Germs: Protection against bacteria, viruses and infections (2023)

Germs: Understand and protect against bacteria, viruses and infections

Learn how germs work and what you can do to protect yourself.

By Mayo Clinic staff

Germs live everywhere. You can find germs (microbes) in the air; on food, plants and animals; in the ground and in the water - and on almost every other surface, including your body.

Most germs will not harm you. Your immune system protects you from infectious agents. However, some germs are tough enemies as they constantly mutate to breach your immune system's defences. Knowing how germs work can increase your chances of avoiding infection.

Infectious agents: From bacteria to worms

Types of infectious agents

Types of infectious agents

Germs: Protection against bacteria, viruses and infections (1)

Types of infectious agents

Infectious agents come in many shapes and sizes. Bacteria and protozoa are microscopic unicellular organisms. Viruses are even smaller. Mushrooms grow like plants. Helminths resemble worms.

(Video) The Immune System

Infectious agents come in many shapes and sizes. Categories include:

  • bacteria
  • viruses
  • Mushrooms
  • Protozoa
  • Helminths


Bacteria are single-celled organisms that can only be seen with a microscope. They're so small that if you line up a thousand of them, they could fit over the end of an eraser.

Not all bacteria are harmful, and some bacteria that live in your body are helpful. For example, Lactobacillus acidophilus — a harmless bacterium that lives in your gut — helps you digest food, destroy some disease-causing organisms, and provide nutrients.

Many disease-causing bacteria produce toxins — powerful chemicals that damage cells and make you sick. Other bacteria can invade the tissue directly and damage it. Some infections caused by bacteria include:

  • sore throat
  • Tuberculosis
  • urinary tract infection


Viruses are much smaller than cells. In fact, viruses are basically just capsules that contain genetic material. In order to reproduce, viruses invade cells in your body and hijack the machinery that makes cells work. Host cells are often eventually destroyed during this process.

Viruses are responsible for causing many diseases, including:

(Video) Bacteria and Viruses for Kids | Learn about these two kinds of microorganisms

  • AIDS
  • a cold
  • Ebola
  • Genital herpes
  • Flu
  • measles
  • Chickenpox and Shingles
  • Coronavirus Disease 2019 (COVID-19)

Antibiotics designed for bacteria have no effect on viruses.


There are many types of mushrooms and people eat several of them. Mushrooms are fungi, as are the molds that form the blue or green veins in some cheeses. And yeast, another type of fungus, is a necessary ingredient in most breads.

Other fungi can cause disease. An example is Candida - a yeast that can cause infections. Candida can cause thrush — an infection of the mouth and throat — in infants and people who take antibiotics or have a weakened immune system. Fungi are also responsible for skin diseases like athlete's foot and ringworm.


Protozoa are single-celled organisms that behave like tiny animals - they hunt and gather other microbes for food. Many protozoa live in your intestinal tract and are harmless. Others cause diseases like:

  • Giardiasis
  • Malaria
  • toxoplasmosis

Protozoa often spend part of their life cycle outside of humans or other hosts, living in food, soil, water, or insects. Some protozoa enter your body through the food you eat or the water you drink. Others, like the malaria protozoa, enter your body through mosquito bites.


Helminths are among the larger parasites. The word "helminth" comes from the Greek word for worm. When these parasites—or their eggs—invade your body, they lodge in your intestinal tract, lungs, liver, skin, or brain, where they feed on your body's nutrients. Helminths include tapeworms and roundworms.

Understand infection vs disease

There is a difference between infection and disease. Infection, often the first step, occurs when bacteria, viruses, or other microbes that cause disease enter your body and begin to multiply. Disease occurs when the cells in your body become damaged - as a result of the infection - and signs and symptoms of disease appear.

In response to infection, your immune system jumps into action. An army of white blood cells, antibodies, and other mechanisms go to work to rid your body of whatever is causing the infection. For example, when you're fighting a cold, your body may react with fever, coughing, and sneezing.

