Meningitis is usually caused by a viral or bacterial infection.
Viral meningitis is the most common and least serious type. Bacterial meningitis is rare, but can be very serious if not treated.
Several different viruses and bacteria can cause meningitis, including:
- meningococcal bacteria – there are several different types, called A, B, C, W, X, Y and Z
- pneumococcal bacteria
- Haemophilus influenzae type b (Hib) bacteria
- enteroviruses – viruses that usually only cause a mild stomach infection
- the mumps virus
- the herpes simplex virus – a virus that usually causes cold sores or genital herpes
A number of meningitis vaccinations provide protection against many of the infections that can cause meningitis.
The viruses and bacteria that cause meningitis can be spread through:
The infection is usually spread by people who carry these viruses or bacteria in their nose or throat, but are not ill themselves.
The infection can also be spread by someone with meningitis, although this is less common.
It's possible to get meningitis more than once.
Anyone can potentially get meningitis, but it's more common in:
- babies and young children
- teenagers and young adults
- elderly people
- people with a weak immune system – for example, those with HIV and those having chemotherapy
You can reduce the risk of getting meningitis by ensuring all your vaccinations are up-to-date.