146. CCA Study Notes: Infection Spread, Transmission, Prevention, and Communicable Illnesses

The Big Picture

Infection prevention starts with understanding how harmful microbes move from one place or person to another. Exposure does not always lead to illness. The body sometimes destroys the harmful microbe, while some people carry it without becoming ill.

For infection to spread, several connected parts must be present. Breaking one part of this chain helps reduce the spread of infection. Support workers also need to recognize possible signs of infection, especially in older clients whose symptoms sometimes look different.

Look for Nova Scotia CCA Notes throughout this page for current provincial guidance.

Jump to:

Course Notes: Key Ideas You Need to Know

What Is an Infection?

An infection is a disease state that develops when disease-causing microbes invade and grow in the body.

A pathogen is a microbe capable of causing disease.

Pathogens enter the body from different sources. A contaminated object, such as soiled linen, is one possible source. Another person with a communicable disease is another source.

A communicable disease, also called a contagious disease, is caused by microbes that spread easily. Examples include the common cold, influenza, chicken pox, hepatitis, pneumonia, and tuberculosis.

Local and Systemic Infections

A local infection affects one part of the body. An infected cut on an arm is one example.

A systemic infection involves the whole body. The person has generalized signs and symptoms rather than symptoms limited to one area.

Three Possible Outcomes After Exposure to a Pathogen

Exposure to a pathogen does not always result in infection.

1. The immune system destroys the pathogen. The pathogen does not survive and grow, so infection does not develop. Previous exposure to the same pathogen sometimes gives the body immunological memory that helps it fight the pathogen without symptoms.
2. The pathogen remains, but infection does not develop. A person might remain healthy while still carrying the pathogen. These people are called carriers. A carrier is able to transfer the pathogen to other people without developing an active infection.
3. An infection develops after exposure. The time between exposure and the beginning of illness is the incubation period. It ranges from hours or days to years, depending on the pathogen. A person is able to spread the pathogen during this period.

The communicable phase is the period when a person is infectious and able to spread pathogens to others. Its length varies between pathogens.

Health Care-Associated Infections

A health care-associated infection (HAI) is acquired after admission to a health care facility or while receiving care from a health care provider.

The older term nosocomial infection refers to what is now called an HAI.

Infections also occur in home care and other community settings. Workers transfer microbes between clients or from themselves to clients. Health care workers may recover from infections and develop memory cells that make symptoms less likely. They may still carry pathogens to unhealthy clients or other vulnerable people. Equipment used for treatments, therapies, and tests also provides a route for microbes if it is not kept free of pathogens.

Common infections in health care settings include:

• Respiratory tract infections, including colds, pneumonia, bronchitis, and influenza
• Urinary tract infections
• Gastrointestinal tract infections that cause nausea or diarrhea
• Skin infections, including wound and intravenous site infections

Sick, frail, and older clients often have greater difficulty fighting infection.

Three practices help prevent infection in health care settings:

1. Medical asepsis, especially hand hygiene
2. Isolation precautions
3. Surgical asepsis

The Chain of Infection

The chain of infection describes the connected factors involved when infection spreads.

There are six links.

1. Pathogen

A pathogen is a microbe capable of causing disease.

2. Reservoir

A reservoir is the environment where a pathogen lives before infecting another person.

Reservoirs include:

• People
• Animals
• Food
• Water
• Soil
• Inanimate objects

A person or animal that carries a pathogen is a host.

3. Portal of Exit

The portal of exit is the route the pathogen uses to leave its reservoir.

Human portals of exit include:

• Mouth
• Nose
• Rectal opening
• Vaginal opening
• Urethral opening
• Breaks in the skin, including cuts, scrapes, or wounds
• Breaks in mucous membranes

Pathogens also leave through blood, body fluids, excretions, and secretions. Examples include urine, stool, vomit, saliva, mucus, pus, vaginal discharge, semen, wound drainage, and sputum ⓘ.

4. Mode of Transmission

The mode of transmission describes how the pathogen travels from its portal of exit toward another host or reservoir.

Transmission includes:

• Direct physical contact
• Indirect physical contact
• Droplets
• Air currents
• Vehicles
• Vectors
• Fomites

A fomite is a nonliving object that carries infectious organisms and serves as a route of transmission. Bed linen is one example.

Some microbes spread in more than one way.

5. Portal of Entry

The portal of entry is where the pathogen enters the new host.

Human portals of entry include body openings and breaks in the skin or mucous membranes.

6. Susceptible Host

A susceptible host is a person at risk for infection.

Risk depends partly on the person’s immune system and whether memory cells remain from previous exposure to the pathogen.

A person with a weakened immune system is immunocompromised and has a greater risk of infection.

Modes of Transmission

Contact Transmission

Contact transmission occurs when microbes spread through physical touch. It includes direct and indirect contact.