Defense against germs and infections

What is the best way to stay disease free? prevent infections. You can prevent many infections and avoid spreading infections by using simple tactics like these:

  • Avoid close contact with sick people.
  • Cover coughs and sneezes.
  • Avoid touching your face.
  • Stay home if you are sick.
  • Clean and disinfect frequently touched surfaces.
  • Avoid contaminated food and water.

You can also prevent infection by:

(Video) Immunity against viruses

  • Wash your hands.Often overlooked, washing your hands is one of the easiest and most effective ways to protect yourself from germs and most infections. Wash your hands with soap and water for at least 20 seconds. Wash your hands before preparing or eating food, after coughing or sneezing, after changing diapers, and after using the toilet. If soap and water are not available, alcohol-based hand sanitizer gels with at least 60%; Alcohol can offer protection.
  • vaccinations.Vaccination is your best line of defense against certain diseases. The more researchers understand about the causes of disease, the more diseases vaccines can prevent. Many vaccinations are given in childhood. But adults still need vaccines to prevent some diseases like tetanus, and influenzaCOVID-19.
  • medication.Some medications offer short-term protection against certain germs. For example, taking an antiparasitic medication can prevent you from contracting malaria if you travel to or live in a high-risk area.

When to see a doctor

See a doctor if you think you have an infection and you have experienced:

  • An animal or human bite
  • difficulty breathing
  • A cough that lasts more than a week
  • periods of rapid heartbeat
  • A rash, especially if accompanied by a fever
  • swelling
  • Blurred vision or other vision problems
  • Persistent vomiting
  • An unusual or severe headache

Your doctor can run diagnostic tests to find out if you are infected, how severe the infection is, and how best to treat this infection.

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March 08, 2022

  1. Overview of bacteria. Merck Manual Professional version. Retrieved September 12, 2019.
  2. Levinson W et al. Bacteria compared to other microorganisms. In: Review of Medical Microbiology and Immunology: A Guide to Clinical Infectious Diseases. 15th ed. McGraw-Hill Education; 2018. Retrieved September 16, 2019.
  3. Tuberculosis. National Institute of Allergy and Infectious Diseases. Retrieved September 17, 2019.
  4. Kimberlin DW, et al. Red online book. 31st ed. American Academy of Pediatrics; 2018. Retrieved September 18, 2019.
  5. Goering RV, et al. Mims' Medical Microbiology and Immunology. 6th ed. Elsevier; 2019. Retrieved September 19, 2019.
  6. Non-pharmaceutical interventions (NPIs). At home: flu prevention. Centers for Disease Control and Prevention. Retrieved September 18, 2019.
  7. Food and Water Safety. Centers for Disease Control and Prevention. Retrieved September 19, 2019.
  8. Malaria. Centers for Disease Control and Prevention. Retrieved September 19, 2019.
  9. Frequently asked questions about vaccines. Centers for Disease Control and Prevention. Retrieved September 19, 2019.
  10. lactobacilli. IBM Micromedex. Retrieved September 19, 2019.
  11. preventive measures. Centers for Disease Control and Prevention. Retrieved November 22, 2021.
  12. How to protect yourself and others. Centers for Disease Control and Prevention. Retrieved November 22, 2021.

For more information, see

See also

  1. Antibiotics: Are You Abusing Them?
  2. Infection: bacterial or viral?
  3. vaccines for children
  4. COVID-19: How can I protect myself?
  5. CRE bacteria: what you should know
  6. Ebola transmission: Can Ebola spread through the air?
  7. Enterovirus D68: how can I protect my child?
  8. hand drying
  9. Hand washing tips
  10. infectious diseases
  11. Mayo Clinic Minute: What is the Asian longhorn tick?
  12. Mayo Clinic Minute: You're washing your hands all wrong
  13. Mayo Clinic Minute: How Dirty Are Common Surfaces?
  14. Monkeypox: what is it and how to prevent it
  15. Mayo Clinic Vaccination Guide
  16. adult vaccines
  17. vaccines for children
  18. What are superbugs?
  19. What are superbugs and how can I protect myself from infection?
  20. What is chikungunya fever and should I be concerned?
  21. What is the Asian buck tick and where is it found?
(Video) The Immune System Explained I – Bacteria Infection



