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Last updated: 12.04.21

What are the Different Methods of Infection?

Now more than ever, staying healthy and preventing the spread of infectious diseases is at the forefront of many people’s minds. Whilst a lot of infections are not serious and can be easily treated, the best way to keep yourself and others safe is to avoid transmitting or spreading infection as much as possible.

Understanding the different methods of infection is a key part of being able to avoid getting infected yourself or infecting others around you. Here is our guide to the different methods of infection and some basic advice on how to prevent the spread of disease. 

Types of Infection


Bacterial infections are caused by bacteria, which are single cell microorganisms. Whilst a lot of bacteria do not cause any harm and live in a wide variety of environments, some of them can cause infection if they enter the body.

Common examples of types of bacterial infection include urinary tract infections, food poisoning caused by bacteria like salmonella, tuberculosis, Lyme disease and cholera.

Bacteria come in a wide range of shapes and sizes, and work by multiplying once inside the body and sometimes attacking cells or other ‘good’ bacteria to cause illness. They are usually treated using antibiotic medicine, but some strains of bacteria have evolved to become resistant to antibiotics.


Viral infections are caused by virus organisms, which are much smaller than bacteria and consist of a strand of genetic information surrounded by a shell of protein. They are parasitic in nature and require a host cell in order to survive, reproduce and carry out their function.

Common examples of infections caused by viruses include the common cold, chicken pox, HIV, rabies and coronavirus.

Viruses are much harder to treat than bacterial infections, and in many cases recovery relies on managing symptoms until your immune system has got rid of the infection. There are some antiviral drugs available for certain infections, but in some cases a virus might stay in your body for the rest of your life and lie dormant until something activates it again.


Fungal infections are caused by fungus, which is a type of small organism that includes substances like mould. They can be as small as bacteria, but some funguses are visible to the naked eye.

Many types of fungus are harmless to humans, but some can cause common infections like athlete's foot, ringworm or thrush.

Fungi tends to spread by releasing spores, and infection often develops in the upper layer of the skin or inside the body if the spores are inhaled. Fungal infections on the skin can be treated with antifungal cream, and more serious infections are often treated with oral antifungal medication or intravenous medication.


Prion infections are the rarest types of infection, but one of the most deadly. A prion isn’t actually an organism but a protein which can affect other proteins in the body and cause them to change into an abnormal shape.

Examples of diseases caused by a prion infection include dementia, Creutzfeldt-Jakob disease and bovine spongiform encephalopathy. Conditions involving prions are often inherited, but they can be picked up from consuming contaminated food or drink.

There is currently no cure for prion infection, although certain drugs can be used to slow the progress of infection and the spread of disease.

Methods of Infection

There are quite a few different methods of infection, but the most common of these can be divided into two different categories.

Direct Contact

Direct transmission of infection comes from direct contact between an infected person or animal and another, healthy person or animal. Common types of direct contact include:

  • Person to Person

Many infectious diseases are transmitted through person to person contact. This can happen through a variety of different actions between people, such as exchanging bodily fluids or touching hands and other body parts.

Pregnant women can also transmit infection to their unborn babies in this way through the placenta, with some types of STD able to pass from mother to child during childbirth.

  • Droplet

A very common method of infection transmission is through droplets which are produced when an infected person coughs or sneezes. In some cases, droplets containing infectious agents can also be produced when someone is just speaking. 

This method of infection requires close proximity to another person in order to spread.

Indirect Contact

Indirect transmission of infection also occurs when one person passes an infection to another, but the two people do not have to be in direct contact for this to happen. In this way, infections are spread through the air or via other mechanisms.


This method of transmission works similarly to droplet transmission, but involves infectious agents that can stay in the air for a long time. This can happen when someone coughs, sneezes or just breathes.

If you inhale an airborne infectious agent then you are very likely to become infected as well. In serious cases, entering a room after someone infectious has been breathing in there previously can result in airborne infection transmission.

Contaminated Objects

A contaminated inanimate object is also known as a fomite, which acts as a vehicle to pass an infectious disease from an infected person or animal to a healthy one. Whilst some infectious organisms can only survive whilst they are inside a living being, some can survive for a short time on a surface and therefore can be transmitted through indirect contact. Common fomites include door handles, worksurfaces and shared electronic devices like tablets or keyboards.

Infection transmission occurs when an infected person touches their mouth, nose or eyes and then does not wash their hands before touching a surface or an inanimate object. Another person then only has to touch that surface or object and then touch their own eyes, mouth or nose to potentially become infected. 

Food and Drink

Contaminated food and drink is a key way in which infectious diseases like E. coli or cholera are transmitted from a substance to a person. If you ingest any food or drink that contains an infectious agent, you are likely to become infected yourself.

Incorrectly cooked or stored food can also be a breeding ground for harmful organisms that can cause infection, which is why good food hygiene is such an important method of preventing infection.


