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Haemophilus influenzae meningitis is a bacterial infection of the membranes covering the brain and spinal cord (meninges).

See also:

• Aseptic meningitis
• Meningitis
• Meningitis - cryptococcal
• Meningitis - gram-negative
• Meningitis - meningococcal
• Meningitis - pneumococcal
• Meningitis - staphylococcal
• Meningitis - tuberculous

H. influenzae meningitis is caused by Haemophilus influenzae bacteria. This bacteria should not be confused with the disease influenza, an upper respiratory infection caused by the influenza virus.

Before the Hib vaccine became available, H. influenzae was the leading cause of bacterial meningitis in children under 5 years of age. Since the introduction of the vaccine in the U.S., H. influenzae now occurs in less than 2 in 100,000 children. It still causes 5% - 10% of bacterial meningitis cases in adults.

H. influenzae meningitis may come after an upper respiratory infection. The infection usually spreads from the respiratory tract to the bloodstream, and then to the meninges. At the meninges, the bacteria produce infection and inflammation, causing serious illness and sometimes death.

Risk factors include:

• Ear infection (otitis media)
• Family member with an H. influenzae infection
• Native American race
• Placement in day care
• Sinus infection (sinusitis)
• Sore throat (pharyngitis)
• Upper respiratory infection

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

Signs include:

• Bulging of the fontanelles in an infant
• Lying with the back arched, head, back, and chin up (opisthotonos)
• Mental status changes (such as irritability, reduced consciousness, coma)
• Poor blood flow (circulation)
• Seizures

For any patient with meningitis, it is important to perform a lumbar puncture ("spinal tap"), in which spinal fluid (known as cerebrospinal fluid, or CSF) is collected for testing.

Other tests include:

• Antibodies in blood (serology)
• Blood culture
• Spinal fluid culture
• White blood cell count

Treatment must be started as soon as meningitis is suspected. H. influenzae meningitis should be treated with antibiotics given through a vein (IV).

Steroid medication may also be used, mostly in children. Steroids are given to reduce hearing loss, which is a common complication of meningitis in children.

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

• Abnormal speech and language development
• Behavioral problems
• Hearing loss
• Hydrocephalus
• Learning disorders
• Mental retardation
• Seizures

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

To protect infants and young children:

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

To prevent infection after being exposed to H. influenzae meningitis:

• All family contacts of people with this type of meningitis who have not been vaccinated should begin drug therapy to prevent infection as soon as possible.
• Ask your health care provider about this treatment during the first visit.

H. influenzae meningitis; H. flu meningitis

Swartz MN. Meningitis: bacterial, viral, and other. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 437.

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Jatin M. Vyas, PhD, MD, Instructor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.