Disease and Epidimeiology

Pathology

Study of disease

Etiology

Study of the cause of disease

Pathogenesis

Manner in which a disease developes

Infection

Invasion/colonization of the body by pathogens

Infectious Disease

Disease when infection results in change of state of health

When does the human microbiome gets established?

Begins in utero and keeps developing for the first 10 years of life

How many bacterial cells does the human microbiome have?

4×10¹³

Human Microbiome Project

Analyzes relationships between microbial communities on body and health

Normal Microbiota / Normal Flora

Permanently colonize host and does not cause disease

Transient Microbiota

Temporary microbes that can be present for days, weeks, months

Hygiene Hypothesis

Insufficient exposure to microbes in childhood may interfere with development of immune system

Microbial Antagonism / Competitive Exclusion

Competition between microbes ; ex. competing with invading microbes for nutrients

Ways normal microbiota protect host :

• Competing with invading microbes for nutrients

• Produce substance harmful to invaders

• Affecting pH and available oxygen

Commensalism

One organism benefits and the other unaffected ; ex. Staphylococcs epidermis

Mutualism

Both organism benefits ; ex. E-coli

Parasitism

One organism benefits at expense of the other ; ex. influenza

Koch’s Postulates

A set of criteria established to demonstrate the causative relationship between a microorganism and a disease

Symptoms

Changes in body function that are felt by patient as a result of the disease ; not apparent to observer

Signs

Changes in body that can be measures/observed as a result of disease

Syndrome

Specific group of signs/symptoms that accompany a disease

Communicable Disease

Disease that is spread from one host to another ; ex. influenza

Contagious Disease

Disease that are easily and rapidly spread

Noncommunicable Disease

Disease that does not spread from one host to another ; ex. tetanus

Incidence

Number of people who develop a disease during a particular time period ; number of new cases/period of time

Prevalence

Number of people with the disease at a specific time, regardless of when it first appeared ; all cases of disease/period of time

Sporadic Disease

Occurs occasionally

Endemic Disease

Constantly present

Epidemic Disease

Acquired by many in given area in short time

Pandemic Disease

Worldwide epidemic

Duration

Average time someone have the disease from diagnosis to being cured/death

Acute Disease

Develop rapidly, but short duration

Chronic Disease

Develop slowly and can last for a while

Subacute Disease

Lasts longer than acute disease but does not last as long as chronic disease

Latent Disease

Inactive for a while, but then activates

Severity

Presence and extensiveness of a disease in the body

Infection Fatality Ratio

Assess severity of disease ; number of deaths/infected

Case Fatality Ratio

Proportion of individuals diagnosed who die within certain time period

Local Infection

Invading microbes limited to small area

Systemic Infection

Invading microbes spread throughout body

Focal Infection

Local infection enters blood/lymph and spread to another area where it gets confined

Primary Infection

Acute infection from initial illness

Secondary Illness

Infection caused by opportunistic pathogen after body is weaken by primary infection

Predisposing Factors

Variables that make your body more susceptible to disease or alter course of disease

Incubation Period

Period between initial infection and first signs/symptoms

Prodromal Period

Short period after incubation; mild non-specific symptoms

Period of Illness

Disease most severe

Period of Decline

Signs/symptoms subside

Period of Convalescence

Body returns to pre-disease state ; recovery

Human Reservoirs

People with signs/symptoms

Reservoirs

Continual source of the pathogen ; somewhere with adequate conditions for survival, multiplication, and opportunity for transmission

Carriers

Host with the infection, but shows no signs/symptoms

Zoonoses

Disease primarily in wild/domestic animals that can be transmitted to humans

Nonliving Reservoir

Soil, water, food

Direct Contact

Requires close association between infected and host

Congenital Transmission

From mother to newborn/fetus at birth

Indirect Contact Transmission

Spreads to host by nonliving object (fomite) ; ex. student sneeze on work, teacher grades work, teacher gets sick

Droplet Transmission

Airborne droplets <1 meter

Vehicle Transmission

Air, water, food ; may involve cross-contamination

Nosocomial Infection

Healthcare-associated infection (HAIs) ; infection acquired in healthcare setting

Leading cause of HAIs

Clostridioides difficile

Universal Precaution

Designed to reduce transmission of microbes in healthcare ; standard and transmission-based

Standard Precaution

Basic, minimum practices ; hand hygiene, PPE, cleaning, etc

Transmission-based Precaution

For infections that are highly transmissible or epidemiological important pathogens ; contact, droplet, airborne precautions

Epidemiology

Study of where and when diseases occur and how they’re transmitted

Center of Disease Control and Prevention (CDC)

Collects and analyze epidemiological info in the US

Notifiable Infectious Disease

Disease in which physicians are required to report occurance

Morbidity

Incidence of notifiable disease

Mortality

Death from notifiable disease