Mosquito-transmitted disease dengue exposure may provide some degree of immunity against COVID-19, a recent research reported in Brazil that studied a coronavirus outbreak. The not yet released research, led by Duke University professor Miguel Nicolelis and shared solely with Reuters, compared the geographical distribution of cases of coronavirus with dengue spread in 2019 and 2020.

Nicolelis found that areas with lower rates of coronavirus infection and higher case development were sites that had experienced severe dengue outbreaks this year or last. The study said, relating to dengue virus antibodies and the current coronavirus, “This striking result increases the fascinating prospect of immunological cross-reactivity between dengue serotypes of Flavivirus and SARS-CoV-2.”

“This theory may mean, if proved right, that dengue exposure infection or immunisation with an efficient and healthy dengue vaccine could provide any degree of immunological defence” against coronavirus, it said. Nicolelis told Reuters the findings are especially interesting because previous experiments have shown that even though they have never been bitten by the coronavirus, people with dengue antibodies in their blood might test falsely positive for COVID-19 antibodies.

“This shows that there is an immunological association that no one should have predicted between two viruses, since the two viruses come from entirely different families,” Nicolelis said, adding that more studies are required to confirm the connexion. The paper was released on the MedRxiv preprint list ahead of peer review and will be posted to a scholarly journal.

It illustrates an important link between lower COVID-19 prevalence, mortality and growth rate in Brazilian populations where dengue antibody levels were higher. With over 4.4 million cases, Brazil has the world’s third-highest number of COVID-19 infections-trailing only the United States and India.

COVID-19 took even longer to achieve a high degree of population dissemination in states such as Paraná, Santa Catarina, Rio Grande do Sul, MatoGrosso do Sul and Minas Gerais, with a high frequency of dengue last year and early this year, relative to states such as Amapá, Maranhão and Pará that had less dengue incidents. The team observed a close link between dengue outbreaks and a slower spread of COVID-19 in other areas of Latin America, as well as in the Pacific and Indian Occ islands of Asia and India.

During a study based on how COVID-19 had spread across Brazil, Nicolelis said his team came across the dengue discovery by mistake, in which they discovered that highways played a major role in the dissemination of cases across the world. The team went in search of potential hypotheses after finding some case-free places on the map. When the researchers matched the propagation of dengue with that of the coronavirus, a breakthrough arrived.