Carrier Prevalence, Secondary Household Transmission, and Long-Term Shedding in 2 Districts During the Escherichia coli O104:H4 Outbreak in Germany, 2011

Background. From May through July 2011, Germany experienced a large outbreak of Shiga toxin―producing Escherichia coli (STEC) O104:H4 infection. Our objective was to identify the prevalence of STEC O104:H4 carriers in households in highly affected areas, the rate of secondary household transmissions, and the duration of long-term shedding. Methods. In a cross-sectional study, we recruited case and control households to determine STEC household prevalence. We then conducted a prospective cohort study (households with >2 members and ≥1 case) to determine rates of household transmission and shedding duration. Results. For part 1, we recruited 57 case households (62 case patients and 93 household contacts) and 36 control households (89 household members). We only detected cases in previously known case households and identified 1 possible adult-to-adult household transmission. For part 2, we followed 14 households and 20 carriers. No secondary household transmission was detected in the prospective follow-up period. In 1 adult carrier, shedding lasted >7 months. However, the median estimated shedding time was 10-14 days (95% confidence interval, 0-33 days). Three carriers showed intermittent shedding. Conclusions. The prevalence of STEC O104:H4 carriers even in highly affected areas appears to be low. Despite prolonged shedding in some patients, secondary adult-to-adult household transmissions seem to be rare events in the postdiarrheal disease phase.