Asymptomatic seroconversion in healthy people against dengue and chikungunya in Kandy district of Sri Lanka

Abstract

AbstractBackgroundBoth dengue and chikungunya are transmitted byAedes aegyptiand have many similarities in epidemiology and clinical manifestations. These two viruses are known to cause asymptomatic infection, however, studies to assess the seroprevalence in healthy individuals are limited. Our objective is to estimate the asymptomatic seroconversion status of both these infections Sri Lanka where dengue has been endemic and the last notable outbreak of chikungunya occurred in 2007.MethodsThe study was performed using venous blood samples of 454 healthy individuals (age range 11-78) in Kandy district, who had no known history of dengue or chikungunya infections in the past or present. Samples were tested for dengue NS1 antigen, dengue IgM, dengue IgG, Chikungunya IgM and Chikungunya IgG by using commercially available ELISA kits. Statistical data analysis was performed using SPSS software version 16.0 (SPSS, Inc., Chicago, IL, USA).Pvalue <0.05 was considered statistically significant.ResultsOf the 454 healthy individuals, 287 (63.2%) were positive for dengue IgG indicating a past infection and 18 (4%) were positive for dengue-specific IgM. Of the same total, 82 (18.1%) were positive chikungunya chikungunya-specific IgM and only 6 (1.3%) were positive for chikungunya-specific IgM. The number of individuals positive for both dengue IgG and Chikungunya IgG, indicating dual antibody prevalence or exposure to both diseases asymptomatically was 61(13.43%). For dengue specific IgG, the highest sero-conversion rate (80.4%) was observed in 51-60 year age group whilst the lowest (50%) in the age group 11-20. Out of the MOH areas, the highest prevalence (71.4%) of positives were observed in Bambaradeniya and the lowest prevalence (53.1%) in Yatinuwara suburbs in Kandy. The highest percentage of dengue IgM prevalence (6.3%) was observed in the age group 21-30 years and the lowest percentage (1.5%) was observed in the age group 11-20.ConclusionsAn asymptomatic seroconversion rate was observed in both dengue and Chikungunya infections. Dengue records a high rate due to its endemicity and periodic outbreaks. It is interesting to note the low-grade prevalence of Chikungunya infection contrary to the belief itsnon-existence in the island currently.