The soft cries of children broke the morning stillness as parents brought them to the hillside hospital one by one -- feverish, racked by chills, drained by a disease once unknown in the high country of Kenya.
Just outside town later that day, scientist James Mutunga scooped water from an irrigation ditch, poured it into a plastic basin and leaned down to look with a practiced eye.
"See, here, there's a larva. This one's about a day old," he said, scanning the murk for tiny, newly hatched Anopheles arabiensis, a malaria-bearing mosquito rarely found in Kenya's uplands.
Last year, Mutunga's team detected them nearby at an altitude of 6,243 feet. "That's the highest ever in Kenya," the young entomologist said.
Painstaking work remains before conclusions can be reached. But Kenyan and international researchers are moving closer to showing that climate change -- rising temperatures -- is tied to malaria's spread into African highlands that long were largely free of the ancient disease.
People here already seem to know it.
"It's because the temperatures are going up," farmer Patrick Kabugu, 49, said as he watched Mutunga hunt for larvae in his lush, green field of corn and cassava.
The bite of a female anopheles, transmitting the malaria parasite to the human bloodstream, leads to the deaths of more than 1 million people worldwide each year, an estimated 75% of them African children, international health authorities report.
Here in Karatina, amid coffee plantations on the slopes of Mt. Kenya, 50 miles north of Nairobi, people a decade ago began noticing an upsurge in malaria, beyond the usual cases of travelers from the warmer lowlands.
"It's increased a lot -- I'd say five times as much as just a couple of years ago," nurse Gladys Wachira told a visitor to the hospital's pediatrics ward, a sparsely equipped, unheated building where mothers in coats lay atop beds with their ailing children, undergoing treatment with antimalarial drugs.
The hospital's medical superintendent, Dr. Roseline Atienu, estimated that 60% of child patients today have malaria. "This is not supposed to be a malarial area. Now it's our No. 2 problem, behind pneumonia," she said.
The Intergovernmental Panel on Climate Change, a United Nations network of climate scientists, has long projected that mosquito-borne tropical diseases would spread to new areas that grew warmer. The malaria parasite needs temperatures above 64 degrees to develop.
"There is a known climate envelope for this disease that requires warm temperatures," said Dr. Jonathan Patz, a University of Wisconsin expert on climate-disease links. He said of malaria's predicted spread: "In some ways it is common sense."
The pattern seems to be unfolding in East Africa, where researchers have reported malaria epidemics in recent years in the highlands of six countries. In one west Kenyan district between 1986 and 1998, cases rose to 120 per 1,000 people annually from 16 per 1,000.
But establishing a link requires data of a quality seldom found in Africa. In a widely cited 2002 scientific paper, British-led researchers said temperatures had not risen at four epidemic sites in the East African highlands. That finding was disputed last April, however, by other researchers who said refined data show those locations had grown warmer by almost one degree since the 1970s.