What are the Causes of Meningitis?

Meningitis is usually caused by bacteria or viral infections.

Viruses that can cause meningitis include:

Enteroviruses (most common cause of viral infections)
Herpes simplex virus type 2
Varicella zoster virus
Mumps virus
HIV

Bacterial infections commonly include infection by:

Neisseria meningitidis
Haemophilus influenza B
Streptococcus pneumoniae

Other less common causes of meningitis include infections by fungi, amoeba and protozoa.

Non-infectious causes of meningitis include systemic diseases like SLE, sarcoidosis, polyarteritis nodosa, rheumatoid arthritis, toxins, certain medications and malignancies. Meningitis caused by non-infectious agents is called sterile meningitis because no microorganism is isolated from the spinal fluid.