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H influenzae meningitis

Definition

Meningitis is an infection of the membranes covering the brain and spinal cord. This covering is called the meninges.

Bacteria are one type of germ that can cause meningitis. Haemophilus influenzae type b is one kind of bacteria that causes meningitis.

Meninges of the brain
The organs of the central nervous system (brain and spinal cord) are covered by connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.

Alternative Names

H. influenzae meningitis; H. flu meningitis; Haemophilus influenzae type b meningitis

Causes

H influenzae meningitis is caused by Haemophilus influenzae type b bacteria. This illness is not the same as the flu (influenza), which is caused by a virus.

Before the Hib vaccine, H influenzae was the leading cause of bacterial meningitis in children under age 5. Since the vaccine became available in the United States, this type of meningitis occurs much less often in children in the United States.

H influenzae meningitis may occur after an upper respiratory infection. The infection usually spreads from the lungs and airways to the blood, then to the brain area.

Risk factors include:

  • Attending day care
  • Cancer
  • Ear infection (otitis media) with H influenzae infection
  • Family member with an H influenzae infection
  • Native American race
  • Pregnancy
  • Older age
  • Sinus infection (sinusitis)
  • Sore throat (pharyngitis)
  • Upper respiratory infection
  • Weakened immune system

Symptoms

Symptoms usually come on quickly, and may include:

Other symptoms that can occur include:

Exams and Tests

The health care provider will perform a physical exam. Questions will focus on symptoms and possible exposure to someone who might have the same symptoms, such as a stiff neck and fever.

If the doctor thinks meningitis is possible, a lumbar puncture (spinal tap) is done to take a sample of spinal fluid for testing.

Other tests that may be done include:

  • Blood culture
  • Chest x-ray
  • CT scan of the head
  • Gram stain or other special stains, and culture of the spinal fluid
CSF cell count
CSF (cerebrospinal fluid) is a clear fluid that circulates in the space surrounding the spinal cord and brain. A CSF cell count is a test to measure the number of red and white blood cells that are in CSF.

Treatment

Antibiotics will be given as soon as possible. Ceftriaxone is one of the most commonly used antibiotics. Ampicillin may sometimes be used.

Corticosteroids may be used to fight inflammation.

Unvaccinated people who are in close contact with someone who has H influenzae meningitis should be given antibiotics to prevent infection. Such people include:

  • Household members
  • Roommates in dormitories
  • Those who come into close contact with an infected person

Outlook (Prognosis)

Meningitis is a dangerous infection and it can be deadly. The sooner it is treated, the better the chance for recovery. Young children and adults over age 50 have the highest risk for death.

Possible Complications

Long-term complications may include:

When to Contact a Medical Professional

Call 911 or the local emergency number or go to an emergency room if you suspect meningitis in a young child who has the following symptoms:

  • Feeding problems
  • High-pitched cry
  • Irritability
  • Persistent, unexplained fever

Meningitis can quickly become a life-threatening illness.

Prevention

Infants and young children can be protected with the Hib vaccine.

Close contacts in the same household, school, or day care center should be watched for early signs of the disease as soon as the first person is diagnosed. All unvaccinated family members and close contacts of this person should begin antibiotic treatment as soon as possible to prevent spread of the infection. Ask your provider about antibiotics during the first visit.

Always use good hygiene habits, such as washing hands before and after changing a diaper, and after using the bathroom.

Gallery

Meninges of the brain
The organs of the central nervous system (brain and spinal cord) are covered by connective tissue layers collectively called the meninges. Consisting of the pia mater (closest to the CNS structures), the arachnoid and the dura mater (farthest from the CNS), the meninges also support blood vessels and contain cerebrospinal fluid. These are the structures involved in meningitis, an inflammation of the meninges, which, if severe, may become encephalitis, an inflammation of the brain.
Brudzinski's sign of meningitis
One of the physically demonstrable symptoms of meningitis is Brudzinski's sign. Severe neck stiffness causes a patient's hips and knees to flex when the neck is flexed.
Central nervous system and peripheral nervous system
The central nervous system comprises the brain and spinal cord. The peripheral nervous system includes all peripheral nerves.
CSF cell count
CSF (cerebrospinal fluid) is a clear fluid that circulates in the space surrounding the spinal cord and brain. A CSF cell count is a test to measure the number of red and white blood cells that are in CSF.
Periorbital cellulitis
Periorbital cellulitis is an acute infection of the tissues surrounding the eye, which may progress to orbital cellulitis with protrusion of the eyeball. Complications include meningitis.

References

Centers for Disease Control and Prevention website. Bacterial meningitis. www.cdc.gov/meningitis/bacterial.html. Reviewed July 15, 2021. Accessed November 10, 2022.

Nath A. Meningitis: bacterial, viral, and other. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 384.

Hasbun R, Van de Beek D, Brouwer MC, Tunkel AR. Acute meningitis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 87.

Last reviewed September 10, 2022 by Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team..

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