Six patients admitted in a quarantine facility at the Government Medical College in Ernakulam, Kerala, have tested negative for the Nipah infection. The state’s Health Minister KK Shailaja on Thursday said the National Institute of Virology in Pune has cleared their samples, The News Minute reported.

The samples of the six people had earlier tested negative for Nipah virus at the National Institute of Virology laboratory in Alappuzha. The state government, however, sent the samples to Pune for a final confirmation. Shailaja said the six people are still under observation and will not be discharged as yet. She said the samples of a seventh person who is under observation will be sent for tests on Thursday.

A 23-year-old student had tested positive for Nipah virus in Kochi on Tuesday. Six people, including three nurses who treated the 23-year-old, showed symptoms of the infection and were were shifted to isolation wards and around 311 others who came in contact with the student are under observation to prevent the disease from spreading. Health officials have yet to find the source of the virus.

Nipah is a virus that can be transferred from animals to humans. It causes fever and cold-like symptoms in patients before quickly advancing to encephalitis, which is inflammation of the brain, and myocarditis, or inflammation of the heart. There is no vaccine or cure for Nipah infections at present. An outbreak of the virus in Kerala in May 2018 had claimed 17 lives.

Kerala’s Principal Health Secretary Rajan N Khobragade said the state government has gathered the phone numbers and addresses of 149 people on the contact list for Nipah virus. The contact list includes people who came in direct or indirect contact with the patient at any point of time in the last three weeks.

“Among the 149 contacted, we got full data of 35 people whereas partial details for the remaining 94,” Khobragade said. “It will be completely collected by Thursday. Among the 35 people whose full details have been received, three of them are in the ‘high risk’ category.”