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
• Seizures
• Sleepiness or difficulty waking
• Sensitivity to light
• No appetite or thirst
• Skin rash (sometimes, such as in meningococcal meningitis)

Signs in newborns

Newborns and infants may show these signs:

• High fever
• Constant crying
• Excessive sleepiness or irritability
• Inactivity or sluggishness
• Poor feeding
• A bulge in the soft spot on top of a baby's head (fontanel)
• Stiffness in a baby's body and neck

Infants with meningitis may be difficult to comfort, and may even cry harder when held.

Viral infections are the most common cause of meningitis, followed by bacterial infections and, rarely, fungal infections. Because bacterial infections can be life-threatening, identifying the cause is essential.

Bacterial meningitis

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 lunchmeats. 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

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.

Chronic 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 signs and symptoms of chronic meningitis — headaches, fever, vomiting and mental cloudiness — are similar to those of acute meningitis.

Fungal 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.

Risk factors for meningitis include:

• Skipping vaccinations. Risk rises for anyone who hasn't completed the recommended childhood or adult vaccination schedule.
• Age. 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. Pregnancy increases the risk of listeriosis — an infection caused by listeria bacteria, which may also 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 anyone 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
• Seizures
• Kidney failure
• Shock
• Death