A significant way in which bacterial infections are transmitted is fecal-oral contact, where microscopic amounts of faeces that contain harmful organisms are picked up from animals or humans and then accidentally ingested. The most common way that this type of indirect contact occurs is through people incorrectly washing their hands before preparing and then serving or eating food, which is why good hand hygiene is another incredibly important part of preventing the transmission of infection. 

Insect Bites

Infection transmission through an insect bite is also known as vector transmission, and occurs when an insect that is carrying an infectious agent bites a human or an animal. It is particularly common in insects that consume blood like mosquitoes, ticks, fleas and occasionally even spiders.

The insect carrying the infection may not actually have the disease themselves, and instead just carries it from one living organism to another. Once an infected insect has bitten another living creature the infection moves into their blood and can immediately cause disease or lay dormant for a while before symptoms start to show. 

How to Prevent the Spread of Infection

Whilst it can be incredibly easy to transmit infection without even realising, there are many simple steps to preventing the spread of infection that can help you and the others around you. These methods include:

  • Good hand hygiene: Washing yours hands after you have been to the toilet, before you prepare food, before you eat any food and before you do any activity that will involve putting your hands near your mouth, eyes and nose is incredibly important to stopping the spread of infection. 
  • Good respiratory hygiene: Covering your mouth and nose when you cough or sneeze is the best way to prevent the spread of infection when you have a cold or the flu. Either cough or sneeze into a tissue or your elbow and then make sure you wash your hands as soon as possible before touching anything else.
  • Being careful with food: Washing your hands before cooking or eating is very important, but so is ensuring that the area you are preparing and eating food in is also clean and that you are washing dishes and kitchen utensils properly. It is also vital that you make sure that food is cooked thoroughly before eating, that all food is stored in the correct conditions, and that you do not consume any food or drink that has gone off and as you may end up with food poisoning
  • Stay home when unwell: The best ways to avoid spreading infections is to stay at home if you know you have an infectious disease such as a cold, the flu or a stomach bug. If you are not coming into contact with other people or contaminating surfaces or areas that other people use, you won’t pass on the infection.
  • Vaccination: A lot of infections can now be prevented by vaccinations. Many vaccinations for serious infectious diseases are now mandatory when you are a child or young adult, but other vaccinations are also available for people travelling to new countries where disease might be more prevalent.
  • Safe sex: Many infectious diseases can be spread through shared bodily fluids, including almost every sexually transmitted disease. To avoid catching an unwanted STD or infecting any sexual parters, practicing safe sex is essential.
  • Use insect repellent: To avoid catching and then spreading any infections that are transmitted through insect bites, you can use insect repellent or sprays to avoid getting bitten in the first place.
  • Don’t share: Sharing food and drink with another person is an easy way to unintentionally transmit infection, as is sharing other personal items like toothbrushes, flannels or even glasses.
  • Cover your cuts: If you manage to cut or scrape your skin you are more at risk of picking up an infection through this wound, so it is important to keep injuries like this covered to avoid infection and further complications. You should also avoid touching any scrape or cuts unless you have thoroughly washed your hands.
  • Avoid wild animals: Some wild animals can carry infectious agents that cause serious diseases in humans, so it is safer to avoid contact with wild animals all together to prevent bites or scratches. If you do get scratched or bitten by an animal you should always see a doctor as soon as possible. 
  • Travel safely: If you are visiting a country or part of the world where there are higher rates of infectious diseases, the best way to avoid contracting or spreading infection is to avoid these places all together. Vaccinations are available for many common infections, but you lower your chances even further if you stay away from infectious zones.


What is an infection?

An infection is a type of illness that occurs when a harmful organism that is not normally present enters your body and causes disease. The severity of an infection and the symptoms that it causes are incredibly varied depending on what kind of organism it is caused by and how quickly it spreads and gets treated.

What are the main ways an infection can get into the body?

The main routes that infection enters the body are through the air, through touch, through bodily fluids, through ingestion or through bites from other living creatures.

What are the methods of infection control?

There are many different methods of controlling infection, but some of the most basic include practising good hand hygiene, practising good respiratory hygiene (or cough etiquette), using personal protective equipment, carefully disposing of waste and ensuring that surfaces and items are thoroughly disinfected. Handling needles and their sharp objects safety is also another key part of controlling infection, particularly in relation to injections.


Whilst it can be worrying to read about how easily infection can be transmitted and spread, it is worth knowing that the vast majority of infectious agents are not particularly harmful and are incredibly simple to prevent. By being aware of the ways in which infectious diseases can be spread, you can be better prepared to avoid any risks of contamination and transmission.

If you’d like to learn more about methods of infection and the ways in which you can prevent the spread of disease, Virtual College has a ‘Reducing the Spread of Infection’ online course available, as well as a free ‘Introduction to Infection and Prevention’ resource.