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University of Toronto Scarborough
Health Studies

HLTA01H3 Chapter 1 The Nature of Plagues1192012 112400 AM Disease can be a personal affair pneumoniaLegionnaires disease air was implicated as the probable pathway of spread of the disease and the most popular theory was that infection resulted from aspiration of bacteria called Legionella in aerosolized water from either cooling towers or evaporative condensersUnlike infections caused by inhalation inhalation means entry of disease during respiratory aspiration is produced by choking Secretions in the mouth get past the choking reflex and instead of going into the esophagusand stomach mistakenly enter the lungs The outbreak of Legionnaires disease have been traced to water heaters whirlpool baths respiratory therapy equipment and ultrasonic misters used in grocery storesToxic shock syndrome TSS the source of Marys infection and the possibility that it might be spread thru the population as a sexually transmitted disease STDTSS is a gender specific disease However TSS was note an STD it linked to the use of certain types of tampons especially those containing crosslinked carboxymethyl cellulose with polyester foam which provided a favorable environment for the toxinproducing S aureus The symptoms of TSS are begin with vomiting and high fever followed by lightheadedness and fainting the throat felt sore and the muscles ached A day later a sunburnlike rash appeared and the eyes became bloodshot Within 34days victims suffered confusion fatigue weakness thirst and a rapid pulse the sin became cool and moist and breathing became rapid This was followed by a sudden drop in blood pressure if it remained low enough for a long enough period circulatory collapse produced shockThe effects of disease at the personal level can be tragic but when illness occurs in many people it may produce another emotionfear for now the disease might spread rapidly Our world is much more vulnerable than it was in the past New and old diseases can erupt and spread throughout the world more quickly because of the increased and rapid movements of people and goods Eg the efficiencies in transportation fast moving ships trains and planesNew diseases may be related to advances in technology eg TSS resulted from the improved menstrual tampons Legionnaires disease was the result of the growth and spread of germ thru the hotels airconditioning systemIncubation period interval of time required for development of a disease Latent period seemingly inactive period between exposure to an infection and subsequent illness Parasite virulence capacity of a parasite to cause disease Zoonotic infections animal infections that can be transmitted to humansThe germs that caused SARS Legionnaires disease and TSS are parasites Parasites some entities are unable to survive on their own and require another living being for their nourishment These lifedependent entities that feed at the table of the richfrom the Latin word parasitus meaning food Some parasites such as tapeworms hookworms the malaria parasite HIV live inside the body whereas others ticks and chiggers live on the surface Parasites are invariably smaller in mass than their host Parasites often harm their host However they will not always kill their host this is because resistance may develop in any population of hosts and not every potential host will be infectedsome individuals may be immune or not susceptible because of a genetic abnormality or the absence of some critical dietary factor Some parasites have complex life cycles and may have several hosts eg malaria the hosts are mosquitoes and humans Parasites produce lots of offspring thereby increasing the odds that some will reach new hosts More offspring will have a greater probability o reaching a host and setting up an infection Then m the parasite enhances its chances for survival eg malaria parasite the red blood celldestroying hookworms and the white blood cell killer HIVThe movement of a parasite from host to hostwhether by direct or indirect means is called transmission When the transmission of parasites involves living organisms such as flies mosquitoes fleas lice or snails these animate intermediaries are called vectorsTransmission by a vector may mechanical or developmental or contamination of eating utensilsdrinking cups food bedclothes towels or clothing or in droplet secretions Parasite and their freeliving relatives come in a variety of sizes shapes and kinds or species eg bacteria and virus are called micro parasites Larger parasites that can be seen without the use of a microscope are referred to as macro parasites they are composed of many cells Virus although a viruss genetic code contains all the info needed for assembling a new virus it lacks that which is necessary for reproduction So for a virus to reproduce it must enter a living cell and use the cellular machinery to replicate itself Viruses are not completely independent they are not alive and yet they can be killed if their DNA or RNA is destroyed Virus are neither cells nor organisms they are called infectious microbes or germs Bacteria are independent existence Bacteria do not need a host to reproduce they can be either free living or parasiticPlagues all diseases outbreaks irrespective of their cause When a parasite invades a host it establishes an infection and wounds the body Contagious are contagious before symptoms appear has a short incubation period and infrequently requires hospitalization eg normal fluinfectious infectious only after symptoms appear longer incubation period and hospitalization required eg SARSinfectiousness may persist even after disease symptoms have disappeared the person who are infectious but asymptomatic are called carrier Forecasting Storms prediction Plagues Three factors are required for a parasite to spread from host to host 1 there must be infectious individuals 2 there must a susceptible individuals and there must be a means for transmission between the two
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