Causes of Meningitis
There are various causes of meningitis depending on the type of meningitis.
1. Bacterial meningitis
This type of meningitis is caused by bacteria like Streptococcus pneumoniae, Group B Streptococcus, Neisseria meningitides, Haemophilus influenzae, Listeria monocytogenes, and Escherichia coli. Mycobacterium tuberculosis, which generally causes tuberculosis or TB, is a less common cause of bacterial meningitis (called TB meningitis).
Bacteria can enter a person’s meninges in various ways as follows:
The spread of bacterial meningitis generally depends on the type of bacteria that causes it. Bacterial meningitis can spread from person to person and also via certain foods such as unpasteurized dairy or deli meats. A person can be a carrier for bacterial meningitis and pass it on to others without getting sick themselves.
Bacterial meningitis is a serious condition and requires medical attention right away. It can be life threatening or cause permanent disabilities, such as brain damage, hearing loss, and learning disabilities, in case the treatment is delayed.
2. Viral meningitis
Meningitis caused by a virus is called viral meningitis and it is the most common type. Non-polio enteroviruses are the most common cause of viral meningitis however, other viruses that cause this disease are mumps virus, herpes viruses (Epstein-barr virus, herpes simplex viruses, cytomegalovirus, and varicella-zoster virus), measles virus, influenza virus, arboviruses (west nile virus and zika virus), and lymphocytic choriomeningitis virus.
Most people get better on their own without treatment however infants and people with a weakened immune system are more likely to get a severe form of illness.
3. Fungal meningitis
It spreads from fungal infections at any other part of the body that goes and infects the brain and spinal cord. Some causes of fungal meningitis are Cryptococcus, Histoplasma, Blastomyces, Coccidioides, Candida, and Mucormycosis. It is most likely to affect immunocompromised individuals such as HIV patients, cancer patients or transplant recipients.
4. Parasitic meningitis
Various parasites can affect the brain or nervous system in many ways and cause meningitis. Overall, parasitic meningitis is much less common than viral and bacterial meningitis. Some parasites can cause a rare form of meningitis called eosinophilic meningitis, eosinophilic meningoencephalitis, or EM.
The three main parasites that can cause EM are Angiostrongylus cantonensis (neurologic angiostrongyliasis), Baylisascaris procyonis (baylisascariasis and neural larva migrans), and Gnathostoma spinigerum (neurognathostomiasis).
5. Amebic meningitis
Primary amebic meningoencephalitis (PAM) is caused by Naegleria fowleri and is a rare brain infection that is usually fatal. Naegleria fowleri is a free-living ameba (a single-celled living organism that is too small to be seen without a microscope).
Naegleria fowleri is found in soil and warm freshwater around the world. It grows best at higher temperatures up to 115°F (46°C) and can survive for short periods at higher temperatures.
6. Non-infectious meningitis
This type of meningitis is not caused due to pathogens that spread between people but due to reasons other than infections like cancers, systemic lupus erythematosus (lupus), certain medications, head injury, and brain surgery.