The Increasing Burden of Dengue Fever in a Changing Climate - The Rockefeller Foundation

When most people think of climate change, they envision melting icebergs and a rising sea level. While climate change is indeed warming the globe and causing the seas to rise, that is not the only detrimental effect. Disruption of weather patterns can include stronger and more frequent storms, droughts, wildfires, extreme flooding and heat waves. Climate change can also affect agriculture and land use. As regions become less livable, more people will become climate refugees. Warming temperatures and unprecedented flooding have also encouraged the spread of mosquitos well beyond their traditional breeding grounds, bringing dengue fever, malaria and the Zika virus to areas never before threatened by these debilitating illnesses. If nothing is done, Zika will threaten an additional 1.3 billion people by 2050, and dengue fever will impact 60 percent of the world's population by 2080.

But many climate impacts on health are already happening. In the last fifty years, the incidence of dengue fever has increased 30-fold by one estimate, to an annual rate of 390 million infections worldwide, 96 million of which are symptomatic cases. An estimated 3.9 billion people, in 129 countries, are at risk of infection. This is not a problem of the future. It's an expanding threat that needs to be addressed today.

The virus

The virus that causes dengue is a member of the genus Flavivirus, which also includes yellow fever virus, West Nile virus, and Zika virus. Dengue virus exists as four distinct serotypes (closely related forms of the virus). Immunity from infection with one serotype may provide lifelong protection from that serotype, but is only partially protective against other serotypes.

The disease

Infection with the dengue virus can result in a wide spectrum of disease severity. Approximately 75% of infections cause little or no clinical disease, but some may produce flu-like symptoms such as high fever, headache, and painful body aches that have earned it the nickname of "breakbone fever." Patients usually recover in a few weeks with supportive care, including rest, hydration, and pain killers.

In 1-5% of cases, severe dengue can develop, as dengue hemorrhagic fever or dengue shock syndrome. The severe bleeding, shock, and organ failure can be fatal in up to 20% of severe cases, but treatment (supportive care, intravenous fluids and electrolytes, blood transfusions), can reduce mortality in severe cases to less than 1%. A second infection with a different serotype than the first infection increases the risk of severe dengue.

A vaccine to prevent dengue fever has been approved in twenty countries. It should only be used in individuals who have previously been infected with the dengue virus. Those who receive the vaccine without a previous history of infection are at a higher risk of severe dengue. Recently, however, a new vaccine was approved for use in Indonesia that does not require a previous infection. That vaccine has also been recommended by the European Medicines Agency, a step toward approval for use in the EU.

The vector

The dengue virus cannot normally be transmitted from person to person directly, except in rare instances, such as through a blood transfusion or to a fetus during pregnancy. Transmission usually occurs through a mosquito vector. Mosquitoes are infected when they bite an infected person. The virus replicates in the infected mosquito, which can then transmit the virus to another person in a subsequent blood meal.