CrAg screening of severely immunosuppressed patients (typically with CD4 counts ≤100 cells/mm3), which is recommended by the WHO and the President's Emergency Plan for AIDS Relief (PEPFAR), combined with preemptive antifungal treatment can prevent or detect at an early stage a significant proportion of cryptococcal meningitis cases, as the antigen can be detected in blood for weeks to months prior to the development of clinical disease. The gene discussed is CD4; the disease is AIDS.