Few studies provide data on the global morbidity and mortality caused by infection with Shigella spp.; such estimates are needed, however, to plan strategies of prevention and treatment. Here we report the results of a review of the literature published between 1966 and 1997 on Shigella infection. The data obtained permit calculation of the number of cases of Shigella infection and the associated mortality occurring worldwide each year, by age, and (as a proxy for disease severity) by clinical category, i.e. mild cases remaining at home, moderate cases requiring outpatient care, and severe cases demanding hospitalization. A sensitivity analysis was performed to estimate the high and low range of morbid and fatal cases in each category. Finally, the frequency distribution of Shigella infection, by serogroup and serotype and by region of the world, was determined. The annual number of Shigella episodes throughout the world was estimated to be 164.7 million, of which 163.2 million were in developing countries (with 1.1 million deaths) and 1.5 million in industrialized countries. A total of 69% of all episodes and 61% of all deaths attributable to shigellosis involved children under 5 years of age. The median percentages of isolates of S. flexneri, S. sonnei, S. boydii, and S. dysenteriae were, respectively, 60%, 15%, 6%, and 6% (30% of S. dysenteriae cases were type 1) in developing countries; and 16%, 77%, 2%, and 1% in industrialized countries. In developing countries, the predominant serotype of S. flexneri is 2a, followed by 1b, 3a, 4a, and 6. In industrialized countries, most isolates are S. flexneri 2a or other unspecified type 2 strains. Shigellosis, which continues to have an important global impact, cannot be adequately controlled with the existing prevention and treatment measures. Innovative strategies, including development of vaccines against the most common serotypes, could provide substantial benefits.
PIP: This article presents a review of the literature published between 1966 and 1997 on Shigella infection. The purpose of the review is to provide data on the global morbidity and mortality caused by the infection and to plan strategies of prevention and treatment. The data obtained from this literature were used to calculate the number of Shigella infection cases and the associated mortality occurring worldwide each year, by age and by clinical category. The burden of Shigella infection was also estimated by serogroup and serotype. A sensitivity analysis was performed to estimate the high and the low range of morbid and fatal cases in each category (mild cases remaining at home, moderate cases requiring outpatient care and severe cases demanding hospitalization). The result of the calculations and analysis revealed that the annual number of Shigella infections throughout the world was estimated to be 164.7 million. 163.2 million occurred in developing countries, with 1.1 million deaths, and 1.5 million occurred in industrialized countries. More than half of the episodes and death affects children under 5 years of age. In comparing developing countries against industrialized countries, the median of isolates are S. flexneri (60% vs. 16%), S. sonnei (15% vs. 77%), S. dysenteriae (6% vs. 1%), and S. boydii (6% vs. 2%). The predominant serotype of S. flexneri in developing countries is 2a, followed by 1b, 3a, 4a, and 6, while in industrialized countries most isolates are S. flexneri 2a and unspecified type 2 strains.