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Meningitis is an inflammation of the coverings of the brain (the meninges),
which can be caused by viruses, bacteria or fungi.

1. VIRAL MENINGITIS
Viral meningitis is the most common form of meningitis in the UK and is linked to a large number of viruses. Anyone can get viral meningitis, but it is most common in young children. The viruses that most commonly cause meningitis are:

• Enteroviruses (coxsackie, echovirus, and the polio virus)
• Mumps (the mumps virus)
• Glandular fever (the Epstein-Barr virus)
• Herpes simplex, Human Immunodeficiency Virus (HIV) and Cytomegalovirus (CMV).

Enteroviruses

Enteroviruses are the most common cause of meningitis in children in the UK. These viruses enter through the mouth, multiply in the body and are excreted in the faeces. The infection usually produces mild or moderate symptoms, is not life-threatening and lasts only a short time.

Mumps

Meningitis in mumps may occur before, or follow the swelling of the glands at the angle of the jaw, which are called the parotid glands. Symptoms are usually mild and most people make a full recovery after one to seven days, although some may get a severe form which generally occurs after the glands swell.

Glandular fever

Meningitis is rare and occurs in less than half of one per cent of cases of glandular fever. It usually starts about one week into the illness and serious complications affecting the nervous system are rare.

Herpes simplex, HIV or CMV meningitis

People who have weakened immune systems, injecting drug users and people who practice unsafe sex may be at increased risk from this type of meningitis.

2. BACTERIAL MENINGITIS

Bacterial meningitis is potentially life-threatening, but fortunately rare. The bacteria that cause the infection can be of any type, but the three bacteria that most commonly cause acute meningitis spread from the upper respiratory tract (the nose, throat, sinuses and lungs). They are:

• Neisseria meningitidis (in meningococcal meningitis)
• Streptococcus pneumoniae (in pneumococcal meningitis)
• Haemophilus influenzae (in haemophilus meningitis)

Other forms of bacterial meningitis include E. coli meningitis (Escherichia coli), which can occur in newborn babies after infection from the mother’s birth canal. Elderly people, those with weakened immune systems, heavy alcohol users, or those who have had contact with people who have tuberculosis may be more at risk of TB meningitis (Mycobacterium tuberculosis).

Meningococcal meningitis

This is caused by infection with a bacteria called Neisseria meningitidis. This bacteria can also cause blood poisoning (septicaemia) if it invades the bloodstream. Meningitis and septicaemia are often found together. About two to three in every hundred thousand people each year get a meningococcal illness.

The infection is mainly transmitted from person to person by coughing or in the saliva of those who carry the bacteria in the throat and nose in a harmless state. Ten to 20 per cent of the general population are carriers. During epidemics as many as 95 per cent of healthy people may carry the bacteria, but less than one per cent ever get meningitis.

Infections can be isolated, but can also occur in outbreaks in crowded places, such as army barracks or colleges. Meningococcal meningitis can affect people of any age, but is most common below the age of 15 years, and most cases have been seen in five-year-olds. Recently in the UK there has been a noticeable increase in the numbers of 15- to 24-year-olds affected. This may suggest an increased likelihood of outbreaks of meningococcal infection in institutions, e.g. schools, colleges and universities.

Meningococcal meningitis is a severe, life-threatening infection. There are three common strains of meningococcus called group A, group B and group C. Group B strains are the most common, but group C strains are becoming more frequent and account for a third of cases.

If Neisseria meningitidis produces septicaemia, other organs in the body can become infected, e.g. the eyes, heart, lungs and brain. Septicaemia is a common cause of death, and the proportion of people who die from this infection is more than three times greater than the proportion who die from meningococcal meningitis.

The death rate for meningococcal meningitis is four times higher in teenagers than in children under five years old. The overall mortality rate is between six and 10 per cent.

Pneumococcal meningitis

This is caused by a bacteria called Streptococcus pneumoniae, which is a major cause of ear infections, pneumonia, and septicaemia. Meningitis often follows pneumonia or a sinus infection and commonly occurs with septicaemia. There are one or two new cases of pneumococcal meningitis per hundred thousand people each year and it usually occurs in isolated cases rather than in outbreaks.

The infection is most common in those under two and over 60 years of age. People who have had their spleen removed (splenectomy) are at increased risk of developing this form of meningitis.

Vaccination against the most common strains of pneumococcus has been available for some time and is recommended for anyone who has had a splenectomy. However, there are many different strains of the Streptococcus bacteria, and because of the large number of strains and the relatively poor response to vaccines, vaccination may not prevent infection. Treatment with penicillin is generally effective, but there are now strains which have developed resistance to this antibiotic.

Pneumococcal meningitis is the most serious form of acute meningitis and has a mortality rate of 20 per cent. More than one third of survivors will be left with neurological problems e.g. deafness, fits or weakness. The mortality rate is higher in adults than in children and increases in those who go into a coma or have pneumonia as well.

Haemophilus meningitis

This is caused by a bacteria called Haemophilus influenzae. Haemophilus influenzae meningitis used to be the most common cause of bacterial meningitis in children under five years old, with an overall rate of about 16 new cases per million of the population each year. Since the introduction of Haemophilus influenzae type b immunisation in 1992, the frequency of haemophilus meningitis has fallen by 87 per cent and there are now probably less than three new cases per million of the population each year.

E. coli meningitis

E. coli meningitis is the most common form of meningitis occurring in the first month of life. The infection is more common in babies where there have been complications during the birth and where the mother has an E. coli infection of the urinary tract or uterus. In more than 50 per cent of cases of E. coli meningitis, the baby also has septicaemia.

There may be few signs of meningitis in infants, especially in those that are born pre-term. If any infant is unusually drowsy, irritable and feverish, E. coli meningitis may be a possible cause, particularly if no other source of infection can be identified. The mortality rate can be as high as 50 per cent and is particularly high in pre-term infants.

TB meningitis

TB meningitis is caused by an infection by Mycobacterium tuberculosis. It is relatively uncommon in the UK, but may be on the increase, especially in people whose immune systems have become weakened e.g. people with AIDS,heavy alcohol users and people who have travelled from areas where the infection is common in the population.

TB meningitis most commonly affects very young and very old people who are exposed to the bacteria without being adequately immunised by the BCG vaccination.

3. FUNGAL MENINGITIS

Fungal meningitis is rare and usually only occurs in people whose immune systems have become weakened e.g. in those with diabetes or HIV/AIDS, or very elderly people. The organisms commonly causing fungal meningitis are Cryptococcus neoformans (in cryptococcal meningitis) and Candida albicans (in candidal meningitis). The signs of meningitis may be less obvious thanbacterial meningitis and may appear more gradually. The death rate is high.

Bacterial and fungal meningitis can sometimes also be connected with a brain abscess. An abscess is a collection of inflamed or infected tissue (pus) that forms a cavity in the brain. The spread of the infection to the brain is usually via the blood (septicaemia) or occasionally from infection close to the brain (e.g. ear and sinus infections).

Is there anything that could make someone more likely to catch meningitis?

Bacterial meningitis is more common if there has been:

• a fractured skull
• spina bifida
• a previous operation on the brain (e.g. shunt insertion)
• previous ear, sinus or chest infection
• a recent trip abroad
• mosquito bites
• contact with someone who may have had meningitis or TB
• contact with sewers during work
• drinking from mountain streams.