RESEARCH SARS TRANSMISSION Table 4. Profile and exposure of 10 household contacts (HHCs) of five confirmed SARS case-patients, United States, 2003 Exposure to the case-patient before Protective measures by hospitalization HHC Use of surgical mask by case- patient No Shedding SARS- HHC Case-patient documented CoV relation Age HHC identification in case- infection to case- (y)/sex/ no. no. (n=5) patient in HHC patient race 1b 1 No Yes Spouse 37/F/A 2 No Brother 57/M/A 3 No Birno-tlhawer- 55/M/A 4 No Nephew 16/M/A 5 3 No No No Spouse 52/M/W 6 4 No No No Mother 52/F/W 7 6d Yes Yes No Spouse 47/F/W 8 No Son 12/M/W 9 7f Yes Yes No Son 22/M/A 10 No Daughter 15/F/A aSARS, severe acute respiratory syndrome; F, female; M, male; A, Asian; W, white. bSARS coronavirus antibody–positive HHC. cNo soap used for handwashing (water only). dShedding documented in stool on day 19 after onset of illness. eCase-patient 6 was never hospitalized. fShedding documented in stool on days 14, 18, 21, and 26 after onset of illness. We detected SARS-CoV in fecal and respiratory speci- mens and found that SARS case-patients may have high concentrations of virus in stools during the 2nd week of ill- ness and continue to shed the virus in feces until at least 26 days after onset of symptoms. The amount of SARS-CoV in stool from a case-patient with moderate diarrhea was similarly high to the quantity seen in a sputum specimen collected from a different case-patient at the same interval after illness onset. However, no virus could be cultured from any stool specimens that were PCR-positive for SARS-CoV, suggesting that SARS-CoV in feces may be present in the form of either nonviable viral particles or antibody-coated virus. The one household contact who became infected was the person who had more contact with the potential source case-patient during the first week of illness than did other members in the household. This contact was also exposed in Hong Kong along with her husband; however, she became ill >10 days after returning to the United States (16). Previously reported data suggest that the incubation period for SARS ranges from 2 to 10 days (4,17), but in some cases, the incubation period may be as long as 14 days (18). Therefore, the possibility remains that this contact may have been infected in Hong Kong. The remaining uninfected household contacts included four contacts of two case-patients with positive stool specimens in whose households simple infection-control procedures were implemented during the acute phase of illness in the index patient. The lack of widespread household transmission of SARS found in our investigation is similar to findings in reports of the outbreak in Toronto, where 2 (6%) of 33 No. of days in house with case- patient 4 4 4 4 6 4 Alle Alle 11 11 No. of nights in same room 5–6 0 0 0 7 0 0 0 0 0 Contact within 3 Skin-to- feet skin contact (h/day) (times/day) 0–1 >3 1–3 0 0–1 0–1 >7 >7 0–1 1–3 0–1 0–1 0 0 >3 >3 1–2 1–2 1–2 0 Surgical mask used during 1st week of illness No No No No No No Yes No Yes Yes Routine handwashing with soap Noc Noc Yes Yes Yes Yes Yes Yes Yes Yes household contacts were infected despite unprotected con- tact with a SARS case-patient (19), and from the Philippines, where <1% of nonhospital contacts were reported to be infected (20). This finding supports the idea that in certain circumstances, SARS-CoV is not easily transmitted. Transmission may also be more likely to occur at the time when patients are shedding higher amounts of virus, and this period may coincide with their hospitaliza- tion, thus decreasing the degree of exposure for household contacts. We were unable to detect SARS-CoV in specimens of our case-patients before day 14 after illness onset. We only detected virus in three case-patients: in a sputum sample of one patient at day 14 and in stool samples of two patients at day >14. All upper respiratory specimens in the first 2 weeks after onset were negative for SARS-CoV by RT- PCR; this finding differs from a report in Hong Kong, where viral RNA was detected in nasopharyngeal aspirates of 68% of case-patients at day 14 (21). Our inability to detect the virus in early respiratory samples may be asso- ciated with the type (nasopharyngeal and oropharyngeal swabs versus nasopharyngeal aspirates) of collected spec- imens, as well as with low amounts of virus generally seen in such specimens (1). Sputum samples may have a higher concentration of virus than upper respiratory specimens (1), consistent with our findings. Stool specimens have been found positive more frequently than upper respirato- ry specimens during the 2nd and 3rd week of illness, which is in accord with the limited results of this study. The inability to detect SARS-CoV in urine may be the result of a late collection of urine specimens (>14 days after illness onset). A wider use of steroids in treatment of Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 10, No. 2, February 2004 229