What are 3 ways to prevent infection from bacterial diseases? ›

Wash your hands with soap and water throughout the day. Get recommended vaccinations to prevent infectious diseases such as measles and chickenpox. Practice safer sex to protect against sexually transmitted infections (STIs) Stay home when ill.

What protects us from germs and diseases? ›

The immune system's job: defend against disease-causing microorganisms. Its goal is to keep us healthy. The immune system is a vast and complex interconnected network of many different organs, cells and proteins that work together to protect the body from illness.

What are the 4 types of germs? ›

The term "germs" refers to the microscopic bacteria, viruses, fungi, and protozoa that can cause disease.

What are the 3 methods of infection control? ›

Hand hygiene. Use of personal protective equipment (e.g., gloves, masks, eyewear). Respiratory hygiene / cough etiquette.

What are some ways to prevent infections? ›

What you can do
  1. Immunise against infectious diseases.
  2. Wash and dry your hands regularly and well.
  3. Stay at home if you are sick.
  4. Cover coughs and sneezes.
  5. Clean surfaces regularly.
  6. Ventilate your home.
  7. Prepare food safely.
  8. Practise safe sex.
Apr 5, 2022

What kills viruses naturally? ›

Using Vitamins and Minerals to Fight Viruses and Support Immunity
  • Vitamin D: Vitamin D, commonly known for its role in bone health, also helps make proteins that kill viruses and bacteria, especially in the respiratory tract. ...
  • Vitamin C: ...
  • Zinc: ...
  • Polyphenols: ...
  • Potassium: ...
  • Probiotics: ...
  • Supplement Wisely.

What is the prevention of viruses? ›

In those situations, use as many prevention strategies as you can, such as practicing hand hygiene, consistently and correctly wearing a high-quality mask, improving ventilation, and keeping your distance, when possible, from the person who is sick or who tested positive.

What are 2 ways to control bacteria? ›

Sterilization and decontamination through heat is the most effective way to control microbial growth. There are ways to selectively inhibit the growth of only certain microorganisms, like the use of antibiotics.

What is the body's first layer of defense against germs? ›

The innate immune system is the body's first line of defense against germs entering the body. It responds in the same way to all germs and foreign substances, which is why it is sometimes referred to as the "nonspecific" immune system.

What is natural protection from germs called? ›

This protection is called immunity. Humans have three types of immunity — innate, adaptive, and passive: Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection. For example, the skin acts as a barrier to block germs from entering the body.

How does the body protect itself from infection? ›

When harmful microbes (tiny particles) enter and invade the body, the body produces white blood cells to fight the infection. The white blood cells identify the microbe, produce antibodies to fight it, and help other immune responses to occur. They also 'remember' the attack. This is how vaccinations work.

What are the 7 causes of infection? ›

Pathogens that cause infectious diseases are viruses, bacteria, fungi, parasites and, rarely, prions. You can get infectious diseases from other people, bug bites and contaminated food, water or soil.

What are the 4 most common bacteria? ›

The bacteria and viruses that cause the most illnesses, hospitalizations, or deaths in the United States are described below and include:
  • Campylobacter.
  • Clostridium perfringens.
  • E. coli.
  • Listeria.
  • Norovirus.
  • Salmonella.
Mar 22, 2021

What are 4 methods to prevent cross infection? ›

Preventing and controlling infections
  1. Hand hygiene.
  2. Respiratory and cough hygiene.
  3. Cleaning.
  4. Toileting and sanitation.
  5. Personal protective equipment.
  6. Safe management of the environment.
  7. Safe management of linen and soft furnishings.
  8. Safe management of blood and bodily fluids.
Feb 13, 2023

What is the most common method to prevent infection? ›

Proper hand washing is the most effective way to prevent the spread of infections in hospitals. If you are a patient, don't be afraid to remind friends, family and health care providers to wash their hands before getting close to you.

