Meningitis is primarily caused by infections, specifically from bacteria, viruses, parasites, and fungi.
These infectious agents can spread to the meninges (the protective membranes covering the brain and spinal cord) through various ways:
- Bacterial Meningitis: Often arises from bacteria that colonize the nose and throat and then spread to the brain via the bloodstream. Some common bacterial culprits include:
- Streptococcus pneumoniae
- Neisseria meningitidis
- Haemophilus influenzae type b (Hib)
- Listeria monocytogenes
- Group B Streptococcus (especially in newborns).
- Viral Meningitis: Typically less severe than bacterial meningitis, it's often caused by viruses that also cause other illnesses, such as:
- Enteroviruses (most common cause)
- Herpesviruses
- Mumps virus
- West Nile virus.
- Fungal Meningitis: Less common, it's often seen in individuals with weakened immune systems. Examples include:
- Cryptococcus
- Histoplasma
- Coccidioides
- Parasitic Meningitis: This is a rare form of meningitis, contracted from parasites found in contaminated food, water, or soil.
In addition to infections, in rarer cases, meningitis can result from:
- Non-infectious causes: such as certain medications, autoimmune diseases, and cancer. These are much less common than infectious causes.
Therefore, while the immediate cause of meningitis is inflammation of the meninges, the underlying origin typically traces back to an infectious agent such as bacteria, viruses, fungi, or parasites gaining access to the central nervous system.
