What is meningitis?
Meningitis is an infection of the membranes (meninges) surrounding the brain and spinal cord. Meningitis can be caused by a bacterial, fungal or viral infection. Meningitis can be acute, with a quick onset of symptoms, it can be chronic, lasting a month or more, or it can be mild or aseptic. Anyone experiencing symptoms of meningitis should see a doctor immediately.
What is bacterial meningitis?
Acute bacterial meningitis is the most common form of meningitis. Approximately 80% of all cases are acute bacterial meningitis. Bacterial meningitis can be life threatening. The infection can cause the tissues around the brain to swell. This in turn interferes with blood flow and can result in paralysis or even stroke.
Bacterial meningitis is very serious and can be deadly. Death can occur in as little as a few hours. Most people recover from meningitis. However, permanent disabilities (such as brain damage, hearing loss, and learning disabilities) can result from the infection.
There are several types of bacteria that can cause meningitis. Leading causes in the United States include
- Streptococcus pneumoniae
- Group B Streptococcus
- Neisseria meningitidis
- Haemophilus influenzae
- Listeria monocytogenes
On average, bacterial meningitis caused about 4,100 cases and 500 deaths in the United States each year between 2003 and 2007.
These bacteria can also be associated with another serious illness, sepsis. Sepsis is the body’s overwhelming and life-threatening response to infection that can cause tissue damage, organ failure, and death.
Meningitis is an inflammation of the membranes (meninges) surrounding your brain and spinal cord.
The swelling from meningitis typically triggers symptoms such as headache, fever and a stiff neck.
Most cases of meningitis in the U.S. are caused by a viral infection, but bacterial and fungal infections are other causes. Some cases of meningitis improve without treatment in a few weeks. Others can be life-threatening and require emergent antibiotic treatment.
Seek immediate medical care if you suspect that someone has meningitis. Early treatment of bacterial meningitis can prevent serious complications.
Bacterial meningitis is the most serious type of meningitis. It can lead to death or permanent disability. It is a medical emergency.
Meningitis affects the meninges, the membranes that surround the brain and spinal cord and protect the central nervous system (CNS), together with the cerebrospinal fluid.
In 2006, the mortality rate for bacterial meningitis was 34 percent, and 50 percent of patients experienced long-term effects after recovery.
For this reason, treatment with antibiotics must start as soon as possible.
Several types of bacteria can cause bacterial meningitis, including Streptococcus pneumoniae (S. pneumoniae) and Group B Streptococcus.
Other types of meningitis include viral, parasitic, fungal, and non-infectious meningitis, but the bacterial type is the most severe.
Vaccines have dramatically reduced the incidence of bacterial meningitis.
Who gets bacterial meningitis?
Children between the ages of 1 month and 2 years are the most susceptible to bacterial meningitis.
Adults with certain risk factors are also susceptible. You are at higher risk if you abuse alcohol, have chronic nose and ear infections, sustain a head injury or get pneumococcal pneumonia.
You are also at higher risk if you have a weakened immune system, have had your spleen removed, are on corticosteroids because of kidney failure or have a sickle cell disease.
Additionally, if you have had brain or spinal surgery or have had a widespread blood infection you are also a higher risk for bacterial meningitis.
Outbreaks of bacterial meningitis also occur in living situations where you are in close contact with others, such as college dormitories or military barracks.
Bacterial meningitis can be caused by a range of bacteria, including:
- Haemophilus influenzae (H. influenzae)type B (Hib)
- Neisseria meningitides (N. meningitides)
- Streptococcus pneumoniae (S. pneumonia)
- Listeria monocytogenes (L. monocytogenes
- Group B Streptococcus
At different ages, people are more likely to be affected by different strains.
The bacteria that cause meningitis usually pass from one person to another, for example, through droplets in coughs and sneezes or through saliva or spit. Some types can spread through food.
Group B streptococcus can pass from mothers to newborns during delivery.
Some people are carriers. They have the bacteria, but they do not develop symptoms. Living in a house with either a carrier or someone who has meningitis increases the risk.
It is important to follow the recommended vaccination schedule to prevent meningitis. H. influenzais the main cause of bacterial meningitis in children under 5 in countries that do not offer the Hib vaccine.
The bacteria most often responsible for bacterial meningitis are common in the environment and can also be found in your nose and respiratory system without causing any harm.
Sometimes meningitis occurs for no known reason. Other times it occurs after a head injury or after you have had an infection and your immune system is weakened.
Common causes of bacterial meningitis vary by age group:
- Newborns:Group B Streptococcus, Streptococcus pneumoniae, Listeria monocytogenes, Escherichia coli
- Babies and children:Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus
- Teens and young adults:Neisseria meningitidis, Streptococcus pneumoniae
- Older adults:Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib), group B Streptococcus, Listeria monocytogenes.
- Group B Streptococcaland coli
Bacteria that enter the bloodstream and travel to the brain and spinal cord cause acute bacterial meningitis. But it can also occur when bacteria directly invade the meninges. This may be caused by an ear or sinus infection, a skull fracture, or, rarely, after some surgeries.
