NRSG 205 Chapter 14 Part 2 - Disease and Epidemiology (THREE)

Local infection

affects a small area of the body

Systemic infection

infection spreads throughout the body through the circulatory system

Primary infection

is acute and causes initial illness

Secondary infection

a second infection that occurs in a weakened host due to primary infection

Subclinical infection

inapparent infection where the host does not have signs or symptoms

Difference between STI and STD

1. STI: acknowledges that the pathogen is there, but the host may be asymptomatic

2. STD: the host shows the disease state and is symptomatic

4 considerations in infectious disease

1. Reservoir

2. Transmission

3. Invasion

4. Pathogenesis

Reservoir of infection

source of infection that can be human, animal, insects, and non-living things

3 types of transmission

1. Direct

2. Indirect

3. Through an arthropod

Invasion

allowing the pathogen to multiply

Pathogenesis

injury to the host

Human reservoir

carrier or person infected with the disease (i.e. STIs, typhoid)

Animal reservoir

animal that carries the pathogen

3 examples of animal reservoirs

1. Rabies

2. Plague

3. Lyme disease

Zoonoses

disease that affects a wild or domestic animal, which can then be transmitted to a human

Nonliving reservoirs

often soil (i.e. clostridium tetani) , water (i.e. cholera), and uncooked food

Direct transmission

close contact between the reservoir and the host

3 types of direct transmission

1. Congenital transmission

2. Fomite transmission

3. Droplet transmission

Congenital transmission

 mother → fetus/newborn

Fomite transmission

involves inanimate objects (indirect contact)

Droplet transmission

 saliva or mucous in coughing or sneezing - droplet nuclei (only travel a short distance, less than 1 m,  before falling to the ground)

Vehicle transmission

transmission by a medium such as air, water, or food

2 types of vehicle transmission

1. Airborne transmission

2. Foodborne transmission

Airborne transmission

droplets or dust travels a distance greater than 1 m

Foodborne transmission

can occur through cross-contamination of surfaces or fecal-oral transmission

Arthropod transmission

insects that act as vectors

2 types of arthropod transmission

1. Mechanical transmission

2. Biological transmission

Mechanical transmission

transmission is passive - the arthropod acts like a living fomite

Example of mechanical transmission

Flies landing on feces and then landing on food

Biological transmission

active transmission by the arthropod

Example of biological transmission

Malaria

Predisposing factors

factors that make the body more susceptible to disease or alter the course of the disease

7 predisposing factors

1. Gender

2. Climate

3. Aging

4. Fatigue

5. Inadequate nutrition

6. Genetics

7. Primary infection

5 steps of the development of disease

1. Incubation period

2. Prodromal period

3. Period of illness

4. Period of decline

5. Period of convalescenece

During which phase of the development of disease is the host most vulnerable to secondary disease?

Period of decline

Incubation period

time period between the initial infection and first appearance of signs and symptoms

What has occurred in relation to the pathogen during the incubation period?

1. Pathogen has entered the body

2. Host has not recognized the pathogen in the body

2 factors that the incubation period depends on

1. Microbe invading

2. Host’s resistance to that microbe

Prodromal period

characterized by the first mild signs and symptoms that are often generalized, like a fever, aches, etc. (not specific to the disease)

Length of the prodromal period

Relatively short period

Period of illness

the disease is at its height, and all signs and symptoms appear

Period of decline

signs and symptoms begin to subside

Period of convalescence

body returns to the pre-disease state and health is restored

Healthcare-association infections

infections acquired in healthcare settings

Another name for healthcare-associated infections

Nosocomial infections

2 types of microbes common in hospitals

1. Normal microbiota

2. Antibiotic resistant microbes

What is the most common cause of health-care associated infections?

Normal microbiota

Normal microbiota’s role in healthcare-association infection

introduced to other parts of the body through surgery or catheterization → opportunistic infection

3 ways that a host can become immunocompromised to healthcare-associated infections

1. Burns

2. Surgical wounds

3. Disease

What is the main way to control healthcare-associated infections? What are 2 subdivisions of this method?

Aseptic technique - standard precautions and transmission-baed precautions

Standard precautions

Always used in a medical or laboratory setting - gloves, lab coat, eyewear, etc.

Transmission-based precautions

specific procedures for a certain pathogen (such as wearing a mask when interacting with a patient with COVID-19)

What causes tetanus?

Clostridium tetani

Clostridium tetani reservoir

soil, dust and animal feces

Clostridium tetani transmission

occurs when bacterial spores enter the body through a deep wound, puncture or cut, especially in areas contaminated with dirt or feces

How does Clostridium tetani act in the body?

 Clostridium tetani produces a powerful toxin that affects the nervous system

Clostridium tetani incubation period

usually 3-21 days, but can vary depending on the type and location of the wound

5 signs and symptoms of Clostridium tetani

1. Muscle stiffness, especially in the neck and jaw

2. Dysphagia

3. Painful muscle spasms

4. Fever and sweating

5. Tachycardia

2 ways to prevent tetanus

1. DTap or Tdap vaccine

2. Proper wound care