The mother of the two girls who died in the space of four days due to an yet unknown disease has fallen sick in isolation at Rajshahi Medical College Hospital.

The father, Manzur Rahman, was still doing well in isolation on Sunday.

The Institute of Epidemiology, Disease Control and Research has dispatched an expert team to Rajshahi to find out the cause of the deaths of the two sisters as the Nipah virus test result came out negative.

Manzur, a teacher of Rajshahi Cadet College, his wife Poly Khatun, and daughters Muftaul Mashia and Muntaha Marisha lived in the college quarters.

Mashia was to turn 5 on May 30, while Marisha 2 on Mar 2, but the elder sister died in the hospital on Saturday after the younger’s death last Wednesday on the way to the hospital.

Nipah virus generally spreads through raw date juice that contains the excrement or saliva of infected bats. Anyone who drinks infected juice will get the disease.

The Directorate General of Health Services warned people against eating fruits partially eaten by birds or bats, consuming raw date juice, and advised them to wash fruits well with water before eating.

Doctors had suspected the two sisters caught Nipah virus as they ate unwashed plums collected from under a tree a day before falling ill.

Marisha first caught fever and started to drink water frequently before vomiting. Mashia had similar symptoms, including dark rashes.

After the elder sister’s death, the doctors did not let the parents go and kept them in isolation.

Abu Hena Mostafa Kamal, in-charge of Rajshahi Medical College Hospital’s Intensive Care Unit, said mother Poly’s body temperature was 101 degrees Fahrenheit on Sunday afternoon.

“She is mentally devastated. That might be the reason for her fever. Her temperature fell slightly after we gave her medicines. We will keep her under observation and release her on Monday if the fever does not increase.”

Manzur was also devastated mentally, but was doing well physically, the hospital authorities said.

The hospital sent blood samples of the couple and Mashia to the IEDCR for Nipah virus tests, but when the results came out negative it urged the Directorate General of Health Services to send a team of experts, said the hospital’s Director Brig Gen AFM Shamim Ahmad.

IEDCR Director Tahmina Shirin said the girls might have caught some other disease. “We’re trying to find out if they were infected by any other virus. More tests are needed. One of our teams has already started for Rajshahi.”