No creature on earth has so directly and profoundly touched the I ives of so many people as the mosquito. It delivers more illness to humanity than any other single agent. Quentin Coopertalksto Dr Andrew Spielman about man's strange relationship with this tiny harbinger of death. He discovers how humans have inadvertently been responsible for helping the mosquito spread disease and what now has to be done to stop them. Producer Fiona Roberts. E-MAIL: material.world@bbc.co.uk