Salmonella Paratyphi A Rates, Asia

Abstract

Little is known about the causes of enteric fever in Asia.Most cases are believed to be caused by Salmonella enterica serovar Typhi and the remainder by S. Paratyphi A. We compared their incidences by using standardized methods from population-based studies in China, Indonesia, India, and Pakistan.E nteric fever still causes substantial illness and death in many parts of the world, especially in poorer nations.Salmonella enterica serovar Typhi is believed to cause most enteric fever episodes, and a smaller portion are caused by S. Paratyphi (1-3).This assumption, however, may no longer be true.Since 1999, more S. Paratyphi A than S. Typhi strains have been isolated in the province of Guangxi, southeastern China (4).Increasing isolation rates of S. Paratyphi A has also been reported from India (5).This finding has 2 major implications for the prevention of enteric fever.First, licensed typhoid fever vaccines (Vi polysaccharide and live oral Ty21a) do not protect against infections caused by S. Paratyphi A, and they may become less useful in controlling enteric fever in regions of Asia.Second, transmission and risk factors for S. Typhi and S. Paratyphi are different in Indonesia (6), so reduction strategies effective against S. Typhi may not protect against S. Paratyphi.Since little is known about the current cause of enteric fever in Asia, we compared S. Typhi and S. Paratyphi A incidence from study sites in China, Indonesia, India, and Pakistan by using standardized epidemiologic and laboratory methods (7).