From the Guidelines
Meningitis is primarily caused by bacterial, viral, fungal, and parasitic infections, with the most severe form being bacterial meningitis, commonly caused by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b, as stated in the 2016 UK joint specialist societies guideline on the diagnosis and management of acute meningitis and meningococcal sepsis in immunocompetent adults 1. The causes of meningitis can be broken down into several categories, including:
- Bacterial meningitis, which is the most severe form and can be life-threatening if left untreated
- Viral meningitis, which is more common but typically less severe
- Fungal meningitis, which results from fungi like Cryptococcus and Candida
- Parasitic meningitis, which can be caused by organisms such as Angiostrongylus cantonensis Non-infectious causes of meningitis include certain medications, cancers, autoimmune disorders, and head injuries. The likelihood of any specific aetiology depends on a range of factors, including age, immune status, and community settings, as outlined in Table 2 of the 2016 guideline 1. Some key considerations for specific demographic groups include:
- Young adults: viral meningitis is more common than bacterial, especially in women in their 20s-40s
- Older adults: pneumococcal disease is more common in over 50s, and Listeria is more common in over 60s
- Immunocompromised individuals: Cryptococcal meningitis is commonest in those with a CD4 count <100, and TB meningitis is an important consideration at all CD4 counts The treatment approach for meningitis depends on the causative agent, with bacterial meningitis requiring immediate antibiotic therapy, often with ceftriaxone 2g IV every 12 hours for 7-14 days, while viral cases typically resolve with supportive care, as stated in the 2016 guideline 1. Prompt identification of the cause is crucial, as bacterial meningitis can be life-threatening within hours if left untreated, and the mortality rate of community-acquired bacterial meningitis is high, approximately 20% for all causes and up to 30% in pneumococcal meningitis, increasing with age 1.
From the Research
Causes of Meningitis
The causes of meningitis can be categorized into several types, including:
- Bacterial meningitis: caused by bacteria such as Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae 2, 3, 4, 5
- Viral meningitis: caused by viruses such as enteroviruses, herpesviruses, and influenza viruses 6
- Fungal infections: although less common, fungal infections can also cause meningitis 6
Bacterial Meningitis Causes
Bacterial meningitis is caused by several types of bacteria, including:
- Streptococcus pneumoniae 2, 3, 4, 5
- Neisseria meningitidis 2, 3, 4, 5
- Haemophilus influenzae 2, 3, 4, 5
- Streptococcus agalactiae (group B Streptococcus) 3
Viral Meningitis Causes
Viral meningitis is caused by several types of viruses, including: