Initial data from Phase I of an epidemiological study on dengue fever in Kerala, launched by the Department of Community Medicine, Government Medical College, Thiruvananthapuram (GMCT), in partnership with the World Health Organization (WHO), have reported a dengue seroprevalence (level of a pathogen in a population, as measured in blood serum) rate close to 42% in children between 9-12 years in the district.
The seroprevalence among 5- to 8-year-olds in a group from SAT Hospital was found to be 27%.
This is the first scientific study to be launched in Kerala, exploring the epidemiology of dengue in the State, so that evidence-based strategies can be developed to tackle future outbreaks.
The data were presented before a visiting WHO team from Geneva here on Thursday for further deliberations.
Dengue seroprevalence (detection of dengue-specific immunoglobulin G or IgG antibodies in blood samples) indicates the rate of previous dengue exposure and is an indicator of the intensity of dengue transmission in a community/locality.
“We expect the seroprevalence in adults to be much higher. The fact that 42% of children are already infected by dengue virus by the time they are nine years of age is a matter of concern because these children would be at a higher risk during another dengue epidemic when a different serotype of the virus may be in circulation. Already, three dengue virus types (DEN 1, 2 and 4) are endemic in Thiruvananthapuram while all four types are circulating in Kerala,” says Indu P.S., Professor and Head, Community Medicine Department.
In certain high dengue burden clusters — Nemom and Vilavoorkal — the seroprevalence among children was as high as 60%. Even in the so-called low-burden clusters such as Karakulam, the seroprevalence rate was 32%.
“More worrying is the fact that most of these children/families were unaware that they had already contracted dengue because they must have had sub-clinical infections. They could miss the implication of a second dengue infection. Globally too, 80% of dengue cases are asymptomatic,” Dr. Indu says.
The study, launched in 2017 November, is expected to be carried out in two more districts, Kollam and Kozhikode.
Phase I of the study involved school-based surveillance studies among 9-12-year-olds. In Thiruvananthapuram, 1,400-odd children were studied.
In Phase II, which is to be launched soon, a cohort of 500 dengue patients (who have been found to be positive through PCR test) will be followed up for a period to study the clinical, biochemical, immunological, and virological determinants or predictors of future dengue infections.
The Directorate of Health Services, the Departments of Microbiology and Paediatrics, GMCT; Rajiv Gandhi Centre for Biotechnology, State Public Health Lab, and ICMR’s Vector Control Research Centre are the technical collaborators.