Attrition in serum anti-DENV antibodies correlates with high anti-SARS-CoV-2 IgG levels and low DENV positivity in mosquito vectors-Findings from a state-wide cluster-randomized community-based study in Tamil Nadu, India

Abstract

The decline in dengue incidence and/or prevalence during the COVID-19 pandemic (2020-22) appears to be attributed to reduced treatment-seeking rates, under-reporting, misdiagnosis, disrupted health services and reduced exposure to mosquito vectors due to prevailing lockdowns. There is limited scientific data on dengue virus (DENV) disease during the COVID-19 pandemic. Here, we conducted a community-based, cross-sectional, cluster-randomized survey to assess anti-DENV and anti-SARS-CoV-2 seroprevalence, and also estimated the spatial distribution of DENV-positive aedine mosquito vectors during the COVID-19 pandemic across all the 38 districts of Tamil Nadu, India. Using real-time PCR, the prevalence of DENV in mosquito pools during 2021 was analyzed and compared with the previous and following years of vector surveillance, and correlated with anti-DENV IgM and IgG levels in the population. Results implicate that both anti-DENV IgM and IgG seroprevalence and DENV positivity in mosquito pools were reduced across all the districts. A total of 13464 mosquito pools and 5577 human serum samples from 186 clusters were collected. Of these, 3.76% of the mosquito pools were positive for DENV. In the human sera, 4.12% were positive for anti-DENV IgM and 6.4% for anti-DENV IgG. While the anti-SARS-CoV-2 levels significantly correlated with overall DENV seropositivity, COVID-19 vaccination status significantly correlated with anti-DENV IgM levels. The study indicates a profound impact of anti-SARS-CoV-2 levels on DENV-positive mosquito pools and seropositivity. Continuous monitoring of anti-DENV antibody levels, especially with the evolving variants of SARS-CoV-2 and the surge in COVID-19 cases will shed light on the distribution, transmission and therapeutic attributes of DENV infection.

Fig 1

A) Spatial distribution of DENV-positive mosquito pools in Tamil Nadu B) Mosquito pools tested DENV positive by year C) Spatial distribution of seroprevalence of anti-DENV D) Number of seropositivities for anti-DENV IgM and IgG E) Distribution of DENV-seropositivity by districts F-G) Distribution of DENV-seropositivity across different age groups H) Estimation of the force of infection (FOI) of DENV. The country/region border shape was hand-drawn based on the base map layer as a template available for free from the Survey of India, Ministry of Science and Technology, Government of India (https://onlinemaps.surveyofindia.gov.in/Home.aspx).

Fig 2

Correlation between a cluster of DENV-positive mosquito pools with A) DENV-IgM seropositivity B) DENV-IgG seropositivity C) Total DENV-seropositivity—Correlation between total anti-DENV IgM positive cases with: D) Number of clusters of DENV-infested mosquito pools, E) Number of individuals seropositive for DENV, and F) Force of infection of DENV G) Simple binary regression model assessing the relationship between total population, population density and mosquito clusters positive for DENV with total (IgG and IgM) seropositivity and anti-DENV IgM positive cases.

Fig 3

A) District-wise distribution of anti-SARS-CoV-2 seropositivity in Tamil Nadu B) Average levels of anti-SARS-CoV-2 IgG titer C) Binary regression model assessing the factors associated with the anti-DENV IgM and IgG seropositivity D) Linear regression model assessing the factors associated with the level of anti-DENV IgM and IgG. The country/region border shape was hand-drawn based on the base map layer as a template available for free from the Survey of India, Ministry of Science and Technology, Government of India (https://onlinemaps.surveyofindia.gov.in/Home.aspx).