Microbio Final: Week 12

Epidemiology

Epidemiology

the study of where and when diseases occur and how they are transmitted in populations

Chain of Infection

organism = reservoir = transmission = susceptible host

John Snow

tracked the source of a cholera outbreak in London in 1854 to water from a specific well

ended the outbreak by breaking the chain of transmission

Ignaz Semmelweis

showed that handwashing decreased the incidence of puerperal sepsis

Florence Nightingale

showed that improved sanitation decreased the incidence of epidemic typhus

Role of Epidemiology

determine etiology of a disease

identify other important factors and patterns concerning the spread of disease

assemble data and graphs to outline incidence of disease

predict the probability that an infection will spread through a population

explores various methods for controlling a disease

reproductive number

Reproductive Number

average number of people who will contract a disease from one infected individual

Descriptive Epidemiology

collection and analysis of data

ex: snows search for the source of cholera outbreak

Analytical Epidemiology

analyzed a particular disease to determine its probable cause or risk factors

ex: nightingales work

Experimental Epidemiology

involves a hypothesis and controlled experiments

ex: semmelweis

Clinical Trial

test and control group

Case Reporting

enables researchers to establish the chain of transmission

requires health care workers to report specified diseases to local, state, and national health officials

notifiable infection diseases list

provide early warning of possible outbreaks

Center for Disease Control and Prevention (CDC)

collects and analyzed epidemiological information in the united states

publishes morbidity and mortality weekly report (MMWR)

morbidity: incidence of a specific notable disease

mortality: deaths from a notable disease

articles include reports of disease outbreaks, case histories, and summaries of the status of an particular disease

Notable Infectious Diseases

diseases in which physicians are required to report occurence

Morbidity Rate

number of people affected in relation to the total population in a given time period

Mortality Rate

number of deaths from a disease in relation to the total population in a given time period

Sporadic Disease

disease that occurs only occasionally

Endemic Disease

disease constantly present in a population

Epidemic Disease

disease acquired by many people in a given area in a short time

Pandemic

worldwide epidemic

Incidence

number of people who develop a disease during a particular time period

number of new cases of a disease in that population

Prevalence

number of people who have a disease at a specified time regardless of when it first appeared

total number of active cases of a disease in a population

takes into account both old and new cases

Common Source Epidemics

a way to classify a major epidemic

usually arises from contamination of water or food

ex: cholera

Host to Host Epidemic

a way to classify a major epidemic

the disease shows a slow, progressive rise or gradual decline

ex: influenza and chicken pox

HIV and Reemerging Disease

global spread has increased number of immunocompromised persons, allowing for reemergence of some infectious diseases once thought to be under control

immunocompromised patients are highly susceptible to infections including mycobacterium tuberculosis which has reemerged as drug development

Disease Tracking

for epidemics: find the index case or patient zero (first person with disease) and then identify all people who had contact with the individual

Obstacles of Global Surveillance

not every country has modern clinical laboratories, efficient case reporting, effective political systems to detect and limit outbreaks of infectious disease

resources of developing countries are too limited to reach public health goals

CDC and WHO mobilize teams of scientists and medical personnel, sending them to remote parts of the world when global health is threatened

Quarantine and Isolation

applied to healthy people exposed to a disease during the incubation period

limits the movements of such people and not necessarily to precautions during treatment

Notifiable Diseases

infectious diseases that are potentially harmful to the publics health and must be reported by physicians

Lyme Disease Agent

borrelia burgdorferi

Lyme Disease Mode of Transmission

bite of infected ixodes tick

Lyme Disease Cause of Emergence

increase in deer and human populations in wooded areas

Tuberculosis Agent

mycobacterium tuberculosis

Tuberculosis Mode of Transmission

sputum droplets (exhaled through a cough or sneeze) from a person with active disease

Tuberculosis Cause of Emergence

antimicrobial drug resistance as multidrug resistant and extensively drug resistant bacterium

Antibiotic Associated Enterocolitis Agent

clostridioides difficile

Antibiotic Associated Enterocolitis Mode of Transmission

person to person contact and through fomites in healthcare settings

Antibiotic Associated Enterocolitis Cause of Emergence

gut dysbiosis due to long term use of antibiotics

Cholera Agent

vibrio cholerae, causes severe diarrhea and rapid dehydration

Cholera Mode of Transmission

water contaminated with feces of infected people, food exposed to contaminated water

Cholera Cause of Emergence

poor sanitation and hygiene, carried to non endemic areas via affected travelers and commerce

Hemorrhagic Fever Agent

dengue

Hemorrhagic Fever Mode of Transmission

bite of an infected mosquito, primarily aedes aegypti

Hemorrhagic Fever Cause of Emergence

poor mosquito control, increased urbanization in tropics and increased travel and shipping

Pneumonia Agent

influenza H5N1 - avian influenza, causes fever, headache, and cough

Pneumonia Mode of Transmission

direct contact with infected animals or humans, not easily spread via respiratory aerosols

Pneumonia Cause of Emergence

danger of animal-human virus reassortment, antigenic shift

Zika Symptoms

asymptomatic or fever, rash, muscle and joint pain

Zika Mode of Transmission

bite of an infected mosquito (primarily aedes aegypti), mother to fetus, sexual contact, or blood transfusion

Zika Cause of Emergence

poor mosquito control increased urbanization in tropics