'Tropical' Disease Dengue Could Impact United States

Dengue, a disease previously found mostly in the tropics and subtropics, could become a growing threat to the United States, medical experts worry.

Many scientists are putting the blame on climate change. As average temperatures around the world continue to rise, diseases once limited by cool nighttime and winter temperatures will be able to spread into new, warmer territories. That's especially the case with so-called vector-borne diseases, which are spread by pests like mosquitoes.

Dengue (pronounced "DENG-gee") is caused by four similar viruses spread by two types of mosquitoes. One of the mosquitoes, Aedes albopictus (the "Asian tiger mosquito"), has already been found in 36 states across the U.S., while the other, Aedes aegypti (the "yellow fever mosquito"), has been identified in several parts of the South.

While many people infected with dengue suffer only a mild fever, or no symptoms at all, others can develop more serious complications. These can include minor nosebleeds, high fever, severe headaches or even a leaking of blood plasma into the tissues, which can cause a dangerous drop in blood pressure. Worldwide, between 50 million and 100 million people contract dengue each year, and about 22,000 people die from the disease.

In a commentary in this month's double issue of the Journal of the American Medical Association, two physicians pointed to the need for more research to better understand and treat dengue.

Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), and David M. Morens, Fauci's senior scientific adviser, warn that past efforts to control dengue-carrying mosquitoes haven't been as effective as hoped. They add that dengue, while not yet a serious problem in the U.S., tends to spread quickly in explosive epidemics.

Dengue has already become more common in areas along the U.S.-Mexico border, as well as in Puerto Rico.

NIAID allocated $33.2 million for dengue research in 2007, specifying funding for nearly 60 research projects and vaccine development efforts.

Late last year, the American Public Health Association announced a new initiative to tackle the effects of climate change, which it said represents "one of the most serious public health threats facing our nation." The American Academy of Pediatrics expressed similar concern last fall when it warned that children will face the greatest health threats from global warming.

Other vector-borne diseases that could become more prevalent as temperature rise include malaria, Lyme disease and hantavirus pulmonary syndrome. Respiratory problems could also increase as the levels of pollutants and allergens in the atmosphere increase, scientists warn.