Disease Patterns and Epidemiology Nestor T. Hilvano, M.D., M.P.H.

Learning Objectives 1.Distinguish the 3 types of symbiosis between microbes and their hosts. 2.Describe three conditions that create opportunities for normal microbiota to cause disease. 3.Describe the portals through which pathogens invade the body. 4.Contrast symptoms, signs, and syndromes. 5.List and describe the five stages of infectious diseases. 6.Describe three types of reservoirs of infection in humans. 7.Distinguish among acute, subacute, chronic, and latent diseases. 8.Distinguish among communicable and noncommunicable infectious diseases. 9.Define epidemiology and contrast between incidence and prevalence. 10. Differentiate the terms endemic, sporadic, epidemic, and pandemic. 11. Describe three types of nosocomial infections, factors that influence their development, and how they may be prevented. 12.List how public health agencies work to limit the spread of diseases.

Symbiotic Relationships Symbiosis= living together Mutualism – both members benefit ex. enteric bacteria (in gut) aid food digestion in host, host uses digested food as energy source Parasitism – parasite benefits, host harmed ex. parasitic worms, cholera, or giardia causing disease in human; protozoa feed on mucosa causing ulcer and dysentery Commensalism – one member benefits, the other (host) unaffected ex. normal microbiota are mostly commensal; bacteria that consume dead skin without harming the host

Ways Normal Microbiota become Opportunistic Pathogens Immune supression – disease, malnutrition, physical or emotional stress, extremes of age, use of radiation or chemotherapy, use of immunosupressive drugs Changes in normal microbiota – microbial antagonism or competition Introduction of normal microbiota into an abnormal site in the body

Portal of Entry of Invading Pathogens ___ is the invasion of a pathogen. ___ results when pathogen adversely affect the body. a.Infection b.Disease

Manifestations of Disease Symptoms – subjective characteristics ex. pain, headache, itchiness Signs – objectively observable and measurable ex. fever (39°C), swelling, yellowish discoloration of skin (Jaundice) Syndrome – group of signs and symptoms

5 Stages of Infectious Diseases ___ silent stage, the pathogen gains entry into the host & starts replicating. ___ the first onset of S/Sx, usually lasts about 1 or 2 days. ___ the disease reaches it’s highest point of development (acute stage). ___ the symptoms start to subside, the infection is still present but pt. health starts to return to normal. ___ the symptoms vanished completely and the pathogen has been mostly eliminated, pt. return to original state of health. a. Declining stage b. Incubation stage c. Convalescence stage d. Illness stage e. Prodromal stage

Sources of Infectious Diseases and MOT Sources 1.Animal reservoirs- zoonosis 2. Human carriers 3.Nonliving reservoirs MOT 1.Contact – direct (person to person); indirect (fomites); droplet transmission 2.Vehicle – water, food, fluids, air 3.Vector – arthropods (biological or mechanical)

Infectious Diseases Communicable- disease transmitted from one host to another host; Ex: Influenza * contagious- communicable disease that is easily spread; Ex: Chickenpox Non-communicable- disease arising from outside of host or from opportunistic pathogen; tooth decay; acne; tetanus

Epidemiology and Frequency of Disease __________ is the study of location, course, and transmission of diseases within populations. Incidence Prev alence Why does an incidence of a disease never exceed the prevalence of that disease?

Occurrence of Diseases ___ - is normally present in a region. ___ - occurs irregularly and infrequently. ___ - is present in greater frequency than is usual. ___ - is an epidemic disease occurring on more than one continent at a given time. a. pandemic b. epidemic c. sporadic d. endemic

Epidemiological Studies Descriptive epidemiology – recording of data Analytical epidemiology – det. probable cause, MOT, and prevention Experimental epidemiology – testing hypothesis

Types of Nosocomial Infections 10% of American patients (2 bil.) acquire nosocomial infections each year 90,000 deaths annually in US Exogenous – from health care environment Endogenous – from normal flora that become opportunistic Iatrogenic – caused by treatment or medical procedures

Role of Public Health to limit spread of disease Share epidemiological data to promulgate rules and standards in public health safety – reports on incidence and prevalence; conduct research in disease etiology and prevention Enforce safety standards to limit disease transmission – clean water and food supplies; control vectors and animal reservoirs Public health education – to make healthful choices in preventing disease

Homework 1.Define terms: pathogen; infection; disease (morbidity); acute disease; subacute disease; chronic disease; latent disease; communicable disease; noncommunicable disease; contagious; mutualism; parasitism; commensalism; sign; symptom; syndrome 2.Describe the manner of transmission of infectious diseases in human. 3.Define epidemiology and describe the types of occurrence of disease in a particular population. 4.Discuss the 5 stages of infectious disease.