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Meningitis

Meningitis is an inflammation of the membranes that cover the brain and spinal cord. People sometimes refer to it as spinal meningitis.

Causes

Meningitis is mostly caused by microorganisms like bacteria, viruses, parasites, and fungi. These microorganisms infect blood and the cerebrospinal fluid (CSF). Meningitis can also develop from non-infectious causes, including certain diseases like AIDS, cancer, diabetes, physical injury, or certain drugs that weaken the body’s immune system.

Bacterial Meningitis

Bacterial meningitis is usually more severe than viral meningitis. Bacterial meningitis can have serious after-effects, such as brain damage, hearing loss, limb amputation, or learning disabilities.

One of the leading causes of bacterial meningitis in children and young adults in the United States is the bacterium Neisseria meningitidis. Meningitis caused by this bacterium is known as meningococcal disease. Other age groups are caused by different bacteria.

Viral Meningitis

Viral meningitis is generally less severe and resolves without specific treatment.

Most viral meningitis cases in the United States, especially during the summer months, are caused by enteroviruses; however, only a small number of people with enterovirus infections actually develop meningitis.

Other viral infections that can lead to meningitis include

  • Mumps
  • Herpesvirus, including Epstein-Barr virus, herpes simplex viruses, varicella-zoster virus (which also causes chicken pox and shingles), measles, and influenza
  • Viruses spread through mosquitoes and other insects (arboviruses)
  • In rare cases LCMV (lymphocytic choriomeningitis virus), which is spread by rodents, can cause viral meningitis
Fungal Meningitis

Fungal meningitis is rare, but can be life threatening. Although anyone can get fungal meningitis, people at higher risk include those who have AIDS, leukemia, or other forms of immunodeficiency (an immune system that does not respond adequately to infections) and immunosuppression (immune system malfunction as a result of medical treatment).

The most common cause of fungal meningitis for people with immune system deficiencies, like HIV, is Cryptococcus. This disease is one of the most common causes of meningitis in Africa.

Non-infectious Meningitis

Non–infectious meningitis causes include

  • Cancers
  • Systemic lupus erythematosus (lupus)
  • Certain drugs
  • Head injury
  • Brain surgery

Transmission

Bacterial Meningitis

Bacterial meningitis is contagious. The bacteria are spread through the exchange of respiratory and throat secretions (i.e., coughing, kissing). Fortunately, none of the bacteria that cause meningitis are as contagious as things like the common cold or the flu. Also, the bacteria are not spread by casual contact or by simply breathing the air where a person with meningitis has been.

Sometimes the bacteria that cause meningitis have spread to other people who have had close or prolonged contact with a patient with meningitis caused by N. meningitidis (also called meningococcal meningitis) or H. influenzae serotype b (also called Hib meningitis).

People in the same household or daycare center or anyone with direct contact with a patient's oral secretions (such as a boyfriend or girlfriend) would be considered at increased risk of getting the infection. People who qualify as close contacts of a person with meningitis caused by N. meningitidis should receive antibiotics to prevent them from getting the disease.

Viral Meningitis

Enteroviruses, the most common cause of viral meningitis, are most often spread from person to person through fecal contamination (which can occur when changing a diaper or using the toilet and not properly washing hands afterwards). Enteroviruses can also be spread through respiratory secretions (saliva, sputum, or nasal mucus) of an infected person. Other viruses, such as mumps and varicella-zoster virus, may also be spread through direct or indirect contact with saliva, sputum, or mucus of an infected person. Contact with an infected person may increase your chance of becoming infected with the virus that made them sick; however you will have a small chance of developing meningitis as a complication of the illness.

Fungal Meningitis

Fungal meningitis is not contagious. It is not transmitted from person to person. People at risk for fungal meningitis acquire the infection usually by inhaling fungal spores from the environment. People with certain medical conditions like diabetes, cancer, or HIV are at higher risk of fungal meningitis. You may also get fungal meningitis after taking medications that suppress your immune system. Examples of these medications include steroids (such as prednisone), medications given after organ transplantation, or anti-TNF medications, which are sometimes given for treatment of rheumatoid arthritis or other autoimmune conditions.

Cryptococcus is felt to be acquired through inhaling soil contaminated with bird droppings, and Histoplasma is found in environments with heavy contamination of bird or bat droppings, particularly in the Midwest near the Ohio and Mississippi Rivers. The Midwest United States, particularly the northern Midwest, is endemic to the fungus Blastomyces. This fungus is thought to exist in soil rich in decaying organic matter. Coccidioides is found in the soil of endemic areas (Southwestern US and parts of Central and South America). When these environments are disturbed, the fungal spores can be inhaled. Meningitis results from the fungal infection spreading to the spinal cord.

