Unit 3

the study of the distribution of disease or health conditions (what) and their determinants (how) in a given population (who) and location (where) during a specified period (when)

• rate of occurrence of new cases
• significance to disease rate - trend shows incr or decr - is health intervention program working

• total number of cases of disease in a population
• significance of disease rate - health resource allocation (pt f/u, education, treatment)

• randomly occuring cases
• e.g. flesh-eating disease (necrotizing fascilitis)

• low incidence
• persistent in a given location
• e.g. Lyme disease

• incidence exceeds historical number of cases (mean/median)
• e.g. seasonal flu epidemic

• world-wide/global epidemic
• e.g. 2009 H1N1 pandemic

• 1) high fever >38 (found in many disease)
• 2) pain disportional to size of wound (sometimes not visible)

• an illness that is caused by an infectious agent and/or its toxin that can be transimitted directly and/or indirectly via
• human to human
• animal to human

only infectious disease that has been eradicated from earth

eliminated in North America (elimination = polio free in a country/continent)

primary an animal disease that is transfered to humans

• poultry > salmonella
• birds > parrot fever, psittaccosis (resp infection > pneumonia)

resp infection > pneumonia

period of time during which an infected person can pass on the infection to other susecptible people

• 1 day before s/s appear
• (s/s 1-4 days after entering)
• 5-7 after becoming sick
• children can pass 7+ days

• IP: 28-30 days
• max infectivity occurs in latter half of IP continues a few days after jaundice onset

• virus disease
• IP = 2-10 days
• w/in 3ft / contact
• recent travel to Asia w/in 10 days + contact
• 10 days s/s is gone
• only inf. when s/s visible but take precautions

• bacterial disease
• fecal-oral route
• pass stool + urine that is infected up to 3 months!
• 2-5% chronic carriers

• degree of contagiousness
• depends on POC - (a) contact rate + (b) time allowed for spread of infection
• e.g. asymptomatic infection

• the # of new cases that can be produced by an infected person w/ a particular infection
• R₀ > 1 in order for an epidemic to occur
• R₀ < 1 = no epidemic
• greater R₀ = more contagious

• 1) vaccine only has 3 strains (2 Type A + 1 Type B) (circulating strain doesn't mean vaccine strain)
• 2) flu like symptoms doesn't mean flu
• 3) already infected
• 4) vaccine does not contain live virus