Epidemiology of typhoid in India

Abstract

Hospital based reports suggest a decline in blood culture-confirmed typhoid in India over the past three decades with considerable heterogeneity across risk settings. Extensive use of antibiotics early in febrile illness could decrease the identification of typhoid through blood culture and may therefore be responsible in part for this apparent decline, I measured typhoid incidence through active surveillance of a paediatric cohort in a setting where hospital laboratory reporting declined from 510 cases in 1992 to 98 in 2014 to identify if typhoid transmission persists at the community despite the apparent decline in the hospital. A closed cohort of 6760 children under 15 years of age in Vellore in South India were followed weekly for a median 2.2 years between 11 October 2016 and 15 June 2019 for febrile illness. Participating families received thermometers and fever diary cards and were contacted each day during a febrile illness to record characteristics of fever episodes including antibiotic usage and clinical diagnosis. Fever lasting 3 consecutive days was investigated by study physicians with a blood culture. The incidence of typhoid and of fever related antibiotic use were calculated and the determinants of disease and antibiotic use were examined. We identified 176 blood culture confirmed typhoid cases in 14812 child years of observation, with an incidence of 1187 cases (95% CI, 1025 – 1377) per 100,000 child-years. Correction for sensitivity of blood cultures and refusal of blood culture raised the incidence to 2092 (95% CI, 1869-2330) per 100,000 child-years. Antibiotic use for more than two days decreased the odds of culture confirmation by 46% (95% CI 9% -69%). The incidence of fever-related-antibiotic use was 44 episodes per 100 child years, much usage was inappropriate and early, with azithromycin, amoxycillin and cephalosporins commonly used. Active surveillance of a paediatric cohort demonstrated high incidence of typhoid in the community which is undetected in hospital surveillance. The high incidence warrants use of typhoid conjugate vaccines and highlights the risk posed by emerging MDR to re-emergence of typhoid as a major public health issue.