Amid continuing debate over the health consequences of climate change, specifically the spread of vector-borne afflictions like malaria, scientists reported growing cases in the highlands that correspond to higher temperatures.

"Malaria is the most climate-sensitive, vector-borne disease affecting most of the African population," said Andrew Githeko, a researcher with Kenya Medical Research Institute (KEMRI).

"Both global warming and increased climate variability can increase malaria transmission," he told AFP on the sidelines of the 12th UN conference of parties to the UN Framework Convention on Climate Change (UNFCCC) in Nairobi.

At least 15 Kenyan highland districts, compared to three in 1998, are now malaria-prone, with the most affected being Nandi Hills in the Rift Valley, Kisii in western Kenya and the central Mount Kenya region, according to KEMRI.

The first cases of malaria in these districts, prevously free of the disease as cooler weather at higher altitude kept malaria-carrying mosquitos away, occurred in the 1980s and have steadily increased over the years, it said.

"We have started to experience malaria outside the usual prevalence area," said Grace Akumu, director of Climate Network Africa, a local non-governmental organisation.

In 1997, authorities reported a 250-percent surge in cases in the highland districts at the height of the 1997-1998 El Nino-associated rains that pummelled the country.

In 2002, a malaria epidemic killed 800 people in Kisii alone and 2,000 others in neighbouring districts, a situation compounded by the fact that highland residents having weaker immunity because unlike their lowland cousins they have not usually been exposed to the malaria parasite.

The outbreaks, that even saw malaria break out last year during Kenya's coldest June to August season, corresponds to the latter stages of a 0.5 degree Celsius rise in highland temperatures over the past 20 years, they said.

"With global warming, people in the highlands are mostly affected," said John Githure, head of human health division of the International Centre for Insect Physiology and Ecology (ICIPE).

"These highlands continue to have higher and higher temperatures," he told AFP. "We are very worried about what is going to happen if the average temperature increases further."

"It is the areas where transmission is currently low, such as the highlands that are most affected," he added.

But theory is not universally accepted and some scientists have sought to debunk any causal link between malaria and global warming, blaming the increase on changes in human behaviour and the dynamics of the spread of the disease.

"I am not a defender of the link between malaria and climate change," said Francois Omlin, another ICIPE scientist, attributing it to "the influence of people towards shaping their environment and the changing behaviour of mosquitoes."

Among other possible simple causes, he said basic human activity, such as brickmakers in Kisii who leave open trenches that collect water during rainy season and provide breeding grounds for the malaria mosquitos could be blamed.

Omlin and other naysayers insist that statistics to back up a climate change-malaria link are scant and point to factors such as drug and pesticide resistance that cannot be ruled out.

Still, the number of malaria cases in the Kenyan highlands is steadily rising and experts believe the current October to November short rain season, which forecasters say may extend to early January, combined with warm December temperatures, is likely to spark another surge.

"We expect an increase of between 50 to 100 percent of malaria cases from the end of November," said Githeko.

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