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Increased travel may lead to further spread of malaria
In the past few years, malaria cases have been reported in areas where the disease is not endemic.
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NEW ORLEANS – Increased travel and globalization may be helping foster the spread of malaria. Public health experts have become increasingly concerned about the spread of malaria in areas where the disease is not endemic. In recent years, malaria outbreaks have been reported in the United States and Western Europe.
At the American Society of Tropical Medicine and Hygiene’s 57th Annual Meeting, held here in December, James H. Diaz, MD, director for environmental and occupational health at Louisiana State University in Baton Rouge, spoke about the increasing rates of malaria and its association with travel.
Three types of malaria
Diaz said there are three types of malaria in the United States today: imported malaria, autochthonous malaria and airport malaria.
Imported malaria occurs when a person infected with malaria gets on a plane in a malaria-endemic area of the world and comes to the United States. “Such cases are increasing worldwide,” Diaz said. “According to WHO, imported malaria now accounts for about 33,000 cases of malaria per year. This is now the most common type of malaria in the United States.”
Autochthonous malaria is also referred to as “locally-transmitted malaria.” According to Diaz, this type of malaria occurs when a local female Anopheles species mosquito in the United States bites a person infected with malaria, then bites someone else, thus transmitting the disease. “This type of malaria has recently been reported in California, Texas and elsewhere,” Diaz said. “These cases are few but increasing in the United States and Europe. This is of concern because a mosquito-borne disease can be newly-introduced or even re-introduced into a formerly endemic region.”
Airport malaria is the least common form of malaria, although it has recently received increased attention in the media. Airport malaria occurs when an infected mosquito (a pregnant female Anopheles species) gets on a plane in an endemic country bound for a nonendemic country, survives the journey – including the changes in cabin pressure and low humidity on the flight – and lands at the destination and bites someone in the vicinity of the international airport. “This is very, very rare,” Diaz said. “Such cases have been documented in London and Paris. But most planes on international flights get fumigated before departing malarious areas of the world, though some do not.”
Important concerns
In an interview with Infectious Disease News, Diaz noted that airport malaria has gained more attention in recent years. But this should not be the most pressing concern.
“We have to stop worrying about the airport malaria cases, which are very rare since not many pregnant female Anopheles mosquitoes could survive a long international flight,” he said. “We need to worry about the increasing number of imported malaria cases and then autochthonous malaria.”
Diaz said since malaria only has a reservoir in humans, efforts to stop the spread of the disease should be aimed at improved diagnoses and early and optimal treatments. He also said people traveling in endemic areas should be warned about proper protection against malaria. “People should protect themselves from the vector mosquitoes when traveling in malarious areas and seek immediate medical attention if they have a fever,” he said.
Disease spread
Increased travel, globalization and climate change may all be contributing to the spread of diseases in a way that has never been seen.
“We are now one world and it is getting smaller every day,” Diaz said. “And when we are one world in a warming and welcoming ecosystem, we can no longer ignore or neglect tropical diseases because they are becoming increasingly more likely to spread. Recent examples include SARS, West Nile virus and imported malaria.”
Diaz cited examples from the past to explain how trends in travel and trade can influence the spread of disease. “International travel and trade in a warming ecosystem may foster the spread of infectious diseases throughout the world, similarly to when the New World was settled,” he said. “But today the Old World and New World are one.” – by Jay Lewis
For more information:
- Diaz J. Global climate changes, natural disasters and travel health risks. Presented at: The American Society of Tropical Medicine and Hygiene’s 57th Annual Meeting; Dec. 7-11, 2008; New Orleans.