What causes bronchiolitis?

What causes bronchiolitis?

The viruses that cause most cases of bronchiolitis are the respiratory syncytial virus (RSV), the rhinovirus and the influenza (flu) virus. These viruses are very contagious and are spread from person to person by touching secretions from the mouth or nose or by respiratory droplets in the air. The droplets get into the air when someone sneezes or coughs.