Epidemiology: Prevention and Control of Diseases and Health Conditions Chapter 4
Introduction Disease classification can lead to prevention and control. In community health, classification is usually Acute or chronic (<3 or >3 months) Communicable (infectious-caused by a specific biological agent/pathogen) or noncommunicable (noninfectious-cannot be transmitted from one person to another)
Classification of Diseases
Communicable Diseases Infectivity: ability of a biological agent to enter and grow in the host (biological agents include viruses, rickettsiae, bacteria, protozoa, and fungi) Agent: the element that must be present for disease to occur. (exp: the influenza virus must be present for a person to become ill with flu) Host: any susceptible organism (human, animal, plant) Environment: factors that inhibit or promote disease transmission
Biological Agents of Disease
Chain of Infection Step by step model to conceptualize the transmission of a communicable disease from its source to a susceptible host
Chain of Infection Pathogen: disease causing agent (virus, bacterium, etc.) Reservoir: favorable environment for infectious agent to live and grow (human, animal, plant, etc.) Portal of exit: path by which agent leaves host (blood, respiratory system, digestive system, etc.)
Chain of Infection Mode of transmission: how pathogens are passed from reservoir to next host Direct transmission touching, biting, kissing, sex, or droplet spray (sneeze, coughing, etc.) Indirect transmission airborn, vehicleborne, vetctorborne. Portal of entry: where agent enters susceptible host (blood, respiratory or digestive system, etc.) New host: susceptible to new infection being established
Chain of Infection Example Agent (cold virus), leaves reservoir (throat of infected person), when host sneezes (portal of exit-nose and mouth). Direct transmission (saliva droplets) enter respiratory tract of susceptible host at close range (portal of entry-mouth). New infection possibly established. (www.miniclip.com/games/sneeze) If one link is missing, chain is broken
Direct transmission Modes of Transmission Immediate transfer of disease agent between infected and susceptible individuals Touching, biting, kissing, sexual intercourse Indirect transmission Disease transmission involving an intermediate step Airborne, vehicleborne, vectorborne, biological
Transmission Vectors include: mosquitoes, flies, lice, ticks, flies, and other insects. Mosquitoes are by far the most important vectors of human disease. Yellow fever West Nile virus Malaria Over 200 other viruses.
Noncommunicable Diseases Although non-communicable diseases are not infectious, they can occur in epidemic proportions. They can deplete a community s resources quite rapidly. Nation s leading causes of death Heart disease, stroke, cancer Chronic obstructive pulmonary disease Diabetes Alzheimer s disease
Prioritizing Prevention and Control Efforts Criteria used to judge importance of disease to a community # of people who will die from a disease Leading causes of death # of years of potential life lost Captures issues affiliated with various groups Economic costs associated with disease $ spent at various levels of government; ex: alcohol and other drugs
Prevention, Intervention, Control and Eradication of Diseases Prevention: planning for and taking action to prevent or forestall onset of disease or health problem Intervention: effort to control disease in progress; taking action during an event Control - Containment of a disease; prevention and intervention measures Eradication: total elimination of disease from human population
Primary Prevention of Communicable Diseases Strategies at each link in chain of infection Individuals Hand washing, using condoms, properly cooking food Communities Chlorinating water supply, inspecting restaurants, immunization programs for all citizens, vector control, solid waste disposal
Individuals Self-diagnosis, self-treatment w/home remedies Antibiotics prescribed by a physician Communities Secondary Prevention of Communicable Diseases Controlling or limiting extent of an epidemic Carefully maintaining records; investigating cases Isolation, quarantine, disinfection
Individuals Recovery to full health after infection; return to normal activity Communities Tertiary Prevention of Communicable Diseases Preventing recurrence of epidemics Removal, embalming, burial of dead Reapplication of primary and secondary measures
Individuals Primary Prevention of Noncommunicable Diseases Education and knowledge about health and disease prevention, eating properly, adequate exercise, driving safely Communities Adequate food and energy supplies, efficient community services, opportunities for education, employment, and housing
Individuals Secondary Prevention of Noncommunicable Diseases Personal screenings (mammogram, pap test, PSA test), regular medical and dental checkups, pursuit of diagnosis and prompt treatment Communities Provision of mass screenings for chronic diseases, case-finding measures, provision of adequate health personnel, equipment, and facilities
Individuals Tertiary Prevention of Noncommunicable Diseases Significant behavioral or lifestyle changes, adherence to prescribed medications, following rehabilitation requirements after surgery Communities Adequate emergency medical personnel and services: hospitals, surgeons, nurses, ambulance services
Diseases of the Heart & Blood Vessels Cardisovascular Diseases (CVD s) In 2008 alone, more than 617,520 people died of heart disease in the US. One in four deaths that year. The behavior patterns that contribute to the risk of heart disease is: Tobacco use poor diet Physical inactivity
Size The heart is a fist-sized muscle with four chambers: the right & left atria and the right and left ventricles.
