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Forecast: Pathogens find new habitats

Part 2: The spread of disease

Worker Solomon Conteh picks up a mosquito at Sanaria Inc. facility in Rockville, Md., Oct. 26, 2007. The insects in the facility are dissected for the motherlode that they carry — baby malaria parasites. (Jim Young/Reuters)

There is a link between climate change and the global health crisis. In Africa and Asia, global warming is driving pathogens into new habitats and facilitating the outbreak of exotic and often deadly diseases.

LAGOS, Nigeria — I caught malaria twice here.

I cured it early both times, before it had time to gather strength. Nonetheless, it knocked me down.

Walking to the clinic for a blood sample during the second attack, I vomited on the road. That night, on a friend’s couch, my bones ran cold, my skin shivered, my shirt changed color with sweat. It was two days before I was ready to work again.

As temperatures increase, regions that once were free of disease-carrying mosquitoes will become suitable for the insects.

“We’re seeing changes in the range of mosquitoes and the diseases they carry,” said Paul Epstein, associate director of the Center for Health and the Global Environment at Harvard Medical School.

“That’s going to be an issue increasingly in terms of latitude and on the margins, both in terms of extensions of the range and in terms of seasonality,” he said.

Mosquito larvae mature more rapidly when the water in which they grow is warm. Female mosquitoes digest blood faster and bite more frequently as the mercury rises.

The cycle begins when mosquitoes ingest malaria parasites — the parasites split into males and females, reproduce in the mosquito’s gut, and release snake-shaped sporozoites that migrate to its salivary gland, ready to be injected when the insect bites a new human. Malaria transmission begins when a mosquito feeds on an infected person. 

A malaria mosquito will only live a few weeks.

The parasite’s survival depends on it reaching maturity while its host is still alive to bite.

The strain of malaria I caught is called Plasmodium falciparum. In temperatures of 68 degrees Fahrenheit, the parasite takes 26 days to complete its reproductive cycle. At 77 degrees Fahrenheit, it’s ready to reinfect after just 13 days.