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Description of Haemophilus Influenzae

Haemophilus influenzae type b, better known as Hib, is a bacterium responsible for roughly 3 million serious illnesses worldwide each year. The World Health Organization (WHO) estimates that nearly 400,000 people die each year of Hib-related illnesses, the most deadly of which are meningitis and pneumonia. Invasive diseases caused by this bacterium are often lumped together and referred to collectively as Hib disease.

  1. Hib-Related Illnesses

    • The U.S. Centers for Disease Control and Prevention (CDC) lists ten invasive diseases that can be caused by Hib. These include the aforementioned meningitis and pneumonia, as well as cellulitis, endocarditis, osteomyelitis, epiglottitis, occult febrile bacteremia, septic arthritis, purulent pericarditis and otitis media.

    Incidence

    • The CDC reports that the incidence of Hib-related illnesses in the United States is quite low and has been down sharply since the early 1990s. The inclusion of Hib conjugate vaccine in the series of immunizations routinely administered to American children is responsible for this sharp decline. The current rate of incidence among American children is 1 case for every 100,000 children under the age of 5, according to the CDC. The rate of Hib infection is far higher in developing countries where Hib vaccine is not routinely available.

    How It Spreads

    • The Hib bacterium is found in the nasopharyngeal passages (nose and throat) of people suffering from the effects of a Hib-related illness and of many healthy individuals as well. It can spread to others through exhaled droplets containing the bacterium or through other means of close contact with Hib-infected patients or asymptomatic carriers.

    Complications

    • The potential damage from Hib infections, according to the WHO, is greatest when the infection invades the bloodstream and spreads to other parts of the body. Two of the areas most vulnerable to attack are the meninges, the membranes covering the brain and spinal cord, and the lungs. Hib infection of the former results in Hib-related meningitis, while infection of the lungs leads to pneumonia. The WHO points out, however, that both meningitis and pneumonia also can be caused by a number of other infectious agents. To conclusively pinpoint Hib as the causative bacterium, fluid from the spinal column or from the lungs of infected patients must be analyzed for the presence of Hib.

    Treatment of Hib Infections

    • Hib infections generally respond well to treatment such as antibiotics if treatment begins before the infection has become too advanced, according to the Hib Initiative. This is particularly true of meningitis, which can cause permanent neurologic damage if treatment is not initiated in the very early stages of infection. In rare cases, antibiotic-resistant strains of the Hib bacterium are encountered, making treatment difficult or impossible.

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