Haemophilus influenzae are gram-negative bacteria that can cause infection in the respiratory tract, which can spread to other organs.
Infection is spread through sneezing, coughing, or touching.
The bacteria can cause middle ear infections, sinusitis, and more serious infections, including meningitis and epiglottitis, as well as respiratory infections.
Identifying the bacteria in a sample taken from blood or from infected tissue confirms the diagnosis.
Infections are treated with antibiotics given by mouth or, for serious infections, intravenously.
Children are routinely given a vaccine that effectively prevents infections due to Haemophilus influenzae type b.
(See also Overview of Bacteria.)
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 that causes most infections is Haemophilus influenzae.
Haemophilus influenzae can cause infections in children and sometimes in adults.
Risk of getting a Haemophilus influenzae infection is increased in the following:
Children (particularly boys)
Black and Native American people
People who attend or work at a day care center
People who live in overcrowded conditions
People with an immunodeficiency disorder, no spleen, or sickle cell disease
Infection is spread by sneezing, coughing, or touching infected people.
One type, Haemophilus influenzae type b (Hib), is more likely to cause serious infections.
In children, 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 2 severe, often fatal infections:
Meningitis (inflammation of the layers of tissue that cover the brain and spinal cord [meninges] and of the fluid-filled space between the meninges)
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 those with HIV/AIDS.
Symptoms vary depending on the part of the body affected.
Diagnosis of H. influenzae Infections
Tests of a sample of blood or other body fluids
Sometimes examination of a sample of cerebrospinal fluid (obtained by spinal tap)
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. They also can test for genes of 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.
After the bacteria are identified, they may be tested to see which antibiotics are effective (a process called susceptibility testing).
Treatment of H. influenzae Infections
Antibiotics
Haemophilus influenzae infections are treated with antibiotics. Which ones are used depends on the severity and location of the infection and results of susceptibility tests.
If children have a serious Haemophilus influenzae infection, they are hospitalized and kept in isolation to prevent other people from being exposed to infected droplets in the air (called respiratory isolation) for 24 hours after antibiotics are started.
Meningitis
Epiglottitis
Other infections due to Haemophilus influenzaecephalosporins, fluoroquinolones
Prevention of H. influenzae Infections
Children are routinely vaccinated against Haemophilus influenzae type b (see Childhood Vaccination Schedules). The Hib vaccine has greatly reduced the number of serious Haemophilus influenzae type b infections, such as meningitis, epiglottitis, and bacteremia.
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 immunized or is not fully immunized against Haemophilus influenzae
If 2 or more children in a nursery or day care center have Haemophilus influenzae type b infection within a 60-day period, adults and children who were in contact with them should be given an antibiotic.
More Information
The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Centers for Disease Control and Prevention (CDC): Haemophilus influenzae: A resource providing information about Haemophilus influenzae, including how it spreads and vaccination
