Even as the incidence of fresh cases of Nipah virus has come down, a woman, under treatment at the Kozhikode Medical College hospital, passed away on Saturday, taking the disease toll in Kerala to 13, officials said.Kalayani, 62, had been admitted to the hospital on May 16.A majority of the deaths have been reported from Kozhikode, while the others are in the nearby Malappuram district.Close to 200 patients in these two districts are being treated in hospitals, with 26 under observation and three who have tested positive under intensive treatment.Meanwhile, five medical professionals are being sent to Delhi for an intensive course at the Safdarjung Hospital there to learn the treatment protocols to be followed in such cases.Nipah virus is transmitted to humans through infected fruit bats, pigs or other Nipah-infected persons.With test results showing that a particular variety of bats, found in and around Kozhikode and mostly at the worst-affected Perambara town near here, is not carrying the virus, a special team from Pune is arriving to see how best they can take samples from other varieties of bats also found in this district.In a related development, a police probe, initiated to find out the travel itinerary of the virus' first victim Sabith, found out that he never visited Malaysia but had been in the United Arab Emirates, from where he had returned in October last year.