Haemophilus influenzae

Haemophilus influenzae is the name of a group of bacteria that can cause mild through to very serious illness, particularly in children under the age of 5 years.

There are 6 different types of haemophilus influenzae bacteria (a through f). They can cause a range of illnesses affecting breathing, joints, bones and the nervous system. Serious cases can sometimes cause lifelong disability or death.

It is possible to carry the bacteria in your nose or throat and not get sick. But sometimes the bacteria gets into the lungs or the bloodstream, and this can lead to serious infections such as meningitis, epiglottis and pneumonia.

Key points


  1. Don’t be confused by its name, haemophilus influenza does not cause influenza (the ‘flu’).
  2. One common type, haemophilus influenza type b (known as Hib) causes 95% of all cases of serious disease. It usually affects children under 5 years old.
  3. Haemophilus influenza bacteria, including Hib, can be spread from one person to another through direct contact or by sneezing and coughing.
  4. It may be necessary for people in close quarters with an infected person to take antibiotics to prevent them from catching the disease.
  5. Fortunately, there is now a vaccine to prevent Hib disease.

Causes

Haemophilus influenza bacteria, including Hib, can be spread from person to person through direct contact or by sneezing and coughing. Many people have the bacteria in their throat and nose but don’t know it, because they do not have any symptoms. This is because normally haemophilus influenza bacteria stay in the nose and throat where they remain harmless. Occasionally the bacteria can get into the blood and spread, leading to serious infection.

The time between exposure and feeling symptoms (incubation period) of haemophilus influenza disease is uncertain, but may be as little as just a few days.

Prevention

Sometimes haemophilus influenza bacteria can infect others who have been in close or long-term contact with a someone who has haemophilus influenza disease. If you are in close contact with someone who has haemophilus influenza disease your doctor may advise you to take antibiotics to prevent you from catching the disease.

Fortunately, there is now a vaccine to prevent Hib disease:

  • Since the introduction of the vaccine in the 1990's, the rate of serious Hib infection has reduced dramatically.
  • We can prevent most cases of Hib infection by making sure all children under 5 years old are vaccinated on time and receive their Hib vaccine. 
  • Unfortunately there are no vaccines currently available for the other types of haemophilus influenza bacteria.

Symptoms

Haemophilus influenza bacteria, including Hib, can cause a range of different infections:

  • Symptoms will vary depending on which part of the body is affected.
  • Symptoms can range from minor ear infections to serious diseases, such as bloodstream infections.
  • Haemophilus influenza bacteria most commonly cause pneumonia (a type of lung infection).

Haemophilus influenza bacteria can also trigger ear infections in children and cause bronchitis in adults.

Invasive disease

When the bacteria infect parts of the body that are usually germ free, e.g. blood or spinal fluid, this is called an "invasive disease" – this tends to be very serious and can sometimes cause death.

The most widespread kinds of invasive haemophilus influenza disease are:

  • Meningitis (infection of the covering of the spinal cord and brain).
  • Epiglottitis (windpipe inflammation; this can lead to trouble breathing).
  • Bacteremia (blood infection).
  • Cellulitis (skin infection).
  • Infectious arthritis.

Before the Hib vaccine, meningitis was the most common kind of invasive haemophilus influenza disease.

Treatment & diagnosis

Diagnosis of invasive haemophilus influenza disease, including Hib, is normally based around a few laboratory tests on a sample of infected body fluid, like spinal fluid or blood.

Haemophilus influenza disease, including Hib disease, is treated using antibiotics, normally for about 10 days.

Invasive disease

  • Nearly all cases of invasive disease (when the bacteria infect parts of the body that are usually germ free e.g. blood or spinal fluid) will need hospitalisation.
  • Even with antibiotics: 3%-6% of children who have the Hib meningitis disease will still die. 

When haemophilus influenza bacteria cause a less serious, non-invasive infection, such as bronchitis or an ear infection, antibiotics might still be prescribed to prevent complications.

Learn more

Haemophilus influenzae type b invasive disease (Hib) Communicable Disease Control Manual 2012 NZ
Haemophilus infections Medline Plus

References

About haemophilus influenzae disease Centers for Disease Control and Prevention, USA

Credits: Health Navigator.