Haemophilus influenzae is a type of bacterium that grows in the upper airways of adults and children, normally without causing any disease. Haemophilus influenzae type b, known as Hib for short, is one of 6 types that have been described.
Haemophilus influenzae type b can cause some serious life-threatening conditions, including meningitis (inflammation of the lining of the brain and spinal cord) and epiglottitis (inflammation of the epiglottis — the small cartilage at the base of your tongue that closes off your voice box when you eat or drink). Since widespread vaccination, however, Hib is not a common cause of either of these conditions.
Other conditions that Hib can cause are pneumonia, septic arthritis, bronchitis and middle ear infections.
How is Haemophilus influenzae spread?
Haemophilus influenza type B (Hib) is highly contagious, spread by infected droplets of fluid dispersed when infected people cough or sneeze. Hib can be spread by healthy people who may carry the bacteria in their nose and throat. Hib can also be spread by direct contact with the infected droplets on surfaces, but it does not survive long outside of the body.
What problems and complications can Hib cause?
Haemophilus influenzae infection can cause several serious diseases, and invasive infection will always require immediate hospitalisation for the infected person. The diseases that Hib infection can cause include:
- Meningitis – infection of the spinal cord and brain
- Epiglottitis – inflammation of the epiglottis — the small cartilage at the base of your tongue that closes off your voice box when you eat or drink
- Middle ear infections
- Conjunctivitis – inflammation of the conjunctiva – the clear tissue that lines the eyelids and the white part of the eyeball
- Sinusitis – inflammation of the sinuses
- Bronchitis – inflammation of the air passages of the lungs
- Pneumonia – inflammation of the lungs
- Septic arthritis – infection of a joint(s)
- Septicaemia – blood poisoning.
Symptoms of Hib
The incubation period of Hib is thought to be 2-4 days. Nowadays, most cases in Australia are not in children, but in adults who have long-term underlying medical conditions.
Symptoms of Hib infection depend on what problems or conditions it is causing and can include:
- Signs and symptoms of meningitis, such as a stiff neck and photophobia (sensitivity to light). These are rare in infants, who have more non-specific symptoms such as high fever, drowsiness and poor feeding.
- Signs and symptoms of epiglottitis, such as breathing difficulties, anxiety, dribbling/drooling, and stridor (a high pitched breathing sound).
- Fever and chills.
- Tiredness – excessive.
- Difficulty breathing or shortness of breath.
Symptoms can appear quickly and worsen quickly in children, so urgent medical attention is necessary.
Diagnosis of Hib infection will usually depend on isolating and identifying the Haemophilus bacteria. If a doctor suspects you have Hib infection, they will take a blood sample. You may need to have a lumbar puncture to give a CSF (cerebrospinal fluid) sample. Other investigations that may be carried out to help with diagnosis include a chest X-ray, a CT scan or ECG (echocardiogram).
Invasive Hib infection is a notifiable disease in Australia.
Treatment for Hib will usually involve antibiotics and for invasive disease, urgent admission to hospital. Depending on the symptoms a person may need other measures, e.g. oxygen therapy to help with breathing.
Outlook after Hib infection
Aside from the risk of death, there may be also be long-lasting effects resulting from Hib meningitis. These can include nerve problems, permanent hearing loss and convulsions. Septic arthritis could cause damage to joints, but most other Hib infections are more likely to resolve without long term consequences.
Vaccination against Haemophilus influenzae
Vaccination is the best way to avoid Hib infection. Since the introduction of routine vaccination against Hib in 1993 in Australia, the number of cases of Hib infection has been greatly reduced. In the years before vaccination was brought in, there were usually at least 500 cases of Hib every year in children under 6 in Australia.
Aboriginal and Torres Strait Islander children had a higher incidence of Hib disease than non-indigenous children and tended to have Hib disease at a younger age, however, there has been a marked reduction in infections since vaccination was introduced.
Hib vaccination is available on the National Immunisation Program for free. Current recommendations are for vaccination of all children from 2 months of age, along with the other standard childhood vaccines.
Hib injections are given at different ages, depending on the type of Hib vaccine used. Hib vaccine is given in conjunction with other vaccines at:
- 2 months, 4 months and 6 months, with a booster at 12 months, or
- 2 months, 4 months and 12 months.
Catch-up vaccination is available for children under 5 years of age, who have missed having Hib vaccination. See your doctor if you have children under 5 who are not protected against Hib.