Haemophilus influenzae can cause infection in the respiratory tract, which can spread to other organs.
Many species of Haemophilus normally reside in the upper airways of children and adults and rarely cause disease. One species causes chancroid, a sexually transmitted disease. Other species cause infections of heart valves (endocarditis) and, rarely, collections of pus (abscesses) in the brain, lungs, and liver. The species responsible for the most infections is Haemophilus influenzae.
Haemophilus influenzae can cause infections in children and sometimes in adults who have a chronic lung disorder or a weakened immune system. Infection is spread by sneezing, coughing, or touching infected people. One type of Haemophilus influenzae, called type b, is more likely to cause serious infections.
In children, Haemophilus influenzae type b (Hib) can spread through the bloodstream (causing bacteremia) and infect the joints, bones, lungs, skin of the face and neck, eyes, urinary tract, and other organs. The bacteria may cause two severe, often fatal infections: meningitis and epiglottitis (infection of the flap of tissue over the voice box). Some strains cause infection of the middle ear in children, the sinuses in children and adults, and the lungs in adults, especially those with chronic obstructive pulmonary disease (COPD) or AIDS.
Symptoms and Diagnosis
Symptoms vary depending on the part of the body affected.
To diagnose the infection, doctors take a sample of blood, pus, or other body fluids and send it to a laboratory to grow (culture) the bacteria. If people have symptoms of meningitis, doctors do a spinal tap (lumbar puncture) to obtain a sample of the fluid that surrounds the brain and spinal cord (cerebrospinal fluid). Identifying the bacteria in a sample confirms the diagnosis.
Prevention and Treatment
Children are routinely vaccinated against Haemophilus influenzae type b. The vaccine is very effective, especially in preventing meningitis, epiglottitis, and bacteremia.
Treatment of meningitis must begin as soon as possible. An antibiotic—usually, ceftriaxone or cefotaxime—is given intravenously. Corticosteroids may help prevent brain damage.
Epiglottitis must also be treated as soon as possible. People may need help breathing. An artificial airway, such as a breathing tube, may be inserted, or rarely, an opening may be made in the windpipe (a procedure called tracheostomy). The antibiotic rifampin is used because it can eradicate the bacteria from the throat. People are given this antibiotic before they are discharged from the hospital.
If the household of a person with a serious Haemophilus influenzae type b infection includes a child who is under 4 years old and is not fully immunized against Haemophilus influenzae type b, the child should be vaccinated. Also, all members of the household, except pregnant women, should be given an antibiotic, such as rifampin, by mouth to prevent infection.
Other Haemophilus influenzae infections are treated with various antibiotics given by mouth. They include amoxicillin-clavulanate, azithromycin, cephalosporins, clarithromycin, fluoroquinolones, and trimethoprim-sulfamethoxazole.
Last full review/revision September 2008 by Matthew E. Levison, MD