Direct contact: A person touches someone who is infected or colonized. Personal care activities such as bathing or turning a client involve skin-to-skin contact. Even shaking hands transfers microbes.

Indirect contact: A person touches a contaminated object. Examples include:

• Soiled linen
• Tissues
• Eating and drinking utensils
• Dressings
• Equipment
• Surfaces in a client’s room

Examples of infections associated with contact transmission include multidrug-resistant organisms, gastrointestinal organisms, skin infections, and wound infections.

Droplet Transmission

Droplet transmission occurs when tiny drops of liquid carry microbes through the air across short distances of less than 1 m.

Coughing, sneezing, and talking send these droplets into the air. The droplets then settle on another person or an object.

Examples include:

• Meningitis
• Pneumonia
• Influenza, including H1N1
• Mumps
• COVID-19

Airborne Transmission

Airborne transmission occurs when air currents carry microbes farther than 1 m.

The microbes travel in dust particles or evaporated droplets. They travel across a room or farther. A person inhales the microbes or comes into contact with microbes deposited on the skin.

Examples include:

• Measles
• Chicken pox
• Tuberculosis
• SARS
• Febrile respiratory illness
• COVID-19

Vehicle Transmission

Vehicle transmission occurs through a contaminated source.

Common vehicles include:

• Food
• Water
• Medication
• Invasive medical equipment
• Body fluids

One contaminated vehicle might spread microbes to many people and result in an outbreak.

Examples include hepatitis A, B, and C and HIV/AIDS.

Vectorborne Transmission

A vector is another organism that transfers pathogens from one host to another without causing the infection itself.

Vectors include:

• Fleas
• Ticks
• Mites
• Mosquitoes
• Mice

West Nile virus and Lyme disease are examples of illnesses spread this way. Vectorborne transmission is rare in health care settings.

Factors That Increase the Risk of Infection

Several factors increase a person’s infection risk:

• Extremes of age, especially the very young and very old
• Poor nutrition
• Stress
• Lack of sleep
• Diseases, illnesses, or treatments that weaken the immune system
• Certain medications
• Invasive procedures, including intubation and surgery
• Invasive devices, including intravenous lines and urinary catheters
• Open wounds
• Close contact with people who have communicable diseases
• Contact with multiple caregivers

Signs and Symptoms of Infection

Possible signs and symptoms include:

• Fever and chills
• Increased pulse and respiratory rates
• Aches, pain, or tenderness
• Fatigue and loss of energy
• Loss of appetite
• Nausea
• Vomiting
• Diarrhea
• Rash
• Sores on mucous membranes
• Redness and swelling of a body part
• Discharge or drainage from an infected area, sometimes with a foul odour
• New or increased cough, sore throat, or runny or stuffy nose
• Burning pain during urination, more frequent urination, or greater urgency
• Behavioural changes in older persons

Infection in Older Clients

Older people have a greater risk of infection because of normal age-related changes. Those who already have serious health concerns also face a greater risk of severe illness or death from infection.

Older people often do not show the usual signs of infection. Fever, pain, and swelling are often absent. Older adults tend to have lower body temperatures and decreased pain sensation, and their immune response is often reduced.

A behaviour change is sometimes the only sign of infection.

Report: Tell your supervisor if an older client develops:

• New or increased confusion or delirium
• Increased nasal discharge or a productive cough
• New or increased incontinence
• Loss of appetite
• Decreased ability to perform activities of daily living, or ADLs
• Increased falls
• Changes in mood or usual behaviour

How Support Workers Help Break the Chain of Infection

Support workers have several specific ways to reduce the spread of infection.

1. Take care of your health. Get enough rest, eat nutritious food, stay physically active, avoid smoking, and keep immunizations current.
2. Bathe regularly and keep your hair, teeth, and nails clean. Never wear artificial nails when providing care.
3. Wear a clean uniform each day. Always change out of your uniform and duty shoes before going home after a shift. Never wear them to a store.
4. Perform proper hand hygiene between contacts with clients.
5. Perform hand hygiene after removing used gloves and before putting on clean gloves.
6. Put gloves on immediately before a care task that requires them. Remove them immediately after the procedure. Perform hand hygiene immediately after removing them.
7. Never use hand sanitizer on gloved hands as a shortcut instead of changing gloves.
8. Avoid touching your face, hair, or clothing after performing hand hygiene.
9. Keep commonly touched surfaces clean and disinfected at home and at work. Examples include doorknobs, light switches, telephones, and keyboards.
10. Cough or sneeze into your arm instead of your hand. If you use a tissue, throw it away promptly and wash your hands immediately.
11. Keep immunizations up to date.
12. Avoid going to work if you have a fever.
13. Never place clean or soiled linens on the floor.
14. In a client’s home, follow the infection-prevention directions for home care.
15. Always use personal protective equipment, or PPE, properly.

