Section 22.6 Hosts and pathogens coevolve with time, and arrive at a steady rate that favors the continued survival of both. With herd immunity, a large fraction of a population is immune to a given disease, and it is difficult for the disease to spread. Disease cycles occur when a large, recurring, nonimmune population, such as children entering school, is exposed to a pathogen. Explain coevolution of host and pathogen. Cite a specific example.
Many common microorganisms have the potential to be pathogens in a hospital environment.
Hospital patients are unusually sensitive to infectious disease, and are exposed to a variety of potential pathogens, including opportunistic pathogens, in the hospital environment. Antibiotic resistance complicates treatment of these infections. Section 22.8 Food and water purity regulations, vector control, immunization, quarantine, disease surveillance, and eradication are public health measures that play a major role in reduction of disease incidence. Compare public measures for controlling infectious disease caused by insect reservoirs, and by human carriers. Section 22.9 Infectious diseases account for over one third of all worldwide mortality.