Infection Decline in Infection in Decline Decline Decline BRITISH birds including sparrows, chaffinches and nightingales are dying from malaria in a wave of infection that is believed to be caused by climate change.  at least 30 common types of bird are now infected. In some species the disease was unknown as recently as the mid-1990s but is now being regularly diagnosed by monitoring projects. Only 20 years ago less than 10% of house sparrows in Britain were infected. That figure has now reached 30% and is rising rapidly.  The screening of birds such as blue tits, great tits and owls has shown even greater proportionate increases since the mid-1990s, when almost none were infected.  The bird form of malaria cannot be transmitted to humans but, just like human malaria, it kills by destroying oxygen-carrying red blood cells and is transmitted by mosquito bites. The rapid growth in mosquito populations is being attributed to a rise of about 1C in global average temperature.  The study that identified this new epidemic was carried out by Laszlo Garamszegi, a world expert on avian malaria who is attached to the Spanish government's Do?ana biological station near Seville.  In the largest analysis carried out so far, Garamszegi compared malaria infection data from more than 3,000 species around the world, dating back to 1944. The results have just been published in the journal Global Change Biology.  The findings follow disturbing studies from the Royal Society for the Protection of Birds that reveal a fall of up to 68% in the British house sparrow population since the mid-1990s. a survey of nightingales by the British Trust for Ornithology found a 90% decline in the past 40 years. The studies have raised concern that the birds face extinction.  It is not possible to establish any link between bird malaria and the dramatic decline in numbers. "We don't know how many of the heavily infected birds die before they can pass on the infection," Garamszegi said, "but it does show trends we ought to be worried about."  Ben Sheldon, professor of ornithology at Oxford University, is also concerned. "There is very convincing evidence that a wide range of biological processes are altering in response to changing climate," he said. "Malaria is a significant cause of mortality, but how it is transmitted is not straightforward. It is quite hard to predict."  Matt Wood, a bioscientist at the University of Gloucester who has tracked malaria infection among blue tits, said there was at present no way of knowing how virulent a new strain of the disease could become.  "Things are changing very fast and we need to understand much more about which mosquito specie