A 23-year-old college student, admitted in a private hospital in Kerala's Ernakulam, has tested positive for the deadly Nipah virus, which killed 17 people in the state last year. The National Institute of Virology, which tested his blood samples, confirmed the presence of the virus, the government said today. Four more people, including two nurses, are down with fever and two of them had come in contact with the 23-year-old man. Over 80 people, among them 22 students, are under surveillance.