Infectious causes of dementia

Bacterial
- Syphilis, usually as general paralysis with emotional incontinence, irritability, grandiosity, euphoria, poor insight, apathy, delusions, and cognitive impairment
- Lyme meningoencephalomyelitis, with impaired executive function and reduced attention
- Sequela of bacterial meningitis
- Whipple disease
Viral
- Viral encephalitis (usually reversible)
  - Herpesviruses, including HSV-1, HSV-2, EBV, HHV-6, HHV-7 (and CMV and VZV, in immunocompromised people)
  - Arboviruses
  - Enteroviruses
- HIV-associated dementia: motor slowing, depressed mood, impaired recall but not recognition, poor visuospatial skills, and impaired executive function
  - Also, HIV-associated opportunistic infections including toxoplasmosis, cryptococcus, and CMV
- Hepatitis C virus
- Measles (subacute sclerosing panencephalitis, SSPE)
Fungal
- Cryptococcus
Parasitic
- Neurocysticercosis (rarely)
Prion
- Creutzfeld-Jakob disease