‘Bad Air’: Malaria’s Temperate Return

A day without a car would be difficult for many Americans – even the most earnest, intrepid, or eco-conscious. So, how about a day with little food, unsafe water, and polluted air? Add a debilitating vector-borne illness such as malaria to this devil’s brew, and you have a glimpse into the potential impacts of climate change on human health.

Climate change scientists are vigorously amassing mountainous data to demonstrate the impacts of climate change on numerous threatened or endangered species – think polar bears – but have only just begun to extensively study human health outcomes. When an ice shelf nearly the size of Manhattan breaks away from Ellesmere Island in Canada’s northern Arctic, the US fire season lengthens 78 days over 20 years, and the three hottest years on record – including the 2003 European heat wave which claimed 15,000 lives – have all occurred within the last decade, humans should no longer have to guess about our own fates.

The World Meteorological Organization/United Nations Environment Programme (UNEP) Intergovernmental Panel on Climate Change (IPCC), co-winners with Al Gore of the 2007 Nobel Peace Price, and the World Health Organization (WHO) have each warned the Himalayan glaciers supplying the Ganges, Yellow, and Yangtze rivers could disappear by 2035 (see IPCC Assessment Reports). These melting glaciers will cause food and water shortages in our planet’s two most populous nations, India and China. Similar scenarios hold true for other regions. The UNEP Global Environment Outlook, 4th Edition (GEO-4) reports almost one third of the global population could be at risk from the resultant increasing desertification and declining agricultural production.

Elevated temperatures increase the amount of both atmospheric ozone and low-lying air pollutants, in turn raising the occurrence of respiratory illnesses such as asthma. Several UNEP reports on climate change and vector-borne illnesses, including studies originally performed in 1995 and reaffirmed with the IPCC’s work in 2007, note a “likelihood of altered distribution of many major tropical vector-borne and other infectious diseases – such as malaria and dengue fever.”

Given the sheer volume of disturbing climate statistics and scenarios, why are there relatively few health-climate studies? The paucity of federally funded research to study any aspect of climate change on human health provides a partial explanation and leads to the topic’s remaining largely shrouded in mystery. We can begin to glean some ideas by extrapolating the findings from existing international climate change studies and pairing them with our knowledge of public health.

The United States hasn’t always been willfully and woefully oblivious to relationships between health and the environment. The Centers for Disease Control and Prevention (CDC), originally known as the Communicable Disease Center, stems from the 1942 Malaria Control in War Areas (MCWA) program. The MCWA’s goal was to eradicate malaria from military training bases in the southeastern United States and its territories where mosquitoes were still abundant. The MCWA also aimed to prevent reintroduction of malaria into the civilian population by way of mosquitoes that would have fed on malaria-infected soldiers.

The National Malaria Eradication Program (NMEP), a cooperative undertaken by the public health agencies of 13 southeastern states and the CDC, continued operations after the end of World War II. The NMEP’s programs included aerial and household spraying of dicholo-diphenyl-trichloroethane (DDT) and the drainage of stagnant water mosquito breeding sites as prior experiences linked malaria reduction to mosquito control. Malaria, endemic to the southern United States until it was considered eradicated in 1951, is one of the principal reasons CDC is located in Atlanta, not Washington, D.C.

Malaria: Understanding its Routes and Impacts

Female Anopheles mosquitoes transport the malaria parasite from one human to another via their salivary glands. They must take a blood meal to complete egg production, hence creating the crucial human-vector link. In the Americas, Anopheles mosquitoes play host to Plasmodium Vivax, the most widely distributed form of malaria.

P. Vivax is the most common of the four human malaria species because of its ability to survive in the world’s temperate regions, including Europe and North America. The term malaria originates from Medieval Italian: mala aria – “bad air.” Also known as recurring or tertian malaria, P. Vivax is noteworthy for its morbidity – severe, debilitating paroxysms, rigors, fevers, and headaches – not its mortality. P. Vivax‘s relapsing characteristic is related not only to the blood parasite’s two-day life cycle but also the liver parasite’s reintroduction into the bloodstream, a process known as recrudescence, experienced by survivors up to three years after the original infection. Ultimately, P. Vivax malaria was eradicated from the southeastern United States through a combination of socioeconomic improvements, effective treatments, and vector reduction, not by eliminating the female Anopheles mosquito – which remains abundant throughout the Southeast.

Because malaria remains endemic in most of the Southern Hemisphere, and is found as close as southern Mexico, CDC acknowledges that reintroduction of malaria remains a constant risk. Further, the Anopheles mosquito is now resistant to DDT, and malaria treatment is hampered by increasing drug resistance. The combination of these factors means that any new domestic malaria outbreak would have to be managed under new vector control and drug treatment paradigms.

The 2007 IPCC report examines how human health both has been affected and potentially will be affected by climate change. The authors note specific limitations of the analyses they conducted, such as changes in reporting, surveillance, or land use, and they conclude by urging further research. The United States has yet to even perform a comparable study – the data isn’t limited, it’s non-existent.

A July 2007 National Geographic malaria article and a Washington Post front-page piece in December of that same year offer examples of excellent pieces of reporting that can draw only crude conclusions as a result of the glaring lack of scientific data.

The American public is left uninformed and in the dark. The disconnect between climate change and human health is reflected in American public opinion surveys. Understanding the potential linkages between a fossil fuel powered car’s carbon dioxide emissions and a changing climate could lead to better understanding of potential health impacts of climate change. Information and recognition are the first steps to cure, and that first step has already been taken by many throughout the industrialized world.

Among the potential solutions for preventing malaria’s return, business and behavior modifications based on sound scientific evidence could be key. When it comes to better understanding the relationships between climate change and human health, ignorance is not an option.

CDC Graphic

Source: CDC website

Leslie King, MD, MPH, is Founding Director of Flying Physicians International. She currently is completing a one-year mid-career masters at the Yale School of Forestry and Environmental Studies, focusing on communications on impacts of climate change on human health.

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2 Responses to ‘Bad Air’: Malaria’s Temperate Return

  1. Leslie P. King says:

    Dear Dr Brown,
    Thanks for taking the time to read and comment upon my malaria article. Thanks also for the links to additional material germane to my climate change interests. I’m certain it will have some future use.
    ~LPK

  2. jean says:

    Thanks for your article, but in fact I am curious about health problems long ago (18th & 19th C>)
    believed to be caused by malaria have now ceased. I am wondering if the disease was mis-diagnosed in the beginning or if some other “cure” was used. Not all marshy areas were filled in.
    For example, I live in Toronto and long ago there was a problem of this sort for people wo lived aloong the lakeshore.

    Do you have any ideas on this issue?

    Many thanks