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Haemophilus influenzae type b

Epidemiology of Infectious Diseases: Haemophilus influenzae type b

Causal agent
Haemophilus influenzae serotype b (Hib) is a bacterial infection of young children, which causes meningitis and other bacteraemic diseases including pneumonia, epiglottitis, facial cellulitis and bone and joint infections1.

The most common presentation of invasive Hib disease is meningitis, frequently accompanied by bacteraemia and accounts for an estimated 60% of all cases2.

Common clinical features
Hib meningitis - Symptoms may include progressive headache, stiff neck, drowsiness, intermittent fever and vomiting.

The cases fatality is 3-6%. Hearing impairment or other neurologic sequelae occur in 15-30% of surviving cases.

Epiglottis - an infection and swelling of epiglottis that may cause life-threatening airway obstruction.

Septic arthritis, cellulitis and pneumonia are common manifestations of invasive disease.

Osteomyelitis and pericarditis are less common forms of invasive disease.

Epidemiology
Worldwide, most prevalent in children aged 2 months to 3 years. Uncommon in persons aged over 5 years.
Prior to routine immunisation in the UK, HiB was the second most common cause of bacterial meningitis1.
In 2004 138 cases of Hib were reported in England and Wales (HPA).

Reservoir
Humans 

Mode of transmission
Person to person, transmitted by droplet aerosol or secretions from the nasopharynx of colonized persons.

Incubation period
Unknown, probably 2-4 days.  

Period of Communicability
As long as organisms are present.
Patients are no longer infectious within 24-48 hours of starting appropriate antibiotic treatment.

Prevention and control
Routine vaccination of infants.

References

  1. Heymann D L, editor, Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.
     
  2. Salisbury DM, Begg NT.  Immunisation against infectious disease (The green Book). London: HMSO, 1996. Available at http://www.dh.gov.uk/assetRoot/04/07/29/84/04072984.pdf

© CM Kirwan 2006