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What is meningitis?
Meningitis is an inflammation of the meninges, the protective layers surrounding the brain and spinal cord. The most common cause is a viral infection; however, the most serious cause is a bacterial infection (bacterial meningitis).
There are an estimated 1.2 million cases of bacterial meningitis in the world every year and about 180,000 deaths.  Bacterial meningitis is estimated to cause 2% of all child deaths in the world. 
There are several possible causes of meningitis. The inflammation can be the result of infection with bacteria, viruses or fungi. It can also result from non-infectious causes such as inflammatory diseases.
Bacterial meningitis can be extremely serious and is treated as a medical emergency as it can be fatal, if not appropriately treated. Bacterial meningitis can be spread through contact with saliva and nasal droplets. It can be caught through close contact, such as sharing a room or household with an infected person.
Some of the most common bacterial species that cause meningitis include:
- Streptococcus pneumoniae;
- Neisseria meningitidis (also known as Meningococcus), and;
- Streptococcus agalactiae / group B streptococcus.
Other bacterial species known to cause meningitis are
- Haemophilus influenza type B;
- Listeria monocytogenes, and;
- Escherichia coli (E. coli).
Viral meningitis is more common and normally milder than bacterial meningitis, though it can be highly contagious. Most people recover from viral meningitis without any permanent damage. It is common in children and young adults.
Viruses that can cause meningitis include:
Viruses that cause diseases such as measles, mumps and the flu can also result in meningitis, as a complication of these diseases. However, infection with these viruses can be preventable by vaccination.
Fungal meningitis is rare and not contagious. It can develop when a fungus gets into your bloodstream or central nervous system. Fungal meningitis can develop very slowly and generally occurs in people with a weak immune system.
Infection is often a result of inhalation of the fungal spores. These spores are normally found in the soil or in animal droppings, but are sprayed into the air when dust or droppings are disturbed, such as by being kicked or stepped on.
Rarely, meningitis is caused by infection with single-celled parasites, such as amoebas. This typically occurs when a person swims in water where the parasites are found and the contaminated water enters the nose. This rare condition is dangerous and often fatal.
Inflammation of the meninges can also occur without any infection. Some causes of non-infectious meningitis include:
Weak immune system
Factors that can affect the immune system include:
- Age (young children and elderly people);
- Disease (for example, HIV/AIDS), and;
- Medical procedures, such as chemotherapy or organ transplant.
People in an environment where meningitis infections are more likely to occur include:
- Young adults forced to sleep in crowded conditions, such as university dorms or army barracks, and;
- People living in, or travelling to, the 'meningitis belt', a region of sub-Saharan Africa where bacterial meningitis is common. Once every 8-12 years, the region experiences widespread outbreaks that may cause tens of thousands of deaths.
Signs and symptoms
The signs and symptoms of meningitis can closely resemble those of the flu. They can appear quickly, sometimes hours after infection, or over a few days. It is not possible for a person to diagnose themselves or family members with meningitis. It is therefore very important to seek professional medical help if you suspect meningitis.
Symptoms in adults
The 'classic' symptoms of meningitis in adults include:
- Severe headache;
- Stiff neck, and;
- Altered mental state - confusion or trouble concentrating, unintelligible speech.
At least two of these symptoms appear in nearly all people with bacterial meningitis. Additional symptoms of meningitis may include:
- Head and neck arching backwards;
- Joint pain, muscle pain;
- Vomiting, nausea;
- Sleepiness or difficulty waking up;
- Skin rash - reddish-purple spots the size of pinpricks, or larger dark purple bruise-like spots;
- Sensitivity to light;
- Rapid breathing, and;
- Lack of appetite.
Symptoms in infants
In infants, the symptoms of meningitis might appear slightly different. They include:
- High fever;
- Irritability, constant crying, moaning or grunting;
- Lack of appetite, no interest in feeding;
- Vomiting, nausea;
- Stiffness in the body and neck, and;
- A swelling in the soft spot on top of the baby's head (fontanelle).
Methods for diagnosis
Meningitis can be difficult to diagnose in the early stages, because the symptoms can be similar to the flu. If your doctor suspects that you have meningitis, they may perform one or more of the following tests:
- Physical examination to check for signs of infection;
- Lumbar puncture (spinal tap), to take a sample of fluid from around your spinal cord;
- Blood sample to check for infection, and;
- Computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan of your head to check for other causes of symptoms. This may be performed in some people before the lumbar puncture to exclude conditions that may make lumbar puncture dangerous. In most cases of suspected or likely meningitis, the lumbar puncture is performed first and is the most important test.
Types of treatment
The type of treatment depends on the cause of the meningitis.
Bacterial meningitis is promptly treated in a hospital with high doses of antibiotics, given intravenously.
Non-bacterial meningitis treatment
Treatment of non-bacterial meningitis is usually managing the symptoms, providing plenty of fluids and making sure that the inflammation does not cause pressure on the brain. Meanwhile, the person's immune system takes care of the infecting virus.
In some cases of viral meningitis where the immune system is weak, specific antiviral therapy may be recommended.
Fungal meningitis is normally treated with antifungal medication, such as amphotericin B or fluconazole. Parasitic meningitis is treated with antiparasitic medications.
Bacterial meningitis is still a dangerous condition today, and can lead to serious complications and death. Untreated bacterial meningitis is usually fatal. Even with treatment, there is still a real chance of death or serious disability.
After-effects of the infection are also more pronounced in bacterial meningitis than in other kinds.
Viral meningitis is usually less severe and will normally clear up on its own in 2-4 weeks, but complications can still occur.
Meningitis complications result from the damage that the inflammation causes to various areas of the brain. Complications can include:
- Hearing loss;
- Memory impairment;
- Learning disabilities (temporary or permanent);
- Coordination and balance problems;
- Epilepsy or seizures;
- Cerebral palsy;
- Speech problems;
- Vision loss;
- Kidney failure;
- Paralysis, and;
Some people recovering from meningitis may suffer from after-effects of the inflammation. These problems can linger for some time after the episode has passed, but usually get better eventually. They can include:
- Hearing difficulties;
- Ringing in the ears (tinnitus);
- Recurring headaches;
- Vision problems, and;
- Impaired thinking and learning.
Bacterial meningitis can lead to contamination of the bloodstream with the infecting bacteria (septicaemia or bacteraemia), a dangerous complication of meningitis. Blood infections can lead to arthritis, gangrene, kidney failure, septic shock and death.
There is no guarantee against meningitis; complete prevention is not yet available. You can lower the risk of bacterial meningitis by avoiding close contact (sharing a room, household, dormitory, kissing or sharing food and cutlery) with an infected person.
Close contacts (family, household members) of people that have been diagnosed with bacterial meningitis may receive antibiotic treatment to prevent infection and development of disease.
Vaccines are available against the most dangerous types of bacteria that cause bacterial meningitis, as well as against some of the viruses that cause meningitis. The vaccines do not cover all possible infectious causes of meningitis. In many countries, these vaccines are offered as part of the regular childhood vaccination schedule. Vaccination is also often recommended for:
- Unvaccinated older children about to enter secondary school;
- Young adults who are expected to enter situations where they will be sleeping in crowded conditions, such as university dorms or army barracks, and;
- People living in or travelling to at-risk areas.