What is the most effective and simplest way to prevent infection? ›

Hand washing is one of the simplest, most effective ways to prevent the spread of many types of infection and illness, including foodborne illness.

What vitamin fights infections? ›

Vitamin C was found to be beneficial against various groups of infectious agents including bacteria, viruses, Candida albicans, and protozoa (Table 2).

What food kills viruses? ›

1) Oysters, beef, pork chop, black eyed peas, pumpkin seeds- all of these foods are high in the mineral Zinc which helps to keep viruses from attaching to cells and helps prevent them from replicating. Zinc levels in your body may take time to build up, so start eating or supplementing early.

Does sugar feed viruses? ›

Most infectious bacteria and viruses bind to sugars on the surface of our cells. Most of the viruses feed on sugar.

How is bacteria prevented? ›

Keep your germs to yourself:

Always wash your hands after sneezing, blowing your nose, or coughing, or after touching used tissues or handkerchiefs. Use warm water and soap to wash your hands. If you don't have soap and water, use alcohol-base hand gel or disposable wipes.

How is bacteria treated? ›

Antibiotics are used to treat or prevent some types of bacterial infection. They kill bacteria or prevent them from reproducing and spreading. Antibiotics aren't effective against viral infections.

What is your best Defence against virus infection? ›

Use an anti-malware app - Installing an anti-malware app and keeping it up to date can help defend your PC against viruses and other malware (malicious software). Microsoft Defender is free anti-malware software included with Windows, and it's kept updated automatically through Windows Update.

What are the 4 steps to fight bacteria? ›

Four Steps to Food Safety: Clean, Separate, Cook, Chill. Following four simple steps at home—Clean, Separate, Cook, and Chill—can help protect you and your loved ones from food poisoning.

What cell kills bacteria? ›

Neutrophils and macrophages are both phagocytic cells known for ingesting bacteria and producing antimicrobial peptides, reactive oxygen species and other enzymes to fight infection.

What kills bacteria in the immune system? ›

White blood cells: Serving as an army against harmful bacteria and viruses, white blood cells search for, attack and destroy germs to keep you healthy. White blood cells are a key part of your immune system.

What are the three main enemies the immune system defends against? ›

The human body has three primary lines of defense to fight against foreign invaders, including viruses, bacteria, and fungi. The immune system's three lines of defense include physical and chemical barriers, non-specific innate responses, and specific adaptive responses.

What are 4 types of immunity? ›

Types of immunity: Active natural: Body produces antibodies in response to exposure to a live pathogen. Active artificial: Body produces antibodies in response to a vaccine. Passive natural: Antibodies are passed from the mom to her baby through the placenta and breastmilk.

What are the 4 stages of immune response? ›

The adaptive immune response in B cells, Helper T cells and Cytotoxic T cells involved four phases: encounter, activation, attack, and memory.

What are the two types of immunity? ›

There are two types of immunity: active and passive.

Is there a natural defense for bacteria? ›

Innate immunity provides the first line of defense against invading bacteria. The skin and mucous membranes provide physical and chemical barriers to infection. The normal bacterial flora antagonize colonization of body surfaces by nonindigenous bacteria. The internal tissues invariably contain bactericidal substances.

What is the medical term for germ? ›

(jerm) A bacterium, virus, or other microorganism that can cause infection and disease.

