Meningitis is mainly bacterial or viral. The classic triad of fever, neck stiffness, and altered mental status is present in only 44% of cases. Diagnosis is by cerebrospinal fluid analysis.

72,500 (US); 1,650,000 (Global)
Meningitis, bacterial, acute; Meningitis, nonbacterial; Meningitis, aseptic; Meningitis, viral;
Estimated: 1 day to several weeks;
Fever, headache, meningismus, and altered mental status;
Droplet until 24 hours after beginning effective therapy for Haemophilus influenzae, type b and Neisseria meningitidis; Standard for other types; [CDC 2007 Guideline for Isolation Precautions]
Streptococcus pneumoniae (about 50% of cases) and Neisseria meningitidis (about 25% of cases) are the most common causes of bacterial meningitis in immunocompetent adults. The cause of viral meningitis can be identified in about 75-90% of cases with the most common being enterovirus, HSV type 2, HIV, VZV, and arboviruses. [Harrisons, p. 1053, 1057] "The nonspecific term aseptic meningitis describes an inflammatory process involving the meninges, usually accompanied by a mononuclear pleocytosis, without evidence of pyogenic bacterial infection on Gram stain or culture." Aseptic meningitis includes viral meningitis (most cases) as well as nonpyogenic bacterial and fungal meningitis. Enteroviruses cause more than 60% of viral meningitis. Findings associated with enterovirus meningitis are a biphasic course, sore throat, diarrhea, vomiting, myalgia, pleurodynia, pericarditis, rash, hand-foot-and-mouth disease, and petechial rash. [Cecil, p. 2452-4]

Classic triad of fever, neck stiffness, and altered mental status is present in only 44% of cases. [ABX Guide] Opisthotonus is a possible symptom of infants with meningitis. [Cohen, p.180] Following viral meningitis, some patients may have residual weakness lasting a year or more. [CCDM, 401-2] Viral meningitis may be accompanied by skin manifestations of viral infections, e.g., vesicles and herpangina (enteroviral infections) and maculopapular rash (other viral infections), [5MCC-2020] Neck stiffness: patients resist flexion but not gentle side-to-side rotation. If coma ensues, neck stiffness disappears. [Cecil, p. 2445] Seizures occur in 20-40% of patients with bacterial meningitis, but they are not typical of viral meningitis. [Harrison ID, p. 337, 342] Chronic meningitis develops over weeks or months and is most commonly idiopathic. Other causes are Mycobacterium tuberculosis, Candida, Aspergillus, Cryptococcus neoformans, Histoplasma spp., and Coccidioides spp. [PPID, p. 1176]

CT or MRI is indicated prior to lumbar puncture (LP) if recent head trauma, immunocompromised, known malignancy, focal neurological findings; papilledema, or stupor/coma. When any of these conditions exist, antimicrobial therapy should not be delayed; it should be administered after obtaining blood cultures and prior to neuroimaging and LP. When bacterial meningitis is suspected, antibiotics should be started without delay. [Harrisons, p. 1052-3] In most cases, do LP promptly and then start antibiotics. If papilledema, focal neurological findings, or severe CNS depression, start antibiotics, then CT, then LP if CT negative. [ABX Guide] "Immunocompetent patients with a normal level of consciousness, no prior antimicrobial treatment, and a cerebrospinal fluid (CSF) profile consistent with viral meningitis (lymphocytic pleocytosis and a normal glucose concentration) can often be treated as outpatients if appropriate contact and monitoring can be ensured." [Harrison ID, p. 334]

In classic bacterial meningitis: White blood cells are 10-10,000/uL with neutrophils predominating; Protein is >45 mg/dl; Glucose is <40 mg/dL; Opening pressure is >180 mmH2O; Bacterial cultures are positive in >80%; Gram stain is positive in >60%. Latex agglutination tests (being replaced by PCR tests of CSF) are especially useful in patients pretreated with antibiotics and are available for S. pneumoniae, N. meningitidis, N. influenzae type b, Group B streptococcus, and E. coli. [Harrisons, p. 1054]
"Consider CT first if focal neurological findings, papilledema, new seizures, immunocompromised state or severely depressed sensorium (GCS < 10) or defer if bleeding risks are high (coagulopathy, thrombocytopenia) . . ." [ABX Guide]
  • >arthralgia
  • >fatigue, weakness
  • >fever
  • >fever, biphasic or relapsing
  • >myalgia
  • E pharyngitis
  • E stomatitis
  • G abdominal pain
  • G constipation
  • G diarrhea
  • G nausea, vomiting
  • H leukocytosis
  • H leukopenia
  • H thrombocytopenia
  • N confusion, delirium
  • N headache
  • N lethargy
  • N muscle weakness
  • N opisthotonus
  • N paresthesia
  • N seizure
  • N stiff neck
  • O conjunctivitis, acute
  • R chest pain
  • R cough
  • S papules or plaques
  • S petechiae and ecchymoses
  • S rash (exanthem)
  • S rash on palms
  • S skin blister or vesicles
  • *arthritis
  • *bleeding tendency
  • *blindness
  • *cranial neuropathy
  • *endocarditis
  • *meningitis
  • *myelitis
  • *paralysis
  • *pericarditis
  • *sepsis
  • *shock
  • *stupor, coma
  • *weight loss




Inhalation, Ingestion, Needle (Includes Drug Abuse), Scalpel or Transfusion, Skin or Mucous Membranes (Includes Conjunctiva), Animal Bite, Swimming, Sexual Contact
Fleas, Biting Flies, Lice, Mites, Mosquitoes, Ticks
Person-to-Person, Human Fecal-Oral, Fecally Contaminated Soil, Animal Excreta, Animal Tissue, Soil or Dust (Ingesting or Inhaling), Eating Contaminated Food, Eating Contaminated or Infected Meat, Eating Infected or Toxin-Containing Fish, Eating Contaminated Mollusks or Crustacean, Eating Unpasteurized Milk or Cheese, Eating Contaminated Produce, Waterborne (Ingesting, Inhaling, or Swimming)
Birds and Poultry, Cattle, Goats and Sheep, Cats, Deer, Elk and Antelope, Dogs, Fish and Shellfish, Horses, Monkeys, Rabbits, Rodents, Swine, Human, Wild Animals
  • AIDS patients
  • Cancer patients
  • Injection drug users
1. (US) Bacterial meningitis: >2.5 cases/100,000; Viral meningitis: about 67,500 cases/year; [Harrison ID, p. 334, 342] Calculate: 67,500 + (2.5 x 3000) = 72,500;
2. (Global) 20 X US cases/yr;