Mosquito Invasion Exposes U.S. to Dengue Fever, Study Finds

Two types of mosquitoes capable of transmitting the dengue fever virus are invading Southern and Mid-Atlantic states, creating conditions more favorable for an outbreak, according to a report released today by the Natural Resources Defense Council (NRDC).

“Areas of the United States previously inhospitable to the disease now support populations of mosquitoes capable of carrying the virus–a problem that may worsen with global warming,” NRDC said in a statement.

“An estimated 173.5 million Americans live in counties that now contain one or both of the mosquito species.”

Dengue vulnerability in the United States


Among the social and environmental factors that increase community vulnerability to dengue and other infectious diseases are poor municipal infrastructure and frequent storm damage to homes. Red areas of the map show U.S. counties that have reported the presence of one or both of the mosquito species (Aedes aegypti and Aedes albopictus) that can potentially transmit dengue fever; blue regions highlight the area encompassing most of the positive counties.

Map courtesy NRDC

“Milder winters, hotter, wetter summers and even droughts can bring this insect-borne threat closer to home,” said Kim Knowlton, NRDC senior scientist. “Usually relegated to tropical and exotic locales, dengue fever has rarely been an issue in the United States outside of the Texas-Mexico border region. But a changing climate may allow certain species of dengue-spreading-mosquitoes to flourish in nearly half of the United States.”

NRDC’s report, “Fever Pitch: Mosquito-Borne Threat Spreading in the Americas,” finds that mosquitoes capable of transmitting dengue have spread into at least 28 US states, including Texas, Florida, Arizona, and even states as far north as New York and New Hampshire.

“In the United States, the number of physician-reported cases of the disease has more than doubled in the past decade. Nearly 4,000 cases of imported and locally-transmitted dengue were reported to the Centers for Disease Control and Prevention (CDC) between 1995 and 2005, and when the Texas-Mexico border region is included, the number jumps to 10,000 during that time.

“International rates of dengue infection have increased 30-fold in the last 50 years, to an estimated 50 to 100 million infections, a half-million hospitalizations, and 22,000 deaths annually in more than 100 countries.”

“International rates of dengue infection have increased 30-fold in the last 50 years, to an estimated 50 to 100 million infections, a half-million hospitalizations, and 22,000 deaths annually in more than 100 countries. In Mexico, Central and South America more than 900,000 dengue fever cases were reported in 2007.”

Factors Contributing to Rise in Dengue

Many factors may be contributing to the rise in dengue fever, including increasing international travel and trade, densely-populated communities living in poverty in many countries including the United States, and the effects of global warming, NRDC said.

“Researchers project that because of global warming, in the next 75 years 3 billion additional people will become at risk for the disease across the globe.”

Known as “Breakbone Fever” because of its classic symptoms, dengue is characterized by agonizing aching in the bones, joints and muscles, a pounding headache, pain behind the eyes, a high fever and a classic rash.

There is no cure or vaccine against the virus, only preventative and supportive care.

Actions Can Reduce Spread

Both large-scale and individual actions can reduce the spread of dengue fever, NRDC said.

“Individuals can protect themselves and their families from mosquito-borne illnesses by wearing loose-fitting long sleeves and pants when outdoors and using DEET (not more than 30%) on exposed skin when the bugs are biting.

“Individuals can also make sure windows and doors have tight fitting screens and that they don’t leave open containers of water in or near their homes. Further precautions should also be taken while traveling to countries where dengue fever is already established.

“At a national and international level, strong climate legislation is needed to slow global warming.

“The Centers for Disease Control and Prevention (CDC) should require reporting of dengue fever so the spread of the disease within the US can be accurately tracked.”

NRDC’s report recommends that local and national governments train clinicians, share surveillance data, enhance lab capacity, and coordinate with international partners to prevent future outbreaks and reduce the threat to public health.

The National Resources Defense Council is a nonprofit environmental action group based in New York.

Changing Planet

Meet the Author
More than forty years in U.S., UK, and South African media gives David Max Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. In his 22-year career at National Geographic he was VP and editor in chief of National Geographic Digital Media, and the founding editor of the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directed the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. A regular expert on National Geographic Expeditions, David also lectures on storytelling for impact. He has 120,000 followers on social media: Facebook  Twitter  LinkedIn