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Disease Transmission 1. An Infectious Agent Virus-the smallest infectious agent. requires a living cell to reproduce and must live inside a host cell to multiply. Most commonly spread by blood and other body secretions like saliva and mucus. Most can be killed by disinfects or sterilants. Some vaccines are available. Antibiotics are ineffective. EX. hepatitis, AIDSBacterium- single celled microorganisms that live inside tissues rather than specific cells in the body. Characteristics include cocci (round), bacilli (rod shaped), spirilla (spiral shaped), vibrios (curved). Either gram-negative or pram-positive. May form spores (hard protective covering that are resistant to chemical disinfectants). Not all are pathogenic. They reproduce in colonies, pairs, clusters or chains. Some immunizations are available, antibiotics are effective. Aeroic (need oxygen), anaerobic (only live in the absence of oxygen), facilitative anaerobe (can line/ live with or w/o oxygen). EX. TB, diphtheria, pertussis, tetanus, strep throat, staph infections, anthrax, dental caries, periodontal disease.Fungi- yeast and molds, are larger than bacteria. Some produce spores (difficult for heat and chemicals to penetrate and cannot be killed with antibiotics. May be treated with anti-fungals (topical or oral). EX. Candidiasis (thrush), tinea (athletes foot)Protozoa- single-celled animals often called amoeba, reproduce by binary fission/mitosis. Live in fluids in the bloodstream, the oral cavity, the intestinal tract, stagnant ponds and polluted water. EX. Amebic dysentery, malariaRickettsiae- similar to tiny bacteria in appearance, parasites. multiply inside the host and then the host transmits the disease to humans. lice, ticks, fleas, roaches, rats and mice are common hosts.EX. Rocky Mountian spotted fever, typhus. 2. A Reservoir where the invading organism lives and multiplies. may be inanimate matter, an insect (vectors), human cells, or blood. EX. soil is reservoir for tetanus3. A Mode of Escape or Portal of Exitport of exit from the reservoir, exit the body through various systems. escape from the bloodstream, may be through skin abrasions, hypodermic needles or dental instruments4. A Mode of Transmission patient to clinician, clinician to patient, patient to patient. Direct Contact- transmission is by touching an infected individual. EX direct contact with infected, blood, serum or salivaIndirect Transmission- transmission of microorganisms via an intermediary vehicle (inanimate object)airborne transmission- pathogenic microorganism is inhaled into susceptible host's  respiratory system. Dust-borne organisms- travel in dust brought to the dental environment from outside, surface disinfection of all equipment contacted during appointment helps control. EX. clostridium tetani, staphylococcus aureus. Aersols- less than 50 microns in diameter, occur in solid or liquid form, may be breathed deep into the lung and trapped in the respiratory tree. may contain pathogenic organisms, traces of mercury or amalgam. Splatter- heavier, larger particles. only airborne for a short period of time due to size and weight, may be visible, drop on objects, people and floor. Created during breathing speaking, coughing or sneezing. Contains microorganisms, particles from cavity prep, oil from hand piece, water from cooling equipment. ultrasonic scaling procedures create significant amount of aerosols. Move with air currents. Prevention- postpone elective treatment for patients with known communicable disease. Preoperative oral hygiene measures (brushing, flossing, antiseptic mouth rinse). Interruption of transmission (use of rubber dam, high volume suction), air quality control (adequate ventilation), clean dental environment (dust and vacuum) ran water through tubing's, protective mask and eye wear for clinician and patient. 5. A Mode or Portal of Entry port of entry from the reservoir, enters the body through various systems.  from the bloodstream, may be through skin abrasions, hypodermic needles or dental instruments6. A Susceptible Host Individual is unable to resist the pathogenic microogranism often related to the presence of other disease, immunosupression, surgical procedures, trauma, and absence of immunity.

Factors Influencing the Development of Infections number of pathogens virulence of the organism (how invasive) duration of the exposure general physical condition of the host general psychological status of the host the occupation or lifestyle environment of the host the presence of underlying diseases or conditions the age of the host.

Factors that Alter Normal Defenses1. abormal physical conditions: (congential or acquired) EX. defective heat vavlve 2. systemic disease: EX diabetes, alcoholism, AIDS3. Drug Therapy: (steriods, chemotherapeutic agents)4. Prothesis and Transplants: (Joint replacement, cardia prosthesis, organ transplant)

Disease Transmission