Meningitis - H. influenzae

Meningitis - H. influenzae

Definition:

Haemophilus influenzae meningitis is an infection of the membranes covering the brain and spinal cord (meninges) caused by H. influenzae bacteria.

Alternative Names:

H. influenzae meningitis; H. flu meningitis

Causes, incidence, and risk factors:

Haemophilus influenzae type B (Hib) is a type of bacteria, not to be confused with the disease influenza, a lung infection caused by a virus.

Prior to the availability of the Hib immunization, H. influenzae was the leading cause of bacterial meningitis in children under 5 years of age. It occurs most frequently in children from 1 month up to 4 years with a peak at 6 to 9 months.

Routine Hib immunization has resulted in a marked decrease in the incidence of H. influenzae meningitis. H. influenzae meningitis may follow an upper respiratory infection and may develop slowly or rapidly. The infection usually spreads from somewhere in the respiratory tract to the bloodstream and then to the meninges (the membranes that cover the brain). At the meninges, the bacteria produce infection and inflammation causing serious illness and sometimes death.

Since the introduction of the vaccine, H. influenzae now occurs in less than 2 in 100,000 children.

Risk factors include a recent history of otitis media (ear infection), sinusitis (infection of sinuses), pharyngitis (sore throat), or other upper respiratory infection or a history of a family members with an H. influenzae infection. Another significant risk factor includes race -- Native Americans and Eskimos have a rate of more than 3 times that of the general population. Placement in day care also increases risk.

Symptoms:

Irritability,poor feeding in infants
Fever (in young infants the temperature may actually be below normal)
Severe headache (older children)
Nausea and vomiting
Stiff neck or pain in neck when flexed
Pain in back when neck is flexed foreward and chin brought toward chest (older children)
Unusual body posturing
Sensitivity to light

Signs and tests:

Bulging of the fontanelles ("soft spots") in infants
Opisthotonos (lying with the back arched, head, back, and chin up)
Seizures
Poor circulation
Mental status changes (irritability, stupor, coma)
Elevated white blood cell count in blood
Spinal fluid shows increased number of white blood cells
Spinal fluid culture showing bacteria
Serology (antibodies in blood) showing recent exposure to H. influenzae
Blood culture growing H. influenzae

Treatment:

Treatment of meningitis must be started as soon as the diagnosis is suspected. H. influenzae meningitis should be treated with antibiotics. Steroid medication may also be used, mostly in children. Steroids are given to reduce hearing loss, which is a common complication of meningitis.

Expectations (prognosis):

The probable outcome is good with early treatment. However, 3-5% of patients do not survive.

Complications:

Roughly 20% of patients may experience some hearing loss. Some patients will have brain damage, which can include seizures, mental retardation, hydrocephalus ("water on the brain"), learning disorders, abnormalities in speech and language development, and behavioral problems.

Calling your health care provider:

If you experience any of the symptoms of H. influenzae or if you notice these symptoms in your child, contact your health care provider or go to an emergency room. Meningitis can quickly become life-threatening.

Prevention:

For protection of the general public (infant and early childhood):

Several types of Hib vaccine are available for children that are at least 2 months old.
Hib immunizations for infants and children are recommended by the American Academy of Pediatrics, the National Institutes of Health, and many other health agencies.

For prevention following exposure to known cases of H. influenzae meningitis or infection:

It is recommended that all family contacts of individuals with this type of meningitis who are not immunized begin chemoprophylaxis (drug therapy for prevention) as soon as possible.
Ask your health care provider about this treatment during the initial diagnostic visit.

Review Date: 7/31/2002
Reviewed By: Christopher Parsons, M.D., Department of Internal Medicine, Division of Infectious Diseases, University of Virginia, Charlottesville, VA. Review provided by VeriMed Healthcare Network.

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