There's a lot we can attribute to global warming - melting ice caps, displaced animals, climate change deniers. Now there's another to add to the ever-growing list: escalating rates of malaria transmission.
British and American researchers looked at patterns of the mosquito-borne disease from 1990 to 2005, monitoring changing temperatures throughout the fifteen-year period. Titled Altitudinal Changes in Malaria Incidence in Highlands of Ethiopia and Colombia, the study found that an increase in temperature of one degree Celsius in Ethiopia could result in an addition three million cases of malaria annually - and that's just in patients aged 15 years and under.
Cooler years saw the median number of malaria cases lower, while warmer years were accompanied by a higher incidence of the disease. Crucially, the team also looked at the average altitude where cases occurred, revealing that towns elevated from sea level were more susceptible as temperatures and humidity increased. In addition, the towns prone to higher incidence of the disease are densely populated, meaning that a larger proportion of people will likely contract malaria.
The discovery comes amid fears that tropical dwellers are at a heightened risk of contracting disease, as rising temperatures make already mosquito-friendly conditions yet more welcoming to the critters - and more threatening to the local population. Observing the Antioquia region of western Colombia from 1990 to 2005 and the Debre Zeit area of central Ethiopia from 1993 to 2005, the disease was found to be prevalent in countries were medical access isn't necessarily readily available. Once contracted, the disease often leads to severe complications, and can result in death. Even with treatment, prognosis is typically touch-and-go.
"This is indisputable evidence of a climate effect," said University of Michigan theoretical ecologist, and study leader, Mercedes Pascual. "The main implication is that with warmer temperatures, we expect to see a higher number of people exposed to the risk of malaria in tropical highland areas like these."
"We showed that highland malaria in both Ethiopia and Colombia basically moves up in altitude in warmer years," Pascual said to Newsweek. "And the importance of this is that climate change will, without mitigation, result in an increase of malaria burden in these densely populated highlands of Africa and South America."
Menno Bouma, honorary senior clinical lecturer at the London School of Hygiene and Tropical Medicine, concurred with Pascual's statement. "Our latest research suggests that with progressive global warming, malaria will creep up the mountains and spread to new high-altitude areas," he said to the Agence France-Presse. And because these populations lack protective immunity, they will be particularly vulnerable to severe morbidity and mortality," he said.
Malaria is not the only disease that's been linked to a warmer planet. Dengue fever, also carried by mosquitoes, has the same dubious honor. Dengue fever has also been found in the United States - a far cry from the typical stomping grounds of Asia and Africa. South America remains a hotspot for the anopheles mosquitoes that carry the protozoa disease, with the species migrating up towards the Caribbean and beyond to broach the North American border as climes become more temperate - and thus more welcoming - for them to thrive in.
Dr. William Moss, an epidemiology professor and member of the Johns Hopkins Malaria Research Institute, spoke to Newsweek about his experiences as a malaria sufferer - and, now, survivor. Moss cautioned that rising temperatures aren't the only factor in fostering mosquito veracity and population growth; indeed, he also pointed to a growing resistance to insecticides making the species all the more aggressive.
"My main take-home message on this," he said. "Is that what this article highlights is that the epidemiology or distribution of malaria is a dynamic thing. And temperature changes may be one thing that is driving the changing burden of malaria."
