Climate change and globalization has led to an increase in pathogen load, diversity, and transmissibility which provide increasing challenges to the immune system. Diagram shows the multiple bacterial, viral and fungal pathogens encountered through the respiratory and oral-gastrointestinal tract that can spread throughout the population. These pathogens require mobilization and persistence of immune responses at these sites to prevent their infection and dissemination throughout the body. Aging imposes further changes on the immune system, which diminishes protective capacity to new pathogens. The changing global environment imposes changes in the food supply leading to malnutrition, systemic metabolic changes and metabolic disease (left), along with worsening air quality due to pollutants and toxins we breathe (right). The cumulative effects of all of these stresses results in worse overall health of the population and reduced lifespan.