Haemophilus influenza bacteria are spread through respiratory droplets and through person-to-person contact.
The contagious period varies and, unless treated, can last for as long as the bacteria are present in the nose and throat, even after symptoms have disappeared. A person can no longer spread Hib disease after taking antibiotics for one to two days.
Until recently, Hib was one of the most common cause of bacterial infection in young children. Since an effective vaccine has been available, very few cases of Hib disease are now diagnosed.