First they visited all households in the area, numbered the houses, and listed all the family members. The survey team visited the selected census enumeration block. In India, during decennial census operations, an enumerator is allotted one census enumeration block, which has about 120–150 households. One census enumeration block was selected randomly from each cluster. Four clusters (two from urban and two from rural areas) were selected randomly from each district. We considered wards in urban areas and villages in rural areas as clusters. In each region, three states were randomly selected, and from each state, four districts were selected by probability proportional to population size. The age-stratified serosurvey covered three age groups (ie, 5–8, 9–17, and 18–45 years) across five geographical regions (north, northeast, east, south, and west) of India.
We tested the serum samples collected as part of the dengue study for CHIKV. We did a nationally representative, cross-sectional, population-based serosurvey, which estimated the seroprevalence of dengue virus infection. In this context, we tested the samples collected as part of a national serosurvey for IgG antibodies against CHIKV among individuals aged 5–45 years to estimate the age-specific seroprevalence of CHIKV infection in India. The few seroprevalence studies reported from India thus far were either done in a limited geographical area or after an outbreak. Routine surveillance data from India's National Vector-Borne Disease Control Programme and the virus research and diagnostic laboratories network suggest continued transmission of CHIKV after its re-emergence in 2005. In India, the first wave of CHIKV outbreaks was reported during 1963–73. Studies had reported seroprevalence of CHIKV ranging from 2♹% (Andaman Islands) to 68♰% (Kerala). We identified 21 publications, of which four reported seroprevalence of CHIKV infection. We searched PubMed for estimates of seroprevalence of chikungunya virus (CHIKV) infection in India from database inception until Oct 31, 2019, using the search terms “chikungunya” AND “seroprevalence” AND “India” with no language restrictions. The estimated proportion of the population susceptible to CHIKV in 2017 was lowest in the southern region (56♳%) and highest in the northeastern region (98♰%). FOI was lowest in the eastern and northeastern regions. Heterogeneous FOI models suggested that the FOI was higher during 2003–07 in the southern and western region and 2013–17 in the northern region. The seroprevalence did not differ by sex (male 18♸% vs female 17♶% p=0♵0). There was a significant difference in seroprevalence between rural (11♵% ) and urban (40♲% ) areas (p<0♰001). The seroprevalence was lowest in the northeast region (0♳% ) and highest in the southern region (43♱% ). The overall seroprevalence was 9♲% (5♴–15♱) among individuals aged 5–8 years, 14♰% (8♸–21♴) among individuals aged 9–17 years, and 21♶% (15♹–28♵) among individuals aged 18–45 years. The overall prevalence of IgG antibodies against CHIKV in the study population was 18♱% (95% CI 14♲–22♶). Of 17 930 randomly selected individuals, 12 300 individuals participated and their samples were used for estimation of CHIKV seroprevalence. The Lancet Regional Health – Western Pacificįrom June 19, 2017, to April 12, 2018, we enumerated 117 675 individuals, of whom 77 640 were in the age group of 5–45 years.The Lancet Regional Health – Southeast Asia.
The Lancet Gastroenterology & Hepatology.
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