Platinum Taq (Invitrogen, Carlsbad, CA) and sequenced by using 16 (S gene) or 7 (N gene) sequencing primers (S. Tong et al, unpub. data). Serum specimens were tested for SARS- CoV–associated antibodies by use of an enzyme-linked immunosorbent assay and an indirect fluorescent antibody test, using previously described methods (2). Serum spec- imens were considered positive only if results for both tests were positive using predetermined cut-offs (2). Results Follow-up Findings Five of seven enrolled case-patients provided data on residual symptoms. Three case-patients reported shortness of breath that persisted at least until days 50, 56, and 62, respectively, after onset of fever. Two case-patients report- ed residual coughing: case-patient 4 reported a dry cough until day 50 and case-patient 2 reported a productive cough until day 56 after onset of fever. These symptoms had been reported during the acute phase of each case-patient’s ill- ness. Wheezing developed in one case-patient without a previous history of respiratory disease at day 11 of illness and persisted at least until day 46. No data were available to characterize the progression of symptoms over time. Of 41 respiratory specimens obtained from seven case- patients (Table 1), 4 (10%) were sputum samples from two 226 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 2, February 2004