Final answer:
The DoD Periodic Health Assessment begins with observations to evaluate a service member's health, which is essential for identifying potential health issues. Agencies like the CDC use surveys to collect population health data, and the stages of disease include periods where patient symptoms and pathogen levels change.
Step-by-step explanation:
The first process of the Department of Defense (DoD) Periodic Health Assessment involves observations, where health professionals evaluate the service member's health status through direct physical examination and historical health data collection. This phase sets the stage for identifying any medical issues that need to be addressed.
Health agencies, such as the Centers for Disease Control and Prevention (CDC), collect data on the incidence of diseases by using tools like the Behavioral Risk Factor Surveillance System (BRFSS), which includes questions on overall health status and the number of poor health days. The answers help to establish baseline data for a region's health. The stages of disease include various periods, such as the period of illness and the period of decline.