Infectious Disease - Occurrence of Infectious Diseaseo Incidence = portion of the population that contracts a disease during a specific time  NEW cases o Prevalence = portion of the population that has a disease during a specific time  TOTAL cases o Sporadic diseases = disease that occurs occasionally in the population o Endemic diseases = disease constantly presents in population o Epidemic diseases = disease acquired by many hosts in a given area in a short timeo Pandemic diseases = worldwide epidemic  However, does not indicate the severity of the disease, just the spread  Example: 1918 Influenza Pandemic - Reservoirs of Infectiono Humanso Animalso Environmental Water and soil - Transmissionso Direct contacto Droplet transmission o Indirect transmission  Fomites  Example: doorknob - Vehicle Transmissiono Transmission by inanimate reservoir o Aerosols o Food  Fecal-oral transmission- Vector-borne Diseases o Arthropods  Fleas, ticks, mosquitoso Mechanical Transmission o Biological Transmission- Nosocomial Infections o Hospital acquired infections (HAI)o Multiple Factors Microbes in the hospital  Compromised host Chain of transmission - Usually the health care workero Examples UTIs, surgical site, lower respiratory, GI, bloodstream Breaches body’s natural barriers - Emerging Infectious Diseaseso Genetic recombinationo Evolution of new stains o Misuse of Antibiotics o Climate changeo Globalization o War or Natural Disasters o Animal Controlo Public Health Disaster- Outbreak Information o Etiology o Reservoir o Mode of transmission o