Dengue fever was found to have some level of immunity against COVID-19, a new study suggests.

Reuters first reported on the study that analyzed the coronavirus outbreak in Brazil. The link of immunity against COVID-19 and dengue fever was made by looking at past exposures.

The researchers looked at past dengue fever outbreaks and found exposure to it can give some immunity against COVID-19.

Lead author Miguel Nicolelis is a professor at Duke School of Medicine noted Daily Mail. He shared some parts of the unpublished study.

He said the study studied the distribution of coronavirus cases based on location. They linked that data with the spread of dengue for 2019 and 2020.

They found out the areas with lower infection rates of COVID-19 were places that suffered intense dengue outbreaks before. This is also true for areas with slower case growths.

As written in the study, the "striking finding" raises the possibility that there is an "immunological cross-reactivity" between the two illness' antibodies.

The study's hypothesis, if proven correct, could lead to work on a treatment that is related to dengue. An effective and safe dengue vaccine might give some level of immunity against COVID-19.

Dengue Fever Antibodies Cause False Positives

For Nicolelis, the results of their study were quite interesting.

Previous studies have shown that people who show dengue antibodies in their blood can test positive of COVID-19 antibodies. But these are only false positives.

They can still test positive of the virus despite not being infected by it at all.

Nicolelis said these false positives could mean "there is an immunological interaction between two viruses."

He added that the viruses cause the two illnesses are from two completely different families. This is also why the results are shocking.

He stressed that there are still further studies needed to prove this connection between dengue fever and COVID-19.

The study was being published on MedRxiv server but not yet been peer-reviewed. It will also be submitted to a scientific journal.

It highlighted the link between lower incidence, mortality, and growth rate of COVID-19 in locations in Brazil where levels of dengue fever antibodies were higher.

Brazil has the third-highest record of COVID-19 infections with more than 4.4 million cases. It is behind the U.S. and India.

There was a high level of dengue incidence last year and early this year in some areas of Brazil.

It took much longer for these areas to reach high community transmission of COVID-19. This is compared to places like Amapá, Maranhão, and Pará that had fewer dengue cases.

Other Parts of Latin America Show Same Results

The researchers also found the same kind of link between dengue outbreaks and COVID-19 in other parts of Latin America. They also saw this in areas in Asia, islands in the Pacific and Indian Oceans.

Nicolelis said their team's discovery on dengue came by accident. During the study, they were only focused on how COVID-19 spread in Brazil. Then, they found that highways played a major role in the spread of cases across the country.

They started drawing up a possible explanation, and the breakthrough came when the team compared dengue and COVID-19 spread.

"It was a shock. It was a total accident," Nicolelis said. "In science, that happens, you're shooting at one thing, and you hit a target that you never imagined you would hit."

As per the World Health Organization, there are about 390 million people hit by dengue fever every year. The disease is considered "endemic" to nearly 100 countries.

The largest number of dengue cases was recorded in 2019.

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