Vaccinations and Infection Prevention

Vaccinations help prevent serious communicable illnesses in people vaccinated against those illnesses. A vaccine contains a live, weakened or killed bacterium or virus and is given by mouth or injection to produce active immunity ⓘ against a specific infectious disease.

Health care workers who receive recommended immunizations reduce infection risk for themselves and the clients they care for. Health care agencies require workers to have routine vaccinations up to date before starting work.

Hepatitis B

Hepatitis B vaccination consists of three injections over 6 months and is recommended for people working in health care settings.

Antibody levels can be checked periodically after vaccination to ensure immunity to hepatitis B.

Some facilities suggest hepatitis A vaccination, often along with hepatitis B vaccination, especially for workers who handle food.

Influenza

A yearly influenza vaccination is highly recommended and sometimes required for people working in health care.

Influenza is especially dangerous for older people and people with weakened immune systems.

Tuberculosis

Tuberculosis, or TB, is a highly infectious bacterial disease.

It is more common:

• Among people with immune problems
• In crowded living environments, including group homes, prisons, and long-term care facilities
• In developing countries with inadequate health care

New staff and residents in long-term care facilities are required to have a two-step TB skin test, or a chest X-ray when a physician considers it necessary.

Report: A support worker should inform their physician after suspected exposure to a client or family member who might have TB.

Pandemics

A pandemic occurs when a communicable illness or infection spreads quickly throughout a country or across the world.

Influenza is a highly contagious respiratory infection. Its symptoms include:

• Sore throat
• Cough
• Fever
• Muscular pain
• Weakness

People encounter different influenza strains during their lives. Previous exposure sometimes provides some protection because memory cells recognize some surface proteins.

A major change in influenza A sometimes creates a new strain that the immune system does not recognize. The information provided describes such major changes as occurring about three to four times in a century.

H1N1 Influenza

H1N1 emerged in North America in the spring of 2009. People had little or no natural immunity to the new virus, leading to serious and widespread illness.

H1N1 spreads in the same ways described for seasonal influenza. An infected person coughs or sneezes, and germs enter another person’s nose, eyes, or throat.

Germs also remain on hard surfaces such as counters and doorknobs. Hands pick them up, and the germs reach the respiratory system when a person touches the mouth, nose, or both.

H1N1 does not spread through eating pork or pork products or through blood transfusions.

The main symptoms are fever and cough.

A person who suspects H1N1 infection should see a health care provider.

More investigation was needed to confirm how long a person with H1N1 could spread the virus. The period was believed to begin 24 hours before symptoms started and continue for approximately 7 days after symptoms began.

COVID-19 Spread and Prevention

COVID-19 spreads mainly through infectious material such as respiratory droplets and through contaminated objects or surfaces.

Common symptoms listed include fever, cough, and shortness of breath. Other listed symptoms include:

• Fatigue
• Chills
• Body aches
• Headache
• Loss of taste or smell
• Sore throat
• Runny nose
• Nausea
• Vomiting
• Diarrhea

COVID-19 may progress to cause pneumonia, respiratory failure, and death. Care information for COVID-19 includes rest, fluids, and treatment of symptoms.

Older people, people with compromised immune systems, and people with comorbidities are among the vulnerable groups described.

Key measures listed for limiting spread include:

• Frequent hand hygiene
• Cleaning or disinfecting items and surfaces between client use using an agency-approved method
• Wearing face coverings or masks to reduce droplet spread
• Maintaining 2 m of physical distance in public places
• Avoiding crowds, especially indoors, according to local health-unit direction

Communicable Illnesses to Recognize

The following information helps you connect each illness with its route of spread, signs and symptoms, incubation period, care information, and immunization information. As you review each illness, look for the same four areas: how it spreads, signs and incubation period, care information, and immunization.

Chicken Pox and Shingles

Cause: Varicella zoster virus

Spread: Airborne

Signs and symptoms: Fever and painful fluid-filled sacs called vesicles. With shingles, the vesicles usually follow a nerve root in one area of the body.

Incubation period: 14 to 21 days

Care information: Rest and avoid scratching or irritating the vesicles. Shingles requires medical assessment for medication or treatment. The person should remain isolated from people who have not had chicken pox.

Immunization: Chicken pox immunization may be given as long as the person does not have symptoms.

Clostridium difficile

Clostridium difficile, or C. difficile, is bacterial.

Spread: Direct contact

Signs and symptoms: Severe diarrhea and abdominal cramping

Incubation period: 1 to 10 days

Care information: Rest, fluids, symptom management, and physician care are listed. Handwashing is especially important because hand rubs do not kill these bacteria. Isolation is required because C. difficile spreads easily.

Immunization: None listed.

