Module 42Differentiate the distribution of endemic, epidemic, and pandemic diseases - Endemic: always present in the population but at a low level- Epidemic: outbreak of a disease in one area- Pandemic: widespread outbreak in a wide areaExplain how mortality and morbidity are calculated Number of deaths due to a disease divided by the populationReview the stages of a chronic infection 1. Infection is not totally eradicated.2. Organism continues to reproduce in body. Clinical signs are present and usually milder than in acute infection.3. Periodic acute episodes may recurDescribe what an epi curve is and how it is interpreted an epidemic curve is a plot that shows the number of cases over the time of onset of illness using appropriate time intervalDifferentiate between common source and host-to-host transmission and what their epi curves look like -common source is when a single source infects many individuals in a short period of time (cholera)Usually result of contaminated food/ water Epi curve is spiked where the epidemic occurred, short lived -host to host transmission has a slower increase in cases (influenza) Transmission from infected host to another uninfected host takes time Pathogen must replicate in each newly-infected host before it can be transmitted to another Epi curve is gradualExplain R0 and interpret if the value is >1, <1, or =1. - Population increasing- Population decreasing- Population stableDescribe what stage of acute infections when infected individuals can transmit pathogens toothers Through direct host-host transmissionBe able to describe a chronic infection, and what “subclinical symptoms” mean Chronic infection: is a persistent, long-lasting disease that can last months or years. Symptoms are mild to nonexistent (subclinical)Differentiate between fomites and vectors - Fomites are intimate objects that can harbor pathogens (pathogen has to be able to survive in the environment)- vectors are live agents that can transmit pathogens (insects: ticks, mosquito. pathogen has to be able to survive inside a vector)Recognize and interpret an epi curve for seasonal and a common source epidemic - Seasonal epic curves occur when infections only occur at certain times of the year (certain seasons have spikes)- common source epic is when a single source infects many individuals in a short time (one quick spike)- host-to-host is very gradual infection timelineDescribe, or sketch a graph (R0vs percent herd immunity), of how basic reproduction number is related to the level of a population’s herd immunity that is required to prevent outbreaks The higher the Ro for a specific disease, the greater the herd immunity required to prevent spread. The goal is disease transmission control in is to reduce the Ro for a pathogenDescribe the difference between reservoirs and carriers Reservoirs: places or populations that contain infectious agents capable of infecting susceptible individualsCarriers: are infected individuals with mild or no symptoms that are capable of infecting other susceptible individualsExplain how vehicle control, vector control, reservoir control, and quarantine help prevent outbreaks.-Vehicle control: eliminates many common source diseases. Sewage and wastewater treatment and treatment of distributed water -Vector control: reducing contact of vectors with susceptible populations Mosquito spraying/nets to reduce the number of malaria, yellow fever. Control of ticks (Rocky Mountain spotted fever, lyme disease)-Reservoir control: eliminating (rare) or vaccination of reservoir populations Immunization of domestic animal populations against rabies Elimination of rats to reduce plague -Quarantine: the isolation of possible disease carriers until a disease-free state can be assured. All mammals entering rabies-free Australia must be quarantined to make sure they do not have rabies
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