From the Johns Hopkins University, Bloomberg School of Public Health, Baltimore, Maryland.
Correspondence: Kenrad Nelson, Johns Hopkins University, Bloomberg School of Public Health, 615 N. Wolfe Street, E7132, Baltimore, MD 21205. E-mail: firstname.lastname@example.org.
Acute diarrheal disease among children younger than 5 remains a major cause of morbidity and mortality worldwide. An Expert Committee of the World Health Organization recently estimated that diarrhea causes 18% of the 11 million deaths among children younger than the age of 5 years in the world, nearly tied with pneumonia (19%) as the leading cause of death.1
Severe infectious diarrhea in children occurs most frequently under circumstances of poor environmental sanitation and hygiene, inadequate water supplies, and poverty. This is not to say that the problem occurs only in developing countries. Childhood diarrhea in industrialized countries is prevalent (at least 1 to 3 episodes per child per year) and has large economic costs. In developed countries, childhood diarrhea has been linked with daycare attendance, lack of breast-feeding, contact with symptomatic persons in the home or elsewhere, and exposure to contaminated food and water. However, there are few comprehensive studies of the epidemiology and microbiology of diarrheal disease in industrialized countries. Such data could be a valuable contribution to the development of public health prevention programs.
In this issue, researchers from Denmark report the results of a case–control study of diarrheal disease among children younger than 5 years of age.2 Among the risk factors in this well-off population were contact with symptomatic persons (particularly in daycare centers), contact with a dog with diarrhea, hospitalization, consumption of formula milk (which was likely a surrogate for the absence of breast-feeding), socioeconomic status, and foreign travel.
Bacterial diarrhea was specifically associated with foreign travel in the past 7 days, hospitalization in the past 2 weeks, and lower socioeconomic status. Diarrhea of viral etiology was associated with contact with ill persons in the past 2 weeks, hospitalization in the past 2 weeks, or a diagnosis of asthma. The authors conclude that bacterial diarrhea is primarily acquired by food or water, whereas viral diarrhea is primarily spread by direct contact with ill persons.
In another report from this study, Rotavirus infection was the most important single cause of diarrhea for those who acquired their infection within Denmark, whereas Salmonella, Escherichia coli organisms (ETEC, EPEC, EAggEC), and Cryptosporidium were associated with diarrhea acquired during foreign travel.3
The present analysis2 focuses on the subset of children with diarrhea severe enough to visit a physician and have a culture sent to a laboratory. This emphasis provides direct guidance for public health programs needed to reduce childhood diarrhea in a developed country. A particular target should be daycare. There has been a dramatic increase in the use of daycare in recent decades in the United States and Western Europe, necessitated by the increased employment of women and the rise in single-parent households. Reliance on daycare has substantially increased the incidence of childhood diarrhea and respiratory infections. Efforts are needed to improve hygiene in daycare centers, especially private daycare, to prevent transmission of pathogens.
Furthermore, these data emphasize once again that infectious diseases do not respect national borders. Improvement of conditions in developing countries would benefit those in the industrialized world, as well. Finally, an effective Rotavirus vaccine remains an urgent public health priority to reduce the worldwide morbidity and mortality of diarrheal disease.
ABOUT THE AUTHOR
KENRAD E. NELSON is Professor of Epidemiology at Johns Hopkins University Bloomberg School of Public Health, specializing in infectious disease. His research interests are the epidemiology and prevention of HIV infections and AIDS-related opportunistic infections in the United States and Asia, hepatitis, tuberculosis, and STDs. He is author of Infectious Disease Epidemiology: Theory and Practice, published by Jones and Bartlett.
1. Bryce J, Boschi-Pinto C, Shibuya K, et al. and the WHO Child Health Epidemiology Reference Group. WHO estimates of the causes of death in children. Lancet
2. Ethelberg S, Olesen B, Neimann J, et al. Risk factors for diarrhea among children in an industrialized county. Epidemiology
3. Olesen B, Neimann J, Bottiger B, et al. Etiology of diarrhea in young children in Denmark: a case-control study. J Clin Microbiol