Could malaria recolonize the West?

It depends.

The malaria parasite continually invades its former stomping grounds, in the 1,200 malarial travelers, refugees, soldiers, and miners that toss and turn on American hospital and clinic beds every year. Little besides sheer metal mesh prevent the parasites from re-entering the hungry Anopheles mosquitoes outside, re-igniting an epidemic. Anopheles flit in every state of the U.S. union, save for Hawaii, and the swarms double in size for every half-degree uptick in the global temperature.

A tsunami of people carrying Plasmodium from Africa and Asia show up in Europe every year. Today, eight times more malaria patients arrive at clinics and hospitals across Europe than did in the 1970s. Back then, most of the Plasmodium imported into Europe were of the vivax strain. Now, nearly 70 percent are deadly falciparum.

What would it take for the anophelines of Europe to start transmitting the parasite once again? Perhaps if Russia once again cut off Europe’s natural gas supply, as it did in the winter of 2006, rendering a black-out that might stall the water pumps, disabling health care facilities while creating new mosquito habitat in hidden and unexpected places. Or a distracting health emergency, like the 2003 heat wave that killed over 30,000 Europeans over the course of a single season.

The entire economy, experts say, would have to break down in order for malaria to resettle in the United States. And yet, mosquito-borne West Nile Virus and Japanese encephalitis have spread, as we’ve watched with our eyes peeled and wallets open. In 2002, California had one single case of West Nile virus; in 2003, there were 3, according to the CDC. By 2004, there were 779; in 2005, 873. The economy survives, despite it. It tolerates, too, those pockets of humid, neglected anarchy where Plasmodium builds its strongholds, such as the drowned cities of the south, deprived of electricity and order in the wake of the 2005 hurricanes.

Malaria is one of the most infectious diseases of humankind, seven times more infectious than measles and dozens of times more infectious than HIV. A single fevered human with malaria parasites infesting his blood can infect 100 people with malaria.

Globally, at least 17 of the 60 species of Anopheles that carry malaria had developed the ability to resist DDT and related compounds.