Dengue has become a 21st-century global health crisis. Here's what doctors need to know.

By Stephanie Srakocic | Fact-checked by Davi Sherman
Published March 21, 2024

Key Takeaways

  • Mosquito-transmitted dengue viruses have increased rapidly in both reach and number of infections in the past 24 years.

  • Factors such as urbanization, increased global travel, and climate change have driven this rise.

  • Vaccines are available but haven’t been produced at a high enough volume to meet needs.

In 2000, about half a million cases of dengue and 19,685 deaths were reported worldwide. By 2019, there were over 5 million cases and 30,000 deaths reported worldwide, the most ever. It’s expected that this year’s numbers will surpass the 2019 record.[]

In just the first two months of 2024, Brazil reported 1 million cases of the infection and 214 deaths. This is the fastest spread of the virus ever recorded in Brazil, where 1.6 million cases were reported in all of 2023. In Brazil and other countries in South America, the Pacific Islands, and South and Southeast Asia, dengue is a chronic and epidemic concern. As of March 2024, experts reported that dengue is present in 85% of Brazil’s municipalities, and in Brazil’s most populous city, São Paulo, an estimated 300 in every 100,000 citizens is believed to have dengue.[][]

Outside Brazil, other nations have also faced spikes in dengue in the first quarter of 2024. Peru had a state of emergency across most of the country on February 26, 2024, after total cases climbed to 31,300 in the first eight weeks of the year. Argentina has reported more than 74,000 cases since the beginning of this year, a dramatic 2,100% increase from the same period in 2023. In Sri Lanka, over 15,000 cases of dengue were reported between January and February of this year. The Vietnamese capital city of Hanoi reported 513 cases of dengue since the beginning of this year, triple the number of cases compared to the same period in 2023.[][][][]

Dengue has also emerged in new locations in recent years. For instance, in 2022, Niger reported its first-ever case of dengue. Over the last year, there have been a handful of dengue cases in the US, including the first known transmission in California.[][] 

Dengue’s increased reach

Dengue isn’t a new virus; it’s been recorded in medical literature for centuries. Until recently, this mosquito-transmitted virus had a limited range. However, changes to humans’ living environments have also affected conditions for dengue-carrying mosquitoes, contributing to further spread.[] 

Newly built urban areas in some developing countries can be ideal environments for mosquitoes; their numbers can increase quickly in areas with dense populations, hot temperatures, and poor sanitation standards. Dawn Wesson, mosquito expert and Associate Professor of Tropical Medicine at Tulane University’s School of Public Health and Tropical Medicine, says that the spread of these environments outside planned city centers is one of the largest factors contributing to the global spike in dengue. 

“Unplanned urbanization around the outskirts of large cities is often accompanied by water insecurity, which leads to people storing water for drinking, cooking, cleaning, and basic hygiene needs. Water stored in containers creates the perfect habitat for the mosquitoes [that] are the primary vector of dengue,” Wesson explains. 

According to the World Health Organization (WHO), climate change is another significant factor. Higher average temperatures have led to changes such as extended rainy seasons, increased humidity, and better conditions for mosquito breeding in some areas. Increased global travel has also exacerbated the spread of dengue in recent years, with many travelers unknowingly carrying the virus when they return home from trips to high-dengue areas.[] 

Dengue infections

Dengue infections don’t always cause symptoms: Some people carry the virus without developing symptoms. Others might develop mild symptoms that resolve in about a week.

In other instances, a dengue infection can be serious. Patients can experience severe abdominal pain and vomiting. Organ failure is possible, as is fatality. Estimates of dengue’s fatality rates around the globe vary, ranging from 1% to 14%.[] 

Battling dengue

Brazil is rushing to roll out The TAK-003 vaccine. In clinical trials, the cumulative vaccine efficacy over five years against dengue was over 84% against dengue-related hospitalizations.[] 

Additional vaccines are in development. The Brazilian Butantan Institute has developed the one-dose Butantan-Dengue Vaccine (Butantan D-V). The Butantan D-V has been through three phases of clinical trials so far; it’s shown 80% efficacy and has been proven safe for people who have never had dengue. If trials continue to be successful, the vaccine could be approved in 2025.[]

Beyond developing and rolling out vaccines, health experts in Brazil and around the globe are taking a broad approach to preventing dengue. Steps such as using traditional mosquito nets, wearing long-sleeved clothing, covering open water sources, and using bug repellant in dengue-prone areas—similar to steps taken to prevent malaria and other mosquito-carried infections—are key to public health prevention plans. 

“Water-holding containers are treated with an insecticide that kills the larval mosquitoes, but not every municipality has the resources to treat all containers.  Covering containers is also effective but often impractical. Space spraying or fumigation with insecticides to kill adult mosquitoes is also used in some areas,” Wesson says. 

Other potential steps include developing technology such as gene-edited mosquitoes and insecticide-laced mosquito nets, along with using antiviral treatments. However, Wesson notes that some of these methods can be cost-prohibitive. 

“Newer methods, such as the use of genetically modified mosquitoes or Wolbachia-infected mosquitoes, have also been utilized in some areas and [have been] shown to be effective in slowing or stopping transmission, but the expense of these technologies currently makes them out of reach for many places where dengue is endemic,” Wesson says. 

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