With increasing numbers of mosquitoes in the U.S. carrying the West Nile and dengue viruses, it’s getting a little scary to go outside.

West Nile is poised to break records this year. Almost 1,600 cases have been reported to the Centers for Disease Control and Prevention so far, including 66 deaths. The virus has been in the U.S. since 1999, sickening 30,000 altogether; this year the worst outbreak has been centered around Dallas.

West Nile’s cousin, dengue, also a sometimes fatal infection, has been in the U.S. since 1980, with outbreaks in Texas, Hawaii and Florida, most recently in 2010.

These are growing public-health problems, but they can also serve as opportunities to pull the U.S. squarely into the global fight against these mosquito-borne viruses.

Identified only in 1937, West Nile is a disease mainly of Africa, the Mideast and parts of Asia. Severe infections lead to brain diseases such as meningitis and encephalitis. Dengue, known as breakbone fever for the muscle and joint pain it causes, can lead to dengue hemorraghic fever and the sometimes fatal dengue shock syndrome. As many as 100 million people are infected worldwide every year.

The two illnesses have come to the U.S. courtesy of climate change and globalization. Rising temperatures promote mosquito reproduction and survival. And infected mosquitoes easily travel via the cross-border exchange of goods. Globe-trotting people, for their part, carry viruses from endemic to nonendemic zones. (Neither dengue nor West Nile spreads directly from person to person, but a mosquito can transmit the viruses from one person to another.)

Health authorities have few good measures to cope with either disease, and are reduced to asking people in vulnerable communities to avoid exposure to mosquitoes by staying indoors in air-conditioned or well-screened quarters, wearing long pants and sleeves in the heat of summer, and using mosquito repellant. They counsel households to eliminate places where mosquitoes lay eggs, notably artificial containers that hold water.

When outbreaks occur, officials apply insecticides on the ground or by air if the affected zone is large. Yet today’s formulas don’t pack nearly the wallop of those 50 years ago, which contained DDT. DDT practically eliminated the dengue-carrying Aedes aegypti mosquito from the U.S. but also savaged bird species, which is why it is now banned.

Patients receive acetaminophen for fever and pain, fluids if they are dehydrated, and get-well wishes. No vaccines, no cures and no specific medicines exist to prevent or treat dengue or West Nile.

That is not uncommon for illnesses that predominantly affect the developing world. Companies with the know-how to develop such products have generally lacked the profit motive to make the necessary investments, given that sales would be mainly in poor countries.

This failure of the market points to the need for other mechanisms. Thankfully, they exist. The U.S. government invests directly in neglected-disease research, principally through the National Institutes of Health. It also supports nonprofit organizations called product development partnerships that spur innovation and bring products for neglected diseases to market. These groups, which work in concert with private-sector partners, were responsible for almost half of the 45 new global health products to treat a range of illnesses registered from 2000 to 2010.

Traditionally, government spending on neglected diseases has been seen as charity or foreign assistance. Now it must become a public-health priority for the sake of Americans, as well.

Thanks in large part to the efforts of the Dengue Vaccine Initiative, a product development partnership, four experimental dengue vaccines are now undergoing trials. Yet only a few medicines to treat dengue are in the early stages of development. And research to address West Nile virus is embryonic. Funding is needed to study better methods of controlling the types of mosquitoes that spread the two viruses; especially promising is the development of genetically modified bugs that would wipe out their own species or be incapable of carrying disease.

Although the U.S. is the largest funder of neglected-disease research, its spending declined 5.1 percent in 2010, according to an annual survey conducted by the research group Policy Cures. As the U.S. outbreaks of West Nile and dengue show, this spending is now a vital investment in the health of American citizens.

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Today’s highlights: the editors on the Democrats’ hard task; Jeffrey Goldberg on confronting potential genocides; William Pesek on this weekend’s Asia-Pacific Economic Cooperation Conference; Ramesh Ponnuru on how hard an Obama second term would be; Cass R. Sunstein on how voters can escape from their political cocoons; John H. Cochrane on Keynesian assumptions at the Congressional Budget Office.

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