Right side of the heart Pulmonary Circulation Pumping oxygen-poor blood (deoxygenated) to the lungs and oxygen-rich blood back to the heart.
Systemic Circulation Left side of the heart Pumping oxygen-rich blood to the rest of the body and returning oxygen-poor blood to the heart. (Comes in to the right side of the heart) http://www.youtube.com/watch?v=ohmmtqkgs50
Heart Vena Cava Largest veins in the body that carry deoxygenated blood from the body back to the heart. Aorta Largest artery in the body- branches into smaller arteries and capillaries carrying oxygen rich blood to body tissues. Coronary arteries Medium-sized arteries that supply blood to the heart muscle.
Heartbeat The contraction and relaxation of the ventriles is what we feel and hear as the heartbeat. (Blood pressure) Systole contraction phase Diastole Relaxation phase Average heartbeat = 70/minute (60-80)
Starts at a young age. Atherosclerosis A harding of the arteries due to buildup of fats, cholesterol, calcium & other substances in artery walls. Fatty streak in an artery
Lipoprotein The fatty streaks consist of an accumulation of lipoproteins (fat molecules with phosphate groups chemically attached) and cholesterol (a waxy, fatlike substance) Lipoproteins are packages that carry cholesterol and fats through the bloodstream.
Plaque When the artery wall is damaged (by tobacco, high blood pressure, or infection) it can create a lesion. The lipoproteins accumulate within the wall. Plaque causes the artery wall to enlarge and bulge. Plaques can break off and completely block the artery. Heart attacks, strokes, and peripheral vascular disease are all consequences of this.
Coronary Heart Disease When artherosclerosis involves a coronary artery, the result is Coronary heart disease (CHD) and often a heart attack. If the artery is at least 70% to completely blocked, the person may have a Myocardial infarction or heart attack.
Thrombus Is when blockage breaks loose causing a blood clot. Blood clots can also for in a damaged artery related to surgery or injury. This condition is called a coronary thrombosis and can cause sudden death.
Signs of a heart attack Chest discomfort mostly in the center of the chest Discomfort in other areas of the upper body arms, back, neck Shortness of breath Cold swat, nausea, or lightheaded
Stroke When blood flow to the brain or part of the brain is blocked. (CVA) Cerebrovascular accident or stroke. Ischemic strokes 87% of all strokes Occur when an artery in the brain becomes blocked. Preventing the brain from receiving blood flow. A blockage due to a thrombus (blood clot)
Blood Pressure Blood Pressure force exerted by the blood against artery walls. Hypertension Blood pressure that is forceful enough to damage artery walls. Once again systolic pressure the upper number the pressure produced when the heart contracts. Diastolic pressure lower number the pressure in the arteries when the heart is relaxed, between contractions.
http://www.youtube.com/watch? v=dig519dfvns You-tube high blood pressure