Endemic Dengue May Have Reduced Severity of Early COVID-19 Wave in India: Study

Could the dengue virus have played a role in reducing the severity of COVID-19 during the early stages of the pandemic in India? This question arises from research conducted by the CSIR-Indian Institute of Chemical Biology in Kolkata. Their study suggests that antibodies from people who had dengue might have helped neutralize the coronavirus, leading to fewer severe COVID-19 cases and deaths in India compared to Europe or North America, where dengue is not common.

The researchers tested antibodies from dengue-infected individuals against a type of coronavirus known as murine hepatitis virus, which is similar to the human coronaviruses that caused COVID-19. Their findings, published in the Journal of Medical Virology, indicate that dengue antibodies could neutralize the coronavirus. They used computer models and cell-culture studies to show how dengue antibodies could bind to and neutralize coronavirus proteins.

However, this protective effect was not observed for all coronavirus variants.

This study builds on previous work from 2020, which found that blood tests for dengue sometimes showed positive results for SARS-CoV-2, the virus responsible for COVID-19.

Dr. Subhajit Biswas, the principal scientist and main author of the study, explained to The Hindu, “We demonstrated that serum samples from dengue patients could bind to and mask the surface of several coronaviruses, including SARS-CoV-2. Our virus neutralization tests in cell cultures showed that dengue antibodies could block coronavirus entry into cells.”

Dengue and coronavirus are different virus families, so infection with one does not typically protect against the other. Dengue has four main strains, with Denv-1 and Denv-2 being the most common in India. Infection with one strain does not protect against the others and can even lead to more severe illness if re-infected with a different strain, a phenomenon known as antibody-dependent enhancement (ADE). The researchers suggest that the prevalence of dengue in Southeast Asia might be influencing new mutations in the coronavirus, which needs further investigation.

Interestingly, the early stages of the COVID-19 pandemic saw a significant decline in dengue cases in India. The National Vector Borne Disease Control Programme reported a 75% drop in dengue cases in 2020 compared to 2019. Possible reasons for this decline include lower transmission of the dengue vector, reduced exposure due to COVID-19 lockdowns, and potential underreporting of dengue cases as attention focused on COVID-19.

Dr. Biswas added, “Our study provides evidence that pre-existing dengue immunity might have played a role in reducing COVID-19 severity and mortality in dengue-prone regions like Southeast Asia, compared to regions where dengue is rare, like Europe and North America. This might explain why severe acute respiratory infections caused by coronaviruses have been less common in India, where dengue is highly endemic.”

The researchers also considered whether cross-reactive antibodies could provide partial protection against severe dengue or increase its severity due to ADE. They hypothesize that antibodies to SARS-CoV-2 might reduce the severity of dengue. Larger clinical studies or population data from dengue-endemic regions could help understand the potential cross-protective association between these two viruses.