An epidemiologist is a professional who studies patterns and causes of health and disease conditions in populations. They use various research methods to investigate the factors that contribute to the spread of diseases, including studying the characteristics of individuals, communities, and environments. Epidemiologists work to identify risk factors for diseases, monitor and control outbreaks, and develop strategies to prevent future occurrences. Their findings can be used by public health officials, policymakers, and medical professionals to make informed decisions about disease prevention and treatment.