Several factors contribute to selection pressure in epidemiology:
1. Treatment Interventions: The use of treatments, such as antibiotics or antiviral drugs, can create selection pressure by killing susceptible pathogens and allowing resistant ones to survive. 2. Host Immunity: Natural immunity or vaccine-induced immunity can exert selection pressure on pathogens, leading to the emergence of immune escape variants. 3. Environmental Changes: Changes in the environment, such as climate change or urbanization, can alter the selection pressure on pathogens by affecting their transmission dynamics. 4. Population Density: High population density can increase the transmission rate of infectious diseases, thereby influencing the selection pressure on pathogens to evolve higher virulence or transmission efficiency.