Febrile Respiratory Illness

Febrile respiratory illness (FRI) is associated with influenza A.

Spread: Droplet-spread respiratory infections such as colds, influenza-like illness, and pneumonia

Signs and symptoms: Fever above 38°C (100.4°F) and new shortness of breath. Some older people and people with immune problems do not develop a high fever.

Incubation period: Within days after exposure

Care information: Rest, fluids, treatment of symptoms, doctor care, and airborne isolation precautions are listed.

Immunization: Influenza vaccine for certain viral strains.

Measles

Cause: Virus from the Paramyxovirus family

Spread: Airborne and direct droplet transmission

Signs and symptoms: Fever and rash. Symptoms are often mild and sometimes go unnoticed.

Incubation period: 6 to 19 days

Care information: Rest, isolation, and cool sponge baths.

Immunization: The vaccine is given with mumps and rubella vaccine as MMR.

Rubella

Cause: Rubivirus

Spread: Droplet and airborne transmission

Signs and symptoms: Begins with signs of an upper respiratory infection and a fine, raised rash.

Incubation period: 14 to 23 days

Care information: Rest and isolation from people who have not received the vaccine.

Immunization: MMR vaccine. The information provided states that the vaccine must never be given to women who are pregnant or trying to become pregnant.

Hepatitis A, B, and C

Spread:

• Hepatitis A spreads through direct contact with fecal-contaminated food or water.
• Hepatitis B and C spread through direct contact with contaminated blood or body fluids.

Signs and symptoms: Jaundice, swollen liver, loss of appetite, and changes in urine or stool colour.

Incubation periods:

• Hepatitis A: 2 to 6 weeks
• Hepatitis B: 4 to 20 weeks
• Hepatitis C: 2 to 26 weeks

Care information: The person must consult a physician for medical treatment. With hepatitis B and C, avoid contact with blood or body fluids.

Immunization: Vaccines are available for hepatitis A and B. No vaccine is listed for hepatitis C.

HIV and AIDS

Human immunodeficiency virus (HIV) and acquired immune deficiency syndrome (AIDS) are associated with viral infection.

Spread: Direct contact with contaminated blood or body fluids

Signs and symptoms listed: Chills, fever, cough, tiredness, confusion, stiff neck, oral lesions, nausea, and vomiting

Incubation period listed: 3 to 8 weeks

Care information: The person must consult a physician for medical treatment. Avoid contact with blood or body fluids.

Immunization: No vaccine is listed.

Human Papilloma Virus

Human papilloma virus (HPV) has more than 100 types. The information provided states that 30 to 40 types are most commonly spread through sexual contact and might cause cervical cancer.

Signs: Visible warts sometimes occur on the hands, feet, or in oral, anal, and genital areas.

Incubation period: 1 month to 2 years

Care information: The person must consult a doctor for medical treatment. Avoid contact with infected areas, blood, or body fluids and avoid sexual contact.

Immunization: Two vaccines are listed as preventing infection from types 16 and 18, which are described as causing 70% of cervical cancer. Suitability should be discussed before vaccination.

Multidrug-Resistant Staphylococcus aureus

Multidrug-resistant Staphylococcus aureus (MRSA) is bacterial.

Spread: Direct contact with a person who has MRSA or direct contact with a contaminated object

Signs and symptoms: The same signs as other skin infections. MRSA is also associated with pneumonia and necrotizing fasciitis ⓘ.

Incubation period: 2 to 3 days

Care information: Avoid contact with infected people or items. Infection requires medical care.

Immunization: No vaccine is listed.

Vancomycin-Resistant Enterococcus

Vancomycin-resistant Enterococcus (VRE) is bacterial.

Spread: Direct contact with a person who has VRE or direct contact with a contaminated object

Signs and symptoms: The same signs as other skin or diarrheal infections.

Incubation period: 1 to 8 weeks

Care information: Avoid contact with infected people or items. Infection requires medical care.

Immunization: No vaccine is listed.

Common Mix-Ups

Wrong Idea	Better Idea
A local infection affects the whole body.	A local infection affects one body part. A systemic infection involves the whole body.
Exposure always causes infection.	Exposure has three possible outcomes, and infection is only one of them.
A carrier has to be sick.	A carrier transfers a pathogen without developing an active infection.
Incubation period and communicable phase mean the same thing.	Incubation is the time from exposure to signs and symptoms. Communicable phase is the period when the person is infectious.
Direct contact involves a contaminated object.	Direct contact involves touching an infected or colonized person. Indirect contact involves contaminated objects.
Droplet and airborne transmission cover the same distance.	Droplet transmission is described as less than 1 m. Airborne transmission is described as farther than 1 m.
Older clients always develop fever, pain, and swelling with infection.	Older clients often lack these usual signs and sometimes show behaviour changes instead.