 Climate change could extend the pollen season and encourage more disease-carrying ticks in northern Europe, and allow mosquitoes to thrive in new areas of Africa and Asia, public health officials said this week. Experts at the World Health Organisation's (WHO) annual assembly in Geneva said global warming had already begun to impact on patterns of water-borne and parasitic illness in areas vulnerable to droughts and floods. Respiratory and heart problems may become more marked following heat waves and increased particulate matter such as dust in the air, said Bettina Menne of the WHO's European division. She noted allergy-causing pollen could be released earlier and last longer with warmer temperatures. She cited the movement of ticks, small mites that can spread lyme disease, into northern Europe as an example of new health challenges that will accompany the continual heating-up of the Earth, a phenomenon scientists have linked to human activity. "Climate change has already affected human health," she told a WHO technical meeting on Monday evening. Outbreaks of cholera and malaria in the developing world were a result of environmental shifts affecting parasites and water sources, she said. South Asia was described in the session as particularly at risk because of its flood-prone low-lying countries such as Bangladesh, melting Himalayan glaciers, desert areas and large coastal cities, where climate change could facilitate disease transmission and exacerbate malnutrition pressures. Maria Neira, the WHO's director for public health and the environment, said it was critical for policy-makers to remember that climate change would have a broader impact than often-discussed environmental and economic threats. Health experts should be more involved in decision-making on energy use and conservation, and should impress upon political leaders the need for more emergency preparedness in health, such as the fast distribution of malaria nets and drugs, Neira said. "The health community, more and more, needs to influence and be present when those decisions are taken," she said.