What Are the 4 Types of Infections?

Medically Reviewed on 10/6/2021
what are the 4 types of infections
Infection occurs when germs enter your body and multiply, resulting in disease. The four main types of infections are viral, bacterial, fungal, and parasitic

Infection occurs when germs enter your body and multiply, resulting in disease. There are four main types of infections:

  1. Viral
  2. Bacterial
  3. Fungal
  4. Parasitic

In response to an infection, the immune system goes into overdrive, activating white blood cells and antibodies to fight the foreign invader. This can cause symptoms such as fever, headache, and rash.

1. Viral infection

Viruses can cause a wide range of infectious diseases. Viruses cause illness by killing cells or interfering with cell function.

The virus infiltrates a host's body and attaches itself to a cell, where it releases its genetic material. The virus multiplies as the cell replicates. When a cell dies, more viruses are released, infecting new cells. Some viruses alter the function of cells rather than killing them.

Bodies frequently respond by inducing fever (heat inactivates many viruses), secreting a chemical called interferon (which prevents viruses from reproducing) or mobilizing the immune system's antibodies and other cells to target the invader.

Most viral diseases are self-limiting, and the immune system may be able to fight them off. In rare cases, doctors may prescribe antiviral medications. Vaccinations can also help fight viral diseases.

2. Bacterial infection

Bacteria cause a wide range of infectious diseases, including strep throat and urinary tract infections, meningitis, and tuberculosis. Bacteria are also to blame for many skin rashes.

Bacteria can enter the body through wounds, scrapes, and surgical incisions, as well as the mouth and nose. Some bacteria proliferate so quickly that they crowd out host tissues and disrupt normal function. Some may kill cells and tissues right after they multiply. Sometimes, these produce toxins that can paralyze, destroy cells or trigger a massive immune response that is toxic.

Antibiotics are the first-line defense against bacterial infections.

3. Fungal infection

Fungal infections are often more bothersome than dangerous. However, some can cause serious illness.

Inhaling fungal spores is one of the most common ways for an internal fungal infection to develop. Fungal spores are frequently found in decaying vegetation or on animal feces. 

Fungal cells can invade the healthy tissues and disrupt their function. The body often launches an immune response against fungal particles, which causes collateral damage to the cells.

Infected people are treated with a combination of antibiotics and antifungal medications.

4. Parasitic infection

Protozoa are a type of parasite that thrive on moisture and frequently spread disease via water. Some protozoa cause intestinal infections, resulting in diarrhea, nausea, and stomach upset.

In healthy people, parasites cause mild illness, but those with severely weakened immune systems can develop serious infections that can spread to major organs.

Oral rehydration therapy is usually the first-line treatment. Antiparasitic drugs with a broad spectrum of action can be used to treat severe cases.

What are other types of infection?

  • Endogenous: Infection that develops within the body due to organisms already present in the body.
  • Exogenous: Infection that starts outside the body, caused by foods, fluids, fomites, etc.
  • Nosocