Because enterotoxigenic Escherichia coli (ETEC) is not identified by routine stool culture
methods, ETEC outbreaks may go unrecognized, and opportunities for treatment and
prevention may be missed. To improve recognition of adult ETEC outbreaks, we compared
them with reported outbreaks of viral gastroenteritis. During 1975–95, we identified 14 ETEC
outbreaks in the United States and 7 on cruise ships, caused by 17 different serotypes and
affecting 5683 persons. Median symptom prevalences were: diarrhoea 99%, abdominal cramps
82%, nausea 49%, fever 22%, vomiting 14%. The median incubation period was 42 h, and
for 8 of 10 outbreaks, the mean or median duration of illness was >72 h (range 24–264). For
17 (81%) ETEC outbreaks, but for only 2 (8%) viral outbreaks, the prevalence of diarrhoea
was [ges ]2·5 times the prevalence of vomiting. ETEC outbreaks may be differentiated from viral
gastroenteritis outbreaks by a diarrhoea-to-vomiting prevalence ratio of [ges ]2·5 and a longer
duration of illness.