Meningitis most commonly starts when a viral or, less often, bacterial infection elsewhere in the body spreads to the brain and spinal cord. Rarely, it can be caused by other infections, medications, or illnesses like cancer.
Here's a more detailed breakdown:
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Viral Meningitis: This is the most common type. Viruses, often those that cause common illnesses like the flu or herpes, can sometimes spread to the meninges (the membranes surrounding the brain and spinal cord).
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Bacterial Meningitis: This is more serious than viral meningitis and can be life-threatening. Bacteria, such as Streptococcus pneumoniae or Neisseria meningitidis, can enter the bloodstream and then cross the blood-brain barrier to infect the meninges. Often, the bacteria originate from infections in the upper respiratory tract, such as a sinus infection or ear infection.
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Other Causes (Less Common): In rare cases, meningitis can be caused by:
- Fungal Infections: These are more likely in people with weakened immune systems.
- Parasitic Infections: Certain parasites can infect the brain and meninges.
- Non-Infectious Causes: These include allergic reactions to certain medications, autoimmune disorders (like lupus), and cancer.
In summary, meningitis typically starts as an infection in another part of the body that then spreads to the membranes surrounding the brain and spinal cord. The specific cause determines the severity and treatment of the disease.
