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Causes and Transmission

Haemophilus influenzae bacteria, including Hib, are spread person-to-person by direct contact or through respiratory droplets like by coughing and sneezing.

Haemophilus influenzae disease, including Hib disease, is caused by the bacterium Haemophilus influenzae. There are six identifiable types of Haemophilus influenzae bacteria (a through f) and other non-identifiable types (called nontypeable). The one that most people are familiar with is Haemophilus influenzae type b, or Hib.

Haemophilus influenzae bacteria, including Hib, are spread person-to-person by direct contact or through respiratory droplets like by coughing and sneezing. Usually the bacteria remain in the nose and throat — causing no harm. Sometimes the bacteria can enter the blood and spread, causing serious infection in the individual. Most of the time, Haemophilus influenzae bacteria are spread by people who have the bacteria in their noses and throats but who are not ill (asymptomatic). The incubation period (time between exposure and first symptoms) of Haemophilus influenzae disease is not certain, but could be as short as a few days.

Sometimes Haemophilus influenzae bacteria spread to other people who have had close or lengthy contact with a patient with Haemophilus influenzae disease. In certain cases, people in close contact with that patient should receive antibiotics to prevent them from getting the disease. Learn more about antibiotic prophylaxis.

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