Tarrant County health officials warn of surge in Respiratory Syncytial Virus cases Tarrant County health officials warn of surge in Respiratory Syncytial Virus cases Tarrant County health officials and Cook Children's Hospital are warning of an increase in a respiratory virus that normally peaks in the winter. FORT WORTH, Texas - Tarrant County health officials and Cook Children's Hospital are warning of an increase in a respiratory virus that normally peaks in the winter. Respiratory Syncytial Virus, or RSV, can cause serious health problems for young children. It’s a virus that causes severe breathing difficulty, and it typically shows up between October and January.