The World Health Organization has estimated that as many as 10% of the population worldwide may at some point experience at least one seizure. The percentage with active epilepsy is from 0.4% to 1%. From 40% to 65% of patients with HIV infection have been estimated to have some neurological involvement; the percentage reaches as high as 70% to 80% when post-mortem assessments are included. Estimates of the percentage of HIV-infected patients with seizure occurrence have varied widely, with one review finding a range from 2% to 20%. The highest percentage in this range was reported at a center that exclusively treated patients with neurological involvement, in India where HIV clade C subtype is predominant. Query of another neurology department's database determined that of the HIV-infected patients treated at the center, all of whom were referred for neurological symptoms, 6.1% experienced seizures. Underlying neurologic diseases in these patients included HIV-associated encephalopathy, progressive multifocal leukoencephalopathy, and toxoplasmosis. In a Spanish population, 3% of HIV-infected patients over a one-year study period were found to have new-onset seizures, which were attributed to drug toxicity in 47%, intracranial lesions in 35%, and metabolic derangements in 12%.