Microbiology Chapter 16: Disease and Epidemiology

Epidemiology

• The study of geographical distribution and timing of disease occurrence and transmission

- Not just infectious disease

Etiology

• Determining the cause of death

Morbidity

• Being diseased

Total morbidity

• Number of diseased people, no reference to population

Morbidity rate

• Number of disease individuals per 100,000 people

• Also can be written as a precent

Prevalence

• The number or proportion of individuals with a particular illness in a given population at a point in time (active infections)

Incidence

• The number or proportion of new cases over a given time in a given population during a period of time

Sporadic

• Disease appears occasionally and usually does not have a geographical concentration

- Ex: Tetanus

Endemic

• Consistently present at low levels in a particular geographical area

- Ex: Seasonal flu

Epidemic

• Larger than expected number of cases in a particular geographic region at a particular time

- Ex: SARS in 2002 China

Pandemic

• A world wide epidemic

- Ex: COVID-19

CDC

• Center for Disease Control (and Prevention)

• Mission: Protect the public from disease

• Head appointed by the White House

• Oversees the NNDSS

NNDSS

• “National Notifiable Disease Surveillance System”

• Monitors diseases considered to be a public health concern

• Controlled by the CDC

John Snow

• “Father of epidemiology”

• Proved that all cases of cholera during a 1854 outbreak could be tracked back to one contaminated pump

Observational Studies

• Subjects are not manipulated in any way

• Information is gathered by data or survey compilation

• Can only show association

Experimental Study

• Subjects are manipulated in some way

- Uses placebos

• Can show casualty

Reservoirs

• Can be living organisms or nonliving sites

- Nonliving: Soil or water

- Living: Poultry

Carriers

• An individual capable of transmitting a pathogen without showing symptoms of disease

• Subdivided into passive and active carriers

- Passive: Carriers that aren’t infected, dirty hands

- Active: Carriers that are infected but don’t show disease

Direct Transmission

• Done from person to person

Vertical Transmission

• Form of direct transmission

• From mom to child via

- Pregnancy, breast feeding, birth

Horizontal Transmission

• Form of direct transmission

• From person to person who aren’t mother and child

- Kissing, sex, touching

Droplet

• Form of direct transmission

• From the wetness of coughs and sneezes

Indirect Transmission

• Not person to person

- Normally involving fomites

Aerosols

• Very small droplets

Mechanical

• Vector of transmission

• The insect has the pathogen on it but is not infected by it

- When the insect contacts you it transfers the disease onto you

Biological

• Vector of transmission

• The insect is infected by a pathogen

- When the insect contacts you it transfers the disease onto you

WHO

• World health organization

• Monitors and reports infectious diseases worldwide

• Develops and implements strategies for disease mitigation

• Monitors emerging and reemerging diseases

Emerging Diseases

• Diseases that are unknown to humans or have increased in prevalence

Reemerging diseases

• Disease that humans thought have been contained but aren’t

Florence Nightingale

• Invented military medicine

• Compiled data on cause of mortality in soldiers