SYNOPSISObjectives. To identify cases and determine risk factors for an outbreak of Escherichia coli (E. coli) O157:nonmotile (NM) infections in children attending a summer day care program in California.Methods. The authors conducted a retrospective cohort study; the cohort comprised first and second graders who attended the day care program during the last week in August 1999. Shiga toxin testing and molecular subtyping using pulsed-field gel electrophoresis were performed on isolates. Lake water, lake bottom sediment samples, and waterfowl feces from the lake environs were cultured for E. coli O157.Results. Three cases of Shiga toxin-producing E. coli O157:NM infections with matching pulsed-field gel electrophoresis patterns and four probable cases were found. Children who swallowed more than a mouthful of water had a higher attack rate than those who swallowed less than a mouthful or none at all (43% vs. 10%, relative risk = 4.43, 95% confidence interval 1.12, 17.50).Conclusions. E. coli O157:NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.

E. coli O157: NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.

The marked decline in infectious-disease-associated mortality that took place in the United States during the first half of the 20th century contributed to the sharp drop in infant and child mortality and the more than thirty-year average increase in life expectancy over the past 100 years. The 19th-century discovery that microorganisms are the cause of many diseases led to substantial improvements in sanitation and hygiene, formulations of vaccinations, development of diagnostic tests, and the introduction of antibiotics. Despite this overall progress, devastating pandemics of infectious diseases occurred during the 20th century including the influenza in 1918 and human immunodeficiency virus first recognized in 1981. This chapter reviews major 20th-century achievements in the control of infectious diseases in the United States and ends with a discussion of challenges for the 21st century.