Symptoms

Meningitis infection is characterized by a sudden onset of fever, headache, and stiff neck. It is often accompanied by other symptoms, such as

  • Nausea
  • Vomiting
  • Photophobia (sensitivity to light)
  • Altered mental status
Bacterial Meningitis

The symptoms of bacterial meningitis can appear quickly or over several days. Typically they develop within 3-7 days after exposure.

Infants younger than one month old are at a higher risk for severe infection. In newborns and infants, the classic symptoms of fever, headache, and neck stiffness may be absent or difficult to notice. The infant may appear to be slow or inactive, irritable, vomiting or feeding poorly. In young children, doctors may also look at the child’s reflexes, which can also be a sign of meningitis.

Although the early symptoms of viral meningitis and bacterial meningitis may be similar, later symptoms of bacterial meningitis can be very severe (e.g., seizures, coma). For this reason, if you think you or someone else may have meningitis, see a physician as soon as possible.

Viral Meningitis

Viral meningitis is an infection of the meninges (the covering of the brain and spinal cord) that is caused by a virus. Enteroviruses, the most common cause of viral meningitis, appear most often during the summer and fall in temperate climates.

Viral meningitis can affect babies, children, and adults. It is usually less severe than bacterial meningitis and normally clears up without specific treatment. The symptoms of viral meningitis are similar to those for bacterial meningitis, which can be fatal. Because of this, it is important to see a healthcare provider right away if you think you or your child might have meningitis.

Symptoms of viral meningitis in adults may differ from those in children:

Common symptoms in infants

  • Fever
  • Irritability
  • Poor eating
  • Hard to awaken

Common symptoms in adults

  • High fever
  • Severe headache
  • Stiff neck
  • Sensitivity to bright light
  • Sleepiness or trouble waking up
  • Nausea, vomiting
  • Lack of appetite

The symptoms of viral meningitis usually last from 7 to 10 days, and people with normal immune systems usually recover completely.

Fungal Meningitis

Symptoms of fungal meningitis are similar to symptoms of other forms of meningitis; however, they often appear more gradually. In addition to typical meningitis symptoms, like headache, fever, nausea, and stiffness of the neck, people with fungal meningitis may also experience:

  • Dislike of bright lights
  • Changes in mental status, confusion
  • Hallucinations
  • Personality changes

Diagnosis

Early diagnosis and treatment are very important. Classic signs of meningitis include sudden onset of fever, headache and stiff neck. These signs are often accompanied by other symptoms, such as nausea, vomiting, sensitivity to light (photophobia), and altered mental status. Older children and adults may experience a skin rash. In young children, the signs may be more subtle and my include inactivity, irritability, vomiting, or poor feeding.

If meningitis is suspected, samples of blood or cerebrospinal fluid are collected and sent to the laboratory for testing. It is important to know the specific cause of meningitis because the severity of illness and the treatment will differ depending on the cause. In the case of bacterial meningitis, for example, antibiotics can help prevent severe illness and reduce the spread of infection from person to person.

Bacterial Meningitis

If bacteria are present, they can be grown (cultured). Growing the bacteria in the laboratory is important for confirming the presence of bacteria and for identifying the specific type of bacteria that is causing the infection.

Viral Meningitis

The specific causes of meningitis may be determined by tests used to identify the virus in samples collected from the patient.

Fungal Meningitis

To confirm fungal meningitis, specific lab tests can be performed, depending on the type of fungus suspected.

Treatment

Bacterial Meningitis

Bacterial meningitis can be treated with a number of effective antibiotics. It is important that treatment be started early in the course of the disease. If bacterial meningitis is suspected, initial treatment with ceftriaxone and vancomycin is recommended. Appropriate antibiotic treatment of the most common types of bacterial meningitis should reduce the risk of dying from meningitis to below 15%, although the risk is higher among the elderly.

Viral Meningitis

There is no specific treatment for viral meningitis. Antibiotics do not help viral infections, so they are not useful in the treatment of viral meningitis. Most patients completely recover on their own within 7 to 10 days. A hospital stay may be necessary in more severe cases or for people with weak immune systems.

Fungal Meningitis

Fungal meningitis is treated with long courses of high dose antifungal medications. This is usually given using an IV line and is done in the hospital. The length of treatment depends on the status of the immune system and the type of fungus that caused the infection. For people with immune systems that do not function well because of other conditions, like AIDS, diabetes, or cancer, there is often a need for longer treatment.

Vaccines

There are vaccines for three bacteria that can cause meningitis: Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae type b (Hib). No vaccines are available for the most common causes of viral meningitis.

 

Source

Centers for Disease Control and Prevention, USA.