Post-exposure prophylaxis (PEP) is a medical treatment designed to prevent infection after potential exposure to a virus, such as HIV. It involves taking antiretroviral medications as soon as possible, ideally within 72 hours of exposure, and continuing the treatment for about 28 days. PEP is most effective when started promptly and is not a substitute for regular preventive measures. PEP is typically recommended for individuals who have had a high-risk exposure, such as unprotected sex or sharing needles. It is important to consult a healthcare professional to assess the risk and determine the appropriate course of action following potential exposure.