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.
Children are routinely given a vaccine that effectively prevents infections due to Haemophilus influenzae type b.
Infections are treated with antibiotics given by mouth or, for serious infections, intravenously.
(See also Overview of Bacteria Overview of Bacteria Bacteria are microscopic, single-celled organisms. They are among the earliest known life forms on earth. There are thousands of different kinds of bacteria, and they live in every conceivable... read more .)
Many species of Haemophilus normally reside in the upper airways of children and adults and rarely cause disease. One species causes chancroid Chancroid Chancroid is a sexually transmitted infection caused by the bacteria Haemophilus ducreyi, which causes painful genital sores. Chancroid is a sexually transmitted infection (STI) that... read more , a sexually transmitted disease. Other species cause infections of heart valves (endocarditis Infective Endocarditis Infective endocarditis is an infection of the lining of the heart (endocardium) and usually also of the heart valves. Infective endocarditis occurs when bacteria enter the bloodstream and travel... read more 
) 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.
Risk of getting a Haemophilus influenzae infection is increased in the following:
Children (particularly boys)
Black people
Native Americans
People who attend or work at a day care center
People who live in overcrowded conditions
People with an immunodeficiency disorder Overview of Immunodeficiency Disorders Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more , no spleen Overview of the Spleen The spleen, a spongy, soft organ about as big as a person’s fist, is located in the upper left part of the abdomen, just under the rib cage. The splenic artery brings blood to the spleen from... read more , or sickle cell disease Sickle Cell Disease Sickle cell disease is an inherited genetic abnormality of hemoglobin (the oxygen-carrying protein found in red blood cells) characterized by sickle (crescent)-shaped red blood cells and chronic... read more
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 Bacteremia Bacteremia is the presence of bacteria in the bloodstream. Bacteremia may result from ordinary activities (such as vigorous toothbrushing), dental or medical procedures, or from infections ... read more ) 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:
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 Chronic Obstructive Pulmonary Disease (COPD) Chronic obstructive pulmonary disease is persistent narrowing (blocking, or obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders. Cigarette... read more 
(COPD) or AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and is treated with antiretroviral medications. If untreated, it can cause... read more 
.
Symptoms vary depending on the part of the body affected.
Diagnosis of H. influenzae Infections
Culture 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. If people have symptoms of meningitis, doctors do a spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more 
(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 Testing a Microorganism's Susceptibility and Sensitivity to Antimicrobial Drugs Infectious diseases are caused by microorganisms, such as bacteria, viruses, fungi, and parasites. Doctors suspect an infection based on the person's symptoms, physical examination results,... read more ).
Prevention of H. influenzae Infections
Children are routinely vaccinated against Haemophilus influenzae type b ( see Table: Childhood Vaccination Schedules Childhood Vaccination Schedules Vaccination protects children against many infectious diseases. Vaccines contain either noninfectious components of bacteria or viruses or whole forms of these organisms that have been weakened... read more ). The vaccine Haemophilus influenzae Type b Vaccine The Haemophilus influenzae type b (Hib) vaccine helps protect against bacterial infections due to Hib, such as pneumonia and meningitis. These infections may be serious in children. Use... read more 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 fully immunized against Haemophilus influenzae type b, the child should be vaccinated. Also, all members of the household, except pregnant women, should be given the antibiotic rifampin to prevent infection.
If two 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.
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 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 must be treated 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). An antibiotic, such as ceftriaxone, cefotaxime, or cefuroxime, is given.
Other infections due to Haemophilus influenzae are treated with various antibiotics given by mouth. They include amoxicillin/clavulanate, azithromycin, cephalosporins Cephalosporins Cephalosporins are a subclass of antibiotics called beta-lactam antibiotics (antibiotics that have a chemical structure called a beta-lactam ring). Beta-lactam antibiotics also include carbapenems... read more , fluoroquinolones Fluoroquinolones Fluoroquinolones are a class of broad-spectrum antibiotics that are used to treat a variety of infections. Fluoroquinolones include the following: Ciprofloxacin Delafloxacin Gemifloxacin read more , omadacycline, lefamulin, and clarithromycin.
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
