Corona restrictions were not only in the way of COVID-19, but also dengue fever

In 2020, almost three quarters of a million fewer dengue virus infections occurred, which is probably (in part) due to the restrictive corona measures.

In 2020 we were all mostly confined to home. Worldwide, schools were closed and the number of trips was sharply reduced. It is possible that the restrictive corona measures have not only influenced the spread of the corona virus. Because researchers prove in a new study that in 2020 far fewer people contracted dengue fever.

Researchers studied the number of monthly dengue virus infections between 2014 and 2020 in 23 countries – sixteen in Latin America and seven in Southeast Asia. These are the main regions affected by the dengue virus.

Three quarters of a million fewer infections

It leads to a striking discovery. Because the team found a strong link between school closures, the decrease in the number of trips (because the shops were closed due to restrictive corona measures and fewer people took public transport) and a reduced risk of dengue fever. In total, almost three quarters of a million fewer dengue virus infections occurred in 2020. According to the researchers, the findings indicate that schools and high-traffic public spaces are important places for the transmission of dengue fever and play a key role in the spread of the disease.

Impact of corona measures on the spread of the dengue virus. Image: London School of Hygiene & Tropical Medicine

The results provide new insight into how the dengue virus spreads. This virus is only transmitted from mosquito to human and vice versa and cannot, for example, jump from human to human.

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However, the current study shows that avoiding crowded areas does have an effect on the transmission of the dengue virus. How about that? The mosquitoes that transmit the virus are often located in urban areas. Because we spent more time at home due to corona measures, fewer people were exposed to the mosquito and there were also fewer opportunities for infected people to pass the virus on to uninfected mosquitoes.

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According to the researchers, the study provides important clues about how we can further reduce the spread of the dengue virus and the number of infections. “Currently, efforts to combat dengue fever are focused on or around the households of people who get sick,” said study researcher Oliver Brady. “However, in order to limit the transmission of the dengue virus, we now know that in some countries we also need to focus measures on the locations infected people have recently visited.”

Unique opportunity

The pandemic and the restrictions imposed on us have provided researchers with a unique opportunity to study how human movements and behavior contribute to the transmission of dengue fever. And we can now take advantage of that. “Despite all the damage the pandemic has caused, it has also given us the opportunity to devise new interventions and targeted strategies to prevent dengue fever,” said Brady.

Immunity

The researchers are closely monitoring further developments. Unraveling the consequences of corona restrictions on the number of dengue virus infections is very complex. 2019 saw the largest global dengue outbreak in history, with more than 5.2 million cases in the Americas and Southeast Asia. According to the researchers, this has led to a high level of immunity that is also expected to have an impact on the low number of dengue virus infections in 2020.

Incidentally, according to the researchers, it remains to be seen to what extent the estimated 0.72 million dengue virus infections have actually been averted, or have simply been postponed until later, as the world is slowly but surely getting back on track and more and more corona measures are being banned. It is therefore crucial, according to the research team, to continue to closely monitor developments in 2022 and in the years beyond.