EMERGENCE OF SARS Table 2. Quantities of SARS-CoV in sputum and stool specimens from three confirmed SARS case-patients, as measured by quantitative RT-PCR, United States, 2003a Time of specimen collection after Case-patient identification no. Specimen illness onset (no. of days) Copies per gram of sample 5 Sputum 14 43,000,000 7 Stool 14 37,000,000 Stool 18 1,600,000 Stool 21 930,000 Stool 26 2,300,000 6 Stool 19 45,000 aSARS-CoV, severe acute respiratory syndrome–associated coronavirus; RT-PCR, reverse transcriptase–polymerase chain reaction. Household Transmission Ten household contacts of five of the seven SARS case- patients were enrolled. Case-patient 1 had four household contacts, case-patients 3 and 4 had one such contact each, and case-patients 6 and 7 had two household contacts each. Of the 10 household contacts, 4 were female, 2 were smok- ers, and 2 reported previous history of respiratory problems (sarcoidosis in household contact 5 and pulmonary em- bolus in household contact 7). Household contact 1 (who was also case-patient 2) was the only such contact who tested positive for SARS-CoV antibody. The remaining nine household contacts were negative for SARS-CoV antibody in specimens collected >28 days after their initial exposure to a case-patient. The infected household contact was the wife of confirmed SARS case-patient 1. The couple had visited Hong Kong together in early March 2003 and stayed at Hotel M, which was subsequently linked to the initial spread of SARS (16), where they had multiple opportunities for exposure. Case- patient 1 became ill 7 days after returning to the United States from Hong Kong. Symptoms developed in house- hold contact 1 some 13 days after returning to the United States and 6 days after onset of illness in her husband. SARS-like symptoms did not develop in any of the three other household contacts of case-patient 1, nor did any have laboratory evidence of SARS-CoV infection. The analysis of household exposures and protective measures in this household indicated that household contact 1 had more frequent unprotected contact with the index patient compared with three other household contacts (Table 4). The remaining six uninfected household contacts reported close contact (e.g., contact within 3 feet and unprotected skin-to-skin contact) with case-patients. The exposure of four household contacts of two case-patients with stool specimens positive for SARS-CoV was limited by isolation of the case-patients in a separate room with a private bathroom during the first week of illness. Both case-patients also wore surgical masks during this period, as did three of their four household contacts. Case-patient 7 was hospitalized from day 11 to day 18 of illness, the period during which the highest amounts of virus were detected in his stool, and continued to be positive for SARS-CoV in stool after discharge. Neither case-patient 7 nor his two household contacts wore surgical masks after being discharged from the hospital. Case-patient 6, who was never hospitalized, had low-level shedding of SARS- CoV in stool on day 19, but no virus was subsequently found in his stool specimens. One of his two household contacts wore a mask until 10 days after the resolution of fever in the case-patient. Discussion In this investigation of U.S. SARS-CoV–infected per- sons and their household contacts, we identified probable transmission of SARS-CoV to only 1 of 10 such contacts. Table 3. SARS-CoV antibodies as determined by enzyme-linked immunosorbent assay in seven confirmed SARS case-patients, by number of days after illness onset, United States, 2003a Case-patient Days after illness onset SARS-CoV antibodiesb Patient 1 6 Negative 34 1,600 Patient 2 4 Negative 28 6,400 64 6,400 Patient 3 6 Negative 25 6,400 46 1,600 71 1,600 Patient 4 2 Negative 5 Negative 13 Negative 30 6,400 Patient 5 14 Negative 41 1,600 Patient 6 10 1,600 11 1,600 15 6,400 23 6,400 Patient 7 11 400 15 1,600 18 6,400 21 6,400 26 1,600 32 6,400 aSARS-CoV, severe acute respiratory syndrome–associated coronavirus. bReciprocal of dilution. 228 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 2, February 2004