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Germs are everywhere -- in the air, water, soil, and even on you. While many germs are harmless, some may trigger infections that can make you sick. When germs invade your body and multiply, this causes a reaction and an infection happens. An infection requires three things:

  • A source. This is where germs live, such as door handles, countertops, or your skin.
  • A susceptible person. This is someone vulnerable to germs, like those who are unvaccinated against a disease or immune to it, or people with a weakened immune system.
  • Transmission. This is how the susceptible person receives germs.

Germs spread in several ways. Two of these include direct contact (touch) and airborne (through the air). Here’s a closer look at each and how you can prevent them.

What Is a Direct Contact Illness?

A direct contact illness is one that spreads when an infected person has direct bodily contact with someone who’s not infected and passes on a germ. It’s the most common way infections pass between people. 

It’s also possible to spread contact illnesses through indirect contact with an infected person’s items or environment. For example, GI illnesses can spread from person to person on objects like doorknobs or toilet handles.

Examples of direct contact illnesses

Norovirus, scabies, head lice, ringworm, and impetigo are all examples of illnesses you can spread through direct contact.

Illnesses spread through contact with bodily fluids

Some conditions are spread by direct contact with the mucus membranes or bodily fluids from an infected person. These include:

  • Cytomegalovirus (CMV): saliva, semen, vaginal fluids, urine, mucus, tears 
  • Hepatitis B: blood, saliva, semen, vaginal fluids
  • Hepatitis C: blood
  • Human immunodeficiency virus (HIV): blood, semen, vaginal fluids, breast milk

Stopping the spread of direct contact illness

There are things you can do to stop a direct contact illness before it circulates to other people.

  • Wash your hands. Clean them frequently with soap and water. You can use an alcohol-based hand rub if there’s no soap and water around.
  • Keep your hands away from your face. Try not to touch your eyes, nose, or mouth to avoid the spread of germs.
  • Clean and disinfect. This includes surfaces and objects that could be contaminated with a disease-causing virus.
  • Do not inject drugs. If you do inject drugs, do not share injection equipment, including syringes and needles.
  • Avoid unprotected sex. Use external or internal condoms and dental dams correctly every time you have sex.
  • Don’t share personal items. Never borrow razors, makeup tools, or toothbrushes.  
  • Make sure shared cosmetic equipment is sterile. This includes tattoo needles, piercing equipment, and manicure or pedicure tools.
  • Stay up to date on all vaccines. The best way to protect yourself from infectious diseases is to get vaccinated and follow up on all boosters.

What Is an Airborne Illness?

An airborne infection is one that you spread through small particles you breathe out. And the other person doesn't always need to be close by to get it. 

Airborne vs. droplet transmission

While similar, airborne and droplet transmission have key differences, including the size of the infectious particles you spread and how they react in the environment. 

Airborne particles are tiny, can stay in the air for a long time, and travel longer distances. You can breathe them in even if you’re some distance away from the source of the infection. 

Droplets are larger and released when you cough, sneeze, talk, or even breathe hard. Then they come into contact with the mouth, nose, or eyes of someone nearby. Since they’re larger and heavier, droplets land on surfaces quickly and stay within about 3 feet of the infected person. Some diseases can show features of both droplet and airborne transmission.

Examples of airborne illnesses

Some of the common diseases that spread through the air include:

  • Common cold (rhinovirus)
  • COVID-19 (coronavirus)
  • Flu (influenza)
  • Whooping cough (pertussis)

Stopping the spread of airborne illnesses

You can take steps to avoid the spread of an airborne illness:

  • Keep your distance. Curb close contact when you’re sick or with others who are ill.
  • Cover your mouth and nose. When you sneeze or cough, cover it up with a tissue. Then throw the tissue away. 
  • Improve ventilation. This is how air moves into, out of, and within a space. Better ventilation prevents virus particles from building up in the air indoors. You can open windows, turn on exhaust fans, and turn your thermostat to “on” instead of “auto.” Remember to change your air filters often to boost air filtration.   
  • Stay up to date on all vaccines. Getting vaccinated and staying current on all boosters is the best way to prevent infectious disease.

Questions and Answers About Direct Contact and Airborne Illnesses

Here are some questions you may have about airborne and direct contact diseases:

Can a disease spread through both the air and direct contact?

Yes. Some illnesses, like the flu and measles, can spread through both the air and direct contact. When you are infected and cough, sneeze, or talk, you release some viruses into the air. People near you can then breathe it in. You can also spread them by touching germy surfaces or objects, then your mouth, nose, or eyes.

Can vaccines protect you against airborne and direct contact diseases?

Yes. Vaccines work by causing proteins to build up in your body (called antibodies), which protect you from certain illnesses.

Is a disease airborne if pollution causes it?

No. For the most part, airborne diseases do not include those triggered by air pollution, smog, or dust.

Show Sources

Photo Credit: iStock / Getty Images Plus / Getty Images

SOURCES:

UK Health Security Agency: “What infections are, how they are transmitted and those at higher risk of infection.”

New Hampshire Department of Health & Human Services: “Airborne and Direct Contact Diseases.”

Maine Center for Disease Control & Prevention Division of Disease Surveillance: “Airborne and Direct Contact Diseases.”

CDC: “How Infections Spread,” “Influenza (Flu),” “Measles (Rubeola),” “COVID-19: How to Protect Yourself and Others,” “Key Facts About Seasonal Flu Vaccine.” 

Ather B, Mirza TM, Edemekong PE. Airborne Precautions. StatPearls Publishing, 2023.

Cleveland Clinic: “Antibodies.”

World Health Organization: “Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations.”

HIVinfo.gov: “HIV and Opportunistic Infections, Coinfections, and Conditions.”

Government of South Australia Health: “Ways infectious diseases spread.”