Several strains of bacteria can cause acute bacterial meningitis, most commonly:
- Streptococcus pneumoniae (pneumococcus). This bacterium is the most common cause of bacterial meningitis in infants, young children and adults in the United States. It more commonly causes pneumonia or ear or sinus infections. A vaccine can help prevent this infection.
- Neisseria meningitidis (meningococcus). This bacterium is another leading cause of bacterial meningitis. These bacteria commonly cause an upper respiratory infection but can cause meningococcal meningitis when they enter the bloodstream. This is a highly contagious infection that affects mainly teenagers and young adults. It may cause local epidemics in college dormitories, boarding schools and military bases. A vaccine can help prevent infection.
- Haemophilus influenzae (haemophilus). Haemophilus influenzae type b (Hib) bacterium was once the leading cause of bacterial meningitis in children. But new Hib vaccines have greatly reduced the number of cases of this type of meningitis.
- Listeria monocytogenes (listeria). These bacteria can be found in unpasteurized cheeses, hot dogs and luncheon meats. Pregnant women, newborns, older adults and people with weakened immune systems are most susceptible. Listeria can cross the placental barrier, and infections in late pregnancy may be fatal to the baby.
Viral meningitis is usually mild and often clears on its own. Most cases in the United States are caused by a group of viruses known as enteroviruses, which are most common in late summer and early fall. Viruses such as herpes simplex virus, HIV, mumps, West Nile virus and others also can cause viral meningitis.
Slow-growing organisms (such as fungi and Mycobacterium tuberculosis) that invade the membranes and fluid surrounding your brain cause chronic meningitis. Chronic meningitis develops over two weeks or more. The symptoms of chronic meningitis — headaches, fever, vomiting and mental cloudiness — are similar to those of acute meningitis.
Fungal meningitis is relatively uncommon and causes chronic meningitis. It may mimic acute bacterial meningitis. Fungal meningitis isn’t contagious from person to person. Cryptococcal meningitis is a common fungal form of the disease that affects people with immune deficiencies, such as AIDS. It’s life-threatening if not treated with an antifungal medication.
Other meningitis causes
Meningitis can also result from noninfectious causes, such as chemical reactions, drug allergies, some types of cancer and inflammatory diseases such as sarcoidosis.
Early meningitis symptoms may mimic the flu (influenza). Symptoms may develop over several hours or over a few days.
Possible signs and symptoms in anyone older than the age of 2 include:
- Sudden high fever
- Stiff neck
- Severe headache that seems different than normal
- Headache with nausea or vomiting
- Confusion or difficulty concentrating
- Sleepiness or difficulty waking
- Sensitivity to light
- No appetite or thirst
- Skin rash (sometimes, such as in meningococcal meningitis)
Risk factors for meningitis include:
- Skipping vaccinations.Risk rises for anyone who hasn’t completed the recommended childhood or adult vaccination schedule.
- Most cases of viral meningitis occur in children younger than age 5. Bacterial meningitis is common in those under age 20.
- Living in a community setting.College students living in dormitories, personnel on military bases, and children in boarding schools and child care facilities are at greater risk of meningococcal meningitis. This is probably because the bacterium is spread by the respiratory route, and spreads quickly through large groups.
- Pregnancy increases the risk of listeriosis — an infection caused by listeria bacteria, which also may cause meningitis. Listeriosis increases the risk of miscarriage, stillbirth and premature delivery.
- Compromised immune system.AIDS, alcoholism, diabetes, use of immunosuppressant drugs and other factors that affect your immune system also make you more susceptible to meningitis. Having your spleen removed also increases your risk, and patients without a spleen should get vaccinated to minimize that risk.
Meningitis complications can be severe. The longer you or your child has the disease without treatment, the greater the risk of seizures and permanent neurological damage, including:
- Hearing loss
- Memory difficulty
- Learning disabilities
- Brain damage
- Gait problems
- Kidney failure
Common bacteria or viruses that can cause meningitis can spread through coughing, sneezing, kissing, or sharing eating utensils, a toothbrush or a cigarette.
These steps can help prevent meningitis:
- Wash your hands.Careful hand-washing helps prevent germs. Teach children to wash their hands often, especially before eating and after using the toilet, spending time in a crowded public place or petting animals. Show them how to vigorously and thoroughly wash and rinse their hands.
- Practice good hygiene.Don’t share drinks, foods, straws, eating utensils, lip balms or toothbrushes with anyone else. Teach children and teens to avoid sharing these items too.
- Stay healthy.Maintain your immune system by getting enough rest, exercising regularly, and eating a healthy diet with plenty of fresh fruits, vegetables and whole grains.
- Cover your mouth.When you need to cough or sneeze, be sure to cover your mouth and nose.
- If you’re pregnant, take care with food.Reduce your risk of listeriosis by cooking meat, including hot dogs and deli meat, to 165 F (74 C). Avoid cheeses made from unpasteurized milk. Choose cheeses that are clearly labeled as being made with pasteurized milk.
