Enterohemorrhagic Escherichia coli outbreaks related to childcare facilities in Japan, 2010-2013

Abstract

Background: Enterohemorrhagic Escherichia coli (EHEC) is an important cause of gastroenteritis in Japan. Although non-O157 EHEC infections have been increasingly reported worldwide, their impact on children has not been well described. Methods: We collected national surveillance data of EHEC infections reported between 2010 and 2013 in Japan and characterized outbreaks that occurred in childcare facilities. Per Japanese outbreak investigation protocol, faecal samples from contacts of EHEC cases were collected regardless of symptomatic status. Cases and outbreaks were described by demographics, dates of diagnosis and onset, clinical manifestations, laboratory data, and relation to specific outbreaks in childcare facilities. Results: During 2010-2013, a total of 68 EHEC outbreaks comprised of 1035 cases were related to childcare facilities. Among the 66 outbreaks caused by a single serogroup, 29 were serogroup O26 and 22 were O157; 35 outbreaks were caused by stx1-producing strains. Since 2010, the number of reported outbreaks steadily increased, with a rise in cases and outbreaks caused by stx1-producing O26. Of 7069 EHEC cases reported nationally in 2010-2011, the majority were caused by O157 (n = 4938), relative to O26 (n = 1353) and O111 (n = 195). However, relative to 69 cases of O157 (2%) associated with childcare facility EHEC outbreaks, there were 131 (10%) such cases of O26, and this trend intensified in 2012-2013 (O157, 3%; O26, 24%; O111, 48%). Among family members of childcare facility cases, the proportion of cases that were symptomatic declined with age; 10/16 cases (63%) aged 6years or younger, 16/53 cases (30%) 6-19 years old, 23/120 cases (19%) 20-49 years old and 2/28 cases (7%) 50years or older were symptomatic. Thirty one of the 68 outbreaks (46%) were classified as foodborne-related. Conclusions: Childcare facility EHEC outbreaks due to non-O157 serogroups, particularly O26 and O111, increased during 2010-2013. These facilities should pay extra attention to health conditions in children. As older family members of childcare facility cases appear to be less symptomatic, they should be vigilant about hand-washing to prevent further transmission.