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.

Mosquito, adult feeding on the skin — There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)

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:

Fever and chills
Mental status changes
Nausea and vomiting
Sensitivity to light (photophobia)
Severe headache
Stiff neck (meningismus)

Other symptoms that can occur include:

Agitation
Bulging fontanelles in infants
Decreased consciousness
Poor feeding and irritability in children
Rapid breathing
Unusual posture, with the head and neck arched backwards (opisthotonos)

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 (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:

Brain damage
Buildup of fluid between the skull and brain (subdural effusion)
Buildup of fluid inside the skull that leads to brain swelling (hydrocephalus)
Hearing loss
Seizures

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

Central nervous system and peripheral nervous system — There are many different species of mosquito, which can carry some of the world's most common and significant infectious diseases, including West Nile, Malaria, yellow fever, viral encephalitis, and dengue fever. (Image courtesy of the Centers for Disease Control and Prevention.)

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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