What are the methods to control transmission of infectious diseases?

Germs are a part of everyday life and are found in our air, soil, water, and in and on our bodies. Some germs are helpful, others are harmful. Many germs live in and on our bodies without causing harm and some even help us to stay healthy. Only a small portion of germs are known to cause infection.

An infection occurs when germs enter the body, increase in number, and cause a reaction of the body.

Three things are necessary for an infection to occur:

Source: Places where infectious agents (germs) live (e.g., sinks, surfaces, human skin)
Susceptible Person with a way for germs to enter the body
Transmission: a way germs are moved to the susceptible person

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A Source is an infectious agent or germ and refers to a virus, bacteria, or other microbe.

In healthcare settings, germs are found in many places. People are one source of germs including:

Patients
Healthcare workers
Visitors and household members

People can be sick with symptoms of an infection or colonized with germs (not have symptoms of an infection but able to pass the germs to others).
Germs are also found in the healthcare environment. Examples of environmental sources of germs include:

Dry surfaces in patient care areas (e.g., bed rails, medical equipment, countertops, and tables)
Wet surfaces, moist environments, and biofilms (e.g., cooling towers, faucets and sinks, and equipment such as ventilators)
Indwelling medical devices (e.g., catheters and IV lines)
Dust or decaying debris (e.g., construction dust or wet materials from water leaks)

A susceptible person is someone who is not vaccinated or otherwise immune, or a person with a weakened immune system who has a way for the germs to enter the body. For an infection to occur, germs must enter a susceptible person’s body and invade tissues, multiply, and cause a reaction.

Devices like IV catheters and surgical incisions can provide an entryway, whereas a healthy immune system helps fight infection.

When patients are sick and receive medical treatment in healthcare facilities, the following factors can increase their susceptibility to infection.

Patients in healthcare who have underlying medical conditions such as diabetes, cancer, and organ transplantation are at increased risk for infection because often these illnesses decrease the immune system’s ability to fight infection.
Certain medications used to treat medical conditions, such as antibiotics, steroids, and certain cancer fighting medications increase the risk of some types of infections.
Lifesaving medical treatments and procedures used in healthcare such as urinary catheters, tubes, and surgery increase the risk of infection by providing additional ways that germs can enter the body.

Recognizing the factors that increase patients’ susceptibility to infection allows providers to recognize risks and perform basic infection prevention measures to prevent infection from occurring.

Transmission refers to the way germs are moved to the susceptible person.

Germs don’t move themselves. Germs depend on people, the environment, and/or medical equipment to move in healthcare settings.

There are a few general ways that germs travel in healthcare settings – through contact (i.e., touching), sprays and splashes, inhalation, and sharps injuries (i.e., when someone is accidentally stuck with a used needle or sharp instrument).

Contact moves germs by touch (example: MRSA or VRE). For example, healthcare provider hands become contaminated by touching germs present on medical equipment or high touch surfaces and then carry the germs on their hands and spread to a susceptible person when proper hand hygiene is not performed before touching the susceptible person.
Sprays and splashes occur when an infected person coughs or sneezes, creating droplets which carry germs short distances (within approximately 6 feet). These germs can land on a susceptible person’s eyes, nose, or mouth and can cause infection (example: pertussis or meningitis).
- Close range inhalation occurs when a droplet containing germs is small enough to breathe in but not durable over distance.
Inhalation occurs when germs are aerosolized in tiny particles that survive on air currents over great distances and time and reach a susceptible person. Airborne transmission can occur when infected patients cough, talk, or sneeze germs into the air (example: TB or measles), or when germs are aerosolized by medical equipment or by dust from a construction zone (example: Nontuberculous mycobacteria or aspergillus).
Sharps injuries can lead to infections (example: HIV, HBV, HCV) when bloodborne pathogens enter a person through a skin puncture by a used needle or sharp instrument.

Infection control practices are critical to reduce the transmission of infections from one person to another, such as from a healthcare worker to a patient or vice versa. See:

What is Infection Control?

In health care and public health practice settings, infection control includes various measures that prevent and contain the spread of infectious disease. These measures include:

Hand Washing
Infection control standard, contact, droplet and airborne precautions
Procedures for decontamination of persons and disinfection of equipment and the environment
Quarantine of contacts (if necessary)
Prophylaxis of exposed individuals
Control of the vectors of infection

Infection control is a health and safety issue. All people working in the health service organisation are responsible for providing a safe environment for consumers and the workforce. Infection prevention and control programs should be in place, in conjunction with use of the hierarchy of controls, to reduce transmission of infections so far as is reasonably practicable.

Infectious agents transmitted during provision of health care come primarily from human sources, including patients, members of the health workforce and visitors. Successful infection prevention and control measures involve implementing work practices that prevent the transmission of infectious agents using a two-tiered approach: standard precautions and transmission-based precautions.

Standard precautions are basic infection prevention and control strategies that apply to everyone, regardless of their perceived or confirmed infectious status. Strategies include hand hygiene, personal protective equipment, cleaning, and appropriate handling and disposal of sharps. These are a first-line approach to infection prevention and control in health service organisations and are routinely applied as an essential strategy for minimising the spread of infections. Standard precautions minimise the risk of transmission of infectious agents from one person or place to another, even in high-risk situations, and render and maintain objects and areas as free as possible from infectious agents.

Transmission-based precautions are specific interventions to interrupt the mode of transmission of infectious agents. They are used to control infection risk with patients who are suspected or confirmed to be infected with agents transmitted by contact, droplet or airborne routes. Transmission-based precautions are recommended as extra work practices in situations when standard precautions alone may be insufficient to prevent transmission. Transmission-based precautions are also used during outbreaks to help contain the outbreak and prevent further infection. Transmission-based precautions should be tailored to the infectious agent involved and its mode of transmission – this may involve a combination of practices.

Hand hygiene is an essential infection prevention and control strategy. The current National Hand Hygiene Initiative promotes a multimodal approach to improving hand hygiene. That includes:

The use alcohol-based hand rub at the point-of-care
Ensuring uniform hand hygiene and infection prevention and control education
Monitoring hand hygiene compliance and performance feedback
Using hand hygiene programs that ensure culture change.

Aseptic technique, use of invasive medical devices, workforce immunisation and screening for vaccine-preventable diseases, and environmental cleaning are also important elements of infection prevention and control systems. Health service organisation management is responsible for overseeing the systems and processes to maintain a clean, hygienic environment, including maintenance and upgrading of buildings and equipment; environmental cleaning of the buildings and infrastructure; evaluation of the infection risks for new products or equipment; and linen handling and management.

For further information on implementing systems for standard and transmission-based precautions, refer to the Australian Guidelines for the Prevention and Control of Infection in Healthcare.