Coming to America: Neglected tropical diseases taking hold in U.S.

As public health officials continue to make connections between health and societal factors, there's mounting evidence that diseases once considered exotic are taking root in the poorest areas of the U.S.

“We already have dengue (and chikungunya) in Texas and in the Gulf Coast, and I think we'll start to see transmission of both diseases in the coming years,” said Dr. Peter Hotez, founding dean of the National School of Tropical Medicine at Baylor University's College of Medicine.

Hotez estimated that as many as 12 million people in the U.S. live with a neglected tropical disease, defined by the Centers for Disease Control and Prevention as a group of parasitic and bacterial diseases that cause illness in as many as 1 billion people worldwide.

Referred to as neglected because they have been around for years without much attention toward their prevention or treatment, neglected tropical diseases can go unnoticed with few or mild symptoms and low rates of mortality. But they can also be debilitating and could impair physical and cognitive development in children who may already be facing other challenges.

Hotez's institution addresses how poor housing conditions, inadequate sanitation and contaminated environments make impoverished communities more susceptible to neglected tropical diseases.

A 2014 study authored by Hotez and published in the journal PLOS found that tropical disease was prevalent among the poorest populations living in the world's top 20 major economies.

In the U.S., many of the nation's 45 million impoverished Americans live in warm, humid Southern states where mosquitoes, often the carriers of these diseases, thrive, said Dr. Susan McLellan, associate professor of tropical medicine at Tulane University School of Medicine.

Since 2006, the U.S. has helped fund a global effort to donate drugs that prevent or treat the seven most prevalent neglected tropical diseases, including hookworm, trachoma, river blindness and elephantiasis.

The program also addresses environmental factors, such as access to clean water.

But many of those approaches are not employed in the U.S., where there's a lack of awareness of the prevalence of tropical diseases and the devastation felt in impoverished areas.

Cases of chikungunya, for which there is no vaccine or cure, have been steadily rising in the U.S. since the first confirmed case in the Western Hemisphere was identified in 2013. Endemic in Africa and Asia for decades, the number of U.S. cases reached more than 2,700 last year, according to the CDC. As of last week, 39 states had reported a total of 510 cases this year.

Dengue fever, a disease that's affected 300 million people in Southeast Asia and Latin America, has been of particular concern to U.S. epidemiologists.

Florida and Texas have had increased sightings of the mosquito type known as the primary carrier of the disease—Aedes aegypti. That means there's a greater chance it will become native in warm climates throughout the U.S., where stagnant bodies of water create the perfect breeding ground for mosquitoes.

And experts say that as diseases mutate, mosquitoes more common throughout other parts of the country can become carriers.

Hotez said the Ebola outbreak last year spotlights the need for more forward thinking in addressing potential disease threats. Critics have said the relief effort in West Africa was insufficient and late in preventing the spread of the epidemic. Others have criticized drugmakers for not quickly developing an Ebola vaccine, which is still undergoing clinical trials.

And then there's the issue of hospital preparedness, another critique of the Ebola response. It was a Dallas hospital that was accused of not following the right protocol to keep hospital staff safe. In fact, many hospitals in high-risk areas have few resources to deal with public-health crises such as tropical disease.

The same is true of state public health departments.

A 2014 report from the Robert Wood Johnson Foundation found that only half of states scored adequately on their ability to detect, diagnose, prevent and respond to a disease threat.

In Louisiana, which reported 10 cases of chikungunya and one case of dengue fever last year, the average annual amount spent on public health for each resident is about $15. That ranks the state 39th in the U.S., according to the American Public Health Association.

However, all signs seem to indicate more attention is being placed on tropical disease outbreaks in the U.S. The world's top infectious disease experts will gather this month for the annual meeting of the American Society of Tropical Medicine and Hygiene. They are expected to present breakthroughs in improving the ability to understand how diseases work and ways the global community can prepare for the next potential pandemic.

Hotez said tropical diseases remain largely neglected in the U.S. because they still mostly affect the poorest individuals. He says a call for action may come only when such diseases become widespread.

“It's an inconvenient truth many people don't want to recognize,” Hotez said.