Haemophilus are gram-negative bacilli that can cause infections almost anywhere in the body.

Many species of Haemophilus grow in the upper airways of children and adults. Most of these rarely cause disease, but Haemophilus influenzae is a common cause of infection in children and sometimes in adults with chronic lung disease. In children, Haemophilus influenzae can cause infection of the bloodstream, joints, lungs, ears, eyes, sinuses, epiglottis (the area just above the voice box), and the tissues covering the brain and spinal cord (meninges). The symptoms vary depending on the part of the body affected.

Some of the other Haemophilus bacteria cause respiratory tract infections, infections of the heart (endocarditis), and brain abscesses (collections of pus). Haemophilus ducreyi causes chancroid, a sexually transmitted disease (see Sexually Transmitted Diseases (STD): Chancroid).

Haemophilus infections are diagnosed by finding the bacteria in cultures of blood, pus, or other body fluids.

Children are routinely vaccinated against Haemophilus influenzae type b; the vaccine is very effective, especially in preventing meningitis.

Treatment of Haemophilus influenzae meningitis requires intravenous ceftriaxone or cefotaxime. Corticosteroids may help prevent brain damage. Other Haemophilus influenzae infections are treated with a variety of antibiotics, including amoxicillin-clavulanate and trimethoprim-sulfamethoxazole. If the household of a person with a serious Haemophilus influenzae infection has someone younger than 4 years who is not fully immunized against Haemophilus influenzae, all members of the household are given a preventive antibiotic such as rifampin.

Last full review/revision February 2003