During the research, 1.5 million dengue infections in 21 Asian and American countries were analyzed between 1993 and 2019. Only countries where the disease is endemic, i.e. regularly occurs, were included in the analysis. The experts also took into account the rise in temperature, the changing precipitation conditions and the shift in population density. Using statistical methods, it was determined that rising temperatures were specifically responsible for 19% of dengue infections.
Erin Mordecai, associate professor of biology at Stanford University and co-author of the study, said:
This is the first time that climate change has been linked to the spread of dengue.
The expert added that mosquitoes are cold-blooded animals, so their internal temperature changes depending on the environment. The warmer the temperature, the faster they grow and reproduce, increasing the number of individuals capable of spreading disease.
Researchers have determined that there is an optimal temperature range in which mosquitoes can transmit dengue to humans. Below 15 degrees Celsius, the virus multiplies too slowly in mosquitoes to be easily spread. However, as the temperature rises, the amount of virus in mosquitoes increases and thus results in a higher infection rate, which
it peaks at about 29 degrees Celsius.
According to forecasts, in certain areas of Peru, Mexico, Bolivia and Brazil – where dengue is already endemic – the number of infections may increase by more than 150% in the coming decades. At the same time, temperatures above 30 degrees Celsius can shorten the lifespan of mosquitoes, thus, in regions that are already very hot, such as southern Vietnam, rising temperatures may reduce infection rates somewhat.
Mordecai emphasized: “Measures to reduce carbon dioxide emissions and thereby mitigate global warming would help prevent this potential increase in global infections.” The researchers predicted that if carbon dioxide emissions were reduced to net zero around 2050 or later, the number of dengue cases would increase by 7% overall, and by as little as 30% in some countries.
Although most people diagnosed with dengue have mild symptoms or remain asymptomatic, some patients can develop serious complications.
About 1% of people treated for the infection still die from the disease, and this rate can rise to 20% without treatment.
Dengue fever is also becoming more common in the United States. In recent years, locally acquired cases have been reported from California, Texas, Florida, Hawaii, and Arizona. Mordecai warned, “Dengue is coming, and dengue will get worse in places that are currently in the temperature range for transmission.” It also affects high altitude tropical regions, southern Brazil, North America and Europe.
According to the expert, there are currently not many dengue infections in these places, thanks to the temperate climate. However, global warming may mean they need to start stepping up public health responses to reduce mosquito populations and therefore infections.
The cover image is an illustration. Cover image source: Portfolio
Source: www.portfolio.hu
