A three-year-old boy died of a brain disease yesterday - the third such fatality revealed since March. The boy, a pupil at Tutor Time International Nursery & Kindergarten in Kowloon Tong, developed a fever and rash over his hands and feet on Thursday, said a spokesman from the Centre for Health Protection. He was admitted to United Christian Hospital in a deteriorating condition on Sunday. He died of encephalitis yesterday, the spokesman said, adding that the boy had had an underlying medical condition. He had tested positive for respiratory syncytial virus (RSV), which causes infections of the lungs and breathing passages. Investigations by the centre showed the boy had not travelled recently. The nursery had not experienced an outbreak of flu or hand, foot and mouth disease, and his family members had no symptoms. 'RSV is a common cause of respiratory tract infection. Common symptoms include fever, chills, headache and decreased appetite,' the spokesman said. Paediatrician Tse Hung-hing said RSV had been common lately, but in most cases it led to pneumonia and bronchitis. He had never heard of the virus causing encephalitis. On March 11, Law Ho-ming, seven, died in Tuen Mun Hospital of flu-related acute necrotising encephalopathy, a similar brain disease. Eleven-year-old Ho Sze-chung died of the brain disease encephalopathy on April 23.