What are the 3 major functions of the immune system? ›

The tasks of the immune system
  • to fight disease-causing germs (pathogens) like bacteria, viruses, parasites or fungi, and to remove them from the body,
  • to recognize and neutralize harmful substances from the environment, and.
  • to fight disease-causing changes in the body, such as cancer cells.
Apr 23, 2020

What is the most common infection in the body? ›

Most Common Infectious Diseases in the U.S.
  • Chlamydia. 1/15. This sexually transmitted disease affects men and women. ...
  • Influenza A and B. 2/15. Sudden fever and chills, muscle aches, headache, tiredness, sore throat, congestion. ...
  • Staph. 3/15. ...
  • E. Coli. ...
  • Herpes Simplex 1. 5/15. ...
  • Herpes Simplex 2. 6/15. ...
  • Shigellosis. 7/15. ...
  • Syphilis. 8/15.
Jan 29, 2022

What are the 3 main sources of infection? ›

There are three main ways germs can be spread. These are by infected droplets (from a person or animal) being spread in the air, by germs in body fluids such as saliva, faeces, blood or urine contaminating a surface (contact) or by tiny particles spread into the air (airborne).

Where do bacteria live in the human body? ›

Where are Bacteria in the Human Body? Bacteria live on the skin, inside the nose, in the throat, in the mouth, in the vagina, and in the gut. The majority of the bacteria found in the body live in the human gut. There are billions of bacteria living there (Figure 2).

What is the most common bacteria? ›

There are four types of bacteria that are extremely common within a household. Staphylococcus, Micrococcus, Pseudomonas, and Bacillus are the most common types. Micrococcus is spherical, and can be found in meat products, in water, and in your soil.

What is deadliest bacteria? ›

The most deadly bacterial disease contracted by human beings is mycobacterium tuberculosis, the world's leading infectious disease with more than 1,700,000 deaths per year. As much as 13% of cases are resistant to most antibiotics, and about 6% are resistant or unresponsive to essentially all treatment.

What temperature kills bacteria? ›

Bacteria multiply rapidly between 40 and 140 degrees. Bacteria will not multiply but may start to die between 140 and 165 degrees. Bacteria will die at temperatures above 212 degrees. 2.3: How to Take Food Temperatures Know how to get an accurate reading with your thermometer!

What is the protection against viruses? ›

While the best way is antivirus software, operating systems already come with programs like Windows Defender and Windows Security. There are also other, free programs like Avast and Kaspersky. They may seem simple, but they're highly effective at destroying Trojan horses, worms and spyware.

How can we protect good bacteria? ›

How can you get healthy gut bacteria?
  1. Eat plenty of fiber-rich foods. When you think about your diet, consider the number of plant-based foods, grains, legumes and beans you're eating. ...
  2. Limit your sugar intake. ...
  3. Add fermented foods. ...
  4. Stay hydrated. ...
  5. Lower stress levels. ...
  6. Get enough sleep.
Apr 14, 2022

How does the body fight infection? ›

Antibodies. Antibodies help the body to fight microbes or the toxins (poisons) they produce. They do this by recognising substances called antigens on the surface of the microbe, or in the chemicals they produce, which mark the microbe or toxin as being foreign. The antibodies then mark these antigens for destruction.

What kills bacteria inside the body? ›

Antibiotics are medicines that help stop infections caused by bacteria. They do this by killing the bacteria or by keeping them from copying themselves or reproducing. The word antibiotic means “against life.” Any drug that kills germs in your body is technically an antibiotic.

How do bacteria protect humans? ›

The bacteria in our bodies help degrade the food we eat, help make nutrients available to us and neutralize toxins, to name a few examples[7]; [8]. Also, they play an essential role in the defense against infections by protecting colonized surfaces from invading pathogens[8]; [9].

What are the 3 ways the body protects itself from disease? ›

These specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity. Humans have three types of immunity — innate, adaptive, and passive: Innate immunity: Everyone is born with innate (or natural) immunity, a type of general protection.

What are the different types of prevention? ›

These preventive stages are primordial prevention, primary prevention, secondary prevention, and tertiary prevention.


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