As several types of bacteria can cause bacterial meningitis, so a range of vaccines is necessary to prevent infection.
The first vaccine was created in 1981 to protect against 4 of the 13 subtypes of N. meningitides.
A survey of 17 million people in the U.S. found that the incidence of all types of meningitis fell by 31 percent from 1998 to 2007, after the introduction of routine vaccinations against meningitis-causing bacteria.
The meningococcal vaccine is the primary vaccine in the U.S. All children should have this at the age of 11 to 12 years and again at 16 years, when the risk of infection is higher.
The Hib vaccine protects children against H. Influenzae. Before its introduction in the U.S. in 1985, H. Influenzae infected over 20,000 children under 5 years annually, with a 3 to 6 percent mortality rate. Widespread vaccination has reduced the incidence of bacterial meningitis by over 99 percent.
The Hib vaccine is given in four doses at the ages of 2, 4, 6, and 12 to 15 months.
Side effects of the vaccines may include redness and soreness at the site of the injection and a fever. Always check with a doctor to ensure that no allergies to any part of the vaccinations are present.
To prevent the spread of bacterial meningitis and other diseases, it is important to practice good hygiene, such as frequent handwashing.
Being aware of the signs and symptoms of bacterial meningitis will make it easier to take immediate action can be taken if necessary.
Your family doctor or pediatrician can diagnose meningitis based on a medical history, a physical exam and certain diagnostic tests. During the exam, your doctor may check for signs of infection around the head, ears, throat and the skin along the spine.
You or your child may undergo the following diagnostic tests:
- Blood cultures. Blood samples are placed in a special dish to see if it grows microorganisms, particularly bacteria. A sample may also be placed on a slide and stained (Gram’s stain), then studied under a microscope for bacteria.
- Imaging. Computerized tomography (CT) or magnetic resonance (MR) scans of the head may show swelling or inflammation. X-rays or CT scans of the chest or sinuses may also show infection in other areas that may be associated with meningitis.
- Spinal tap (lumbar puncture). For a definitive diagnosis of meningitis, you’ll need a spinal tap to collect cerebrospinal fluid (CSF). In people with meningitis, the CSF often shows a low sugar (glucose) level along with an increased white blood cell count and increased protein.
CSF analysis may also help your doctor identify which bacterium caused the meningitis. If your doctor suspects viral meningitis, he or she may order a DNA-based test known as a polymerase chain reaction (PCR) amplification or a test to check for antibodies against certain viruses to determine the specific cause and determine proper treatment.
Some forms of bacterial meningitis are preventable with the following vaccinations:
- Haemophilus influenzae type b (Hib) vaccine.Children in the United States routinely receive this vaccine as part of the recommended schedule of vaccines, starting at about 2 months of age. The vaccine is also recommended for some adults, including those who have sickle cell disease or AIDS and those who don’t have a spleen.
- Pneumococcal conjugate vaccine (PCV13).This vaccine also is part of the regular immunization schedule for children younger than 2 years in the United States. Additional doses are recommended for children between the ages of 2 and 5 who are at high risk of pneumococcal disease, including children who have chronic heart or lung disease or cancer.
- Pneumococcal polysaccharide vaccine (PPSV23).Older children and adults who need protection from pneumococcal bacteria may receive this vaccine. The Centers for Disease Control and Prevention recommends the PPSV vaccine for all adults older than 65, for younger adults and children age 2 and up who have weak immune systems or chronic illnesses such as heart disease, diabetes or sickle cell anemia, and for those who don’t have a spleen.
- Meningococcal conjugate vaccine.The Centers for Disease Control and Prevention recommends that a single dose be given to children ages 11 to 12, with a booster shot given at age 16. If the vaccine is first given between ages 13 and 15, the booster shot is recommended between ages 16 and 18. If the first shot is given at age 16 or older, no booster is necessary.
This vaccine can also be given to younger children who are at high risk of bacterial meningitis or who have been exposed to someone with the disease. It’s approved for use in children as young as 9 months old. It’s also used to vaccinate healthy but previously unvaccinated people who have been exposed in outbreaks.
The incidence of meningitis in the U.S. has dropped considerably since its vaccine was introduction.
Treatment for bacterial meningitis normally involves admission to the hospital, and possibly an intensive care unit.
Antibiotics are essential, and these may be started before the results of tests come back, possibly before arrival at the hospital.
- Antibiotics: These are usually given intravenously.
- Corticosteroids: These may be given if inflammationis causing pressure in the brain, but studies show conflicting results.
- Acetaminophen, or paracetamol:Together with cool sponge baths, cooling pads, fluids, and room ventilation, these reduce fever.
- Anticonvulsants:If the patient has seizures, an anticonvulsant, such as phenobarbital or Dilantin, may be used.
- Oxygen therapy: Oxygen will be administered to assist with breathing.
- Fluids: Intravenous fluids can prevent dehydration, especially if the patient is vomiting or cannot drink.
- Sedatives:These will calm the patient if they are irritable or restless.
Blood tests may be used to monitor the patient’s levels of blood sugar, sodium, and other vital chemicals.
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