Fruit bats may not be the cause of the brain-damaging NIPAH (NiV) virus that killed 12 people and infected 20 in southern Kerala, a medical test report has said. The blood and serum samples of 21 bats tested at the National Institute of High Security Animal Diseases in Bhopal returned negative results for the virus, officials said. Health officials linked the initial deaths to a well colonised by bats at a house in Kerala's Kozihikode where the four members of a family died of the rare Nipah virus.