Ecological Niche Replacement: When a pathogen is suppressed, another pathogen that occupies a similar ecological niche may flourish. This is often seen in the context of antibiotic use where the suppression of susceptible bacteria leads to the proliferation of resistant strains. Immunological Replacement: Vaccines targeting specific strains of a pathogen may lead to the emergence of non-vaccine strains. For example, the introduction of pneumococcal conjugate vaccines has led to a decrease in vaccine-type strains but an increase in non-vaccine-type strains. Behavioral Factors: Changes in human behavior, such as increased hygiene practices reducing one disease, can sometimes lead to the emergence of other diseases that thrive in cleaner environments.
