Haemophilus influenzae Disease: Commonly Asked Questions

Download a PDF version formatted for print: Haemophilus influenzae Disease: Commonly Asked Questions (PDF)

What is Haemophilus influenzae?

Haemophilus influenzae is a bacteria that is found in the nose and throat of children and adults. Some people can carry the bacteria in their bodies but do not become ill.

Haemophilus influenzae serotype B (Hib) is commonly associated with infants and young children and was once the most common cause of severe bacterial infection in children. Due to widespread use of Hib vaccine in children, few cases are reported each year.

Non-serotype B infections occur primarily among the elderly and adults with underlying disease. There are no vaccines available against non-serotype B disease.

What are the symptoms of Haemophilus influenzae?

Haemophilus influenzae causes a variety of illnesses including meningitis (inflammation of the coverings of the spinal column and brain), bacteremia (infection of the blood), pneumonia (infection of the lungs), and septic arthritis (infection of the joints).

Who is at highest risk for Haemophilus influenzae?

Unvaccinated infants and children under age 4 years are at greatest risk for serotype b Hib disease. Additionally, the elderly, adults with underlying disease, and American Indian/Alaskan Native children are at greatest risk of non-serotype B disease. When there is a known case of Hib disease, it is the household contacts, and sometimes the daycare contacts who are at greatest risk.

How is Haemophilus influenzae diagnosed?

Haemophilus influenzae is diagnosed when the bacteria are grown from cultures of the blood, cerebral spinal fluid (CSF) or other normally sterile body site. Cultures take a few days to grow.

How is Haemophilus influenzae infection treated?

Serious infections are treated with specific antibiotics.

Should people who have been in contact with someone diagnosed with Haemophilus influenzae be treated?

For Hib disease, treatment with specific antibiotics is recommended for household members when there is at least one unvaccinated child under 4 years of age in the home. Preventive treatment for non-vaccinated daycare center contacts of known Hib cases may also be recommended.

Is there a vaccine to prevent Haemophilus influenzae infection?

A safe and highly effective vaccine is currently only available for serotype b disease. Infants should be vaccinated against Hib starting at two months of age.

If you have questions about Haemophilus influenzae, please talk with your health care provider.