Haemophilus influenzae are a species of bacteria that are transmitted from person to person via coughing and sneezing. Haemophilus influenzae type B, or Hib for short, is the best-known type of these bacteria and the one that causes the most diseases. It is mostly found in children under five years of age.
Hib bacteria are part of the body's normal bacterial population (microflora), commonly found in the upper respiratory tracts of many people. Hib infection usually occurs in the setting of other factors, such as additional infections or a weakened immune system.
Most of the trouble caused by Hib, occurs when the bacteria enter the bloodstream and disperse throughout the body. Hib infection can affect many organs and systems, and cause a wide range of problems, including pneumonia and meningitis, which can be potentially fatal.
Despite their confusing name, Hib bacteria do not cause influenza, which is a viral disease.
The Hib vaccine was introduced in the early 1990s, and is now part of the childhood immunization schedule in many countries. Before its introduction, Hib bacteria accounted for nearly half of meningitis cases, especially in infants. After the vaccine was introduced, Hib-related meningitis have rates dropped by about 90% in developed countries. [1]
The most recent estimates are that about 200,000 children under the age of five die every year, worldwide, from Hib-related illnesses, primarily due to low vaccination rates in some developing countries. [2] [3] Hib infections account for 2% of global deaths for this age group. [3]
Jong E.C. Netter F.H and Stevens D.L. (2012) Netter’s Infectious Diseases (1st edition). Philadelphia PA: Elsevier/Saunders.
Estimated Hib and pneumococcal deaths for children under 5 years of age 2008. World Health Organisation. Accessed 11 May 2015 from
Watt J.P. Wolfson L.J. O’Brien K.L. et al. (2009) Burden of disease caused by Haemophilus influenzae type b in children younger than 5 years: global estimates. The Lancet 374:903–911.
Watt J.P. Wolfson L.J. O’Brien K.L. et al. (2009) Burden of disease caused by Haemophilus influenzae type b in children younger than 5 years: global estimates. The Lancet 374:903–911.
Risk factors for Hib infection can include:
A virus transmitted mainly by sexual or blood-to-blood contact, that infects cells of the immune system. It is the causative agent of acquired immune deficiency syndrome (AIDS).
Haemophilus influenzae type B can lead to several types of infections, depending on the organ that it affects. The major conditions that Hib can cause include:
Pneumonia is a lung infection. Each lung is filled with thousands of small airways that branch into tiny air sacs, which allow oxygen from the air we breathe to enter the blood. If you have pneumonia, these air sacs in the lung fill with fluid and mucus, which interferes with this process.
If you have pneumonia you may experience some of these symptoms:
Hib infection was the foremost cause of meningitis in babies and young children before the Hib vaccines were introduced. Today, it is mostly found in unvaccinated people. Meningitis is an inflammation of the meninges, the protective layers surrounding the brain. It is a serious medical emergency that can be life-threatening.
The signs and symptoms of meningitis can closely resemble those of other less serious infective-illnesses such as the flu. They can appear quickly, sometimes hours after infection, or over a few days.
The diagnosis is not always obvious so it is very important to seek professional medical help if you suspect meningitis.
The 'classic' symptoms include:
In infants, the symptoms may appear slightly different. They include:
Pericarditis is an inflammation of the sac surrounding the heart (the pericardium). Symptoms of pericarditis can include:
Cellulitis is infection of the skin. Hib-related cellulitis can show up in infants as bluish-purple spots on the cheeks, around the eye sockets or on the neck. The affected area is tender to the touch. It is usually accompanied by fever.
Hib-related cellulitis can show up bluish spots on the cheeks.
Epiglottitis is inflammation of the epiglottis, the flap of tissue at the base of the tongue, that prevents food and drink from getting into the airways when we eat. An inflamed, swollen epiglottis is a serious condition for infants and young children. The inflammation can develop rapidly and block the airway, leading to breathing difficulties. If severe epiglottitis is not treated immediately, it can cause death.
Arthritis is an inflammation of the joints. Hib infection can lead to arthritis, making joints swollen and tender, and movement painful. Babies with arthritis can be irritable and may not want to be moved or handled.
A connecting surface or tissue between two bones.
A thick, viscous liquid that is secreted for lubrication and to form a protective lining over certain tissues.
A preparation containing a microorganism (that causes a specific disease) in a dead or weakened state, or parts of it, for the purpose of inducing immunity in a person to that microorganism.
If your doctor suspects an Hib infection, they will usually take a body fluid sample (e.g., blood or fluid from around the spinal cord and brain) and test it for the presence of Hib bacteria.
Hib infection is treated with antibiotics. The bacteria are notoriously resistant to penicillin and its derivatives, so other types of antibiotics are often used. Anti-inflammatory medications, such as corticosteroids, can also sometimes be used.
For individuals with epiglottitis, a doctor may decide to insert a breathing tube to help with breathing.
A medication that resembles the cortisol hormone produced in the brain. It is used as an anti-inflammatory medication.
The Hib vaccine is a safe and effective way of preventing Hib infection.
For people who share a living space with a person infected with Hib, antibiotics may be recommended to prevent the infection in the unaffected individuals.
The Hib vaccine is an effective way of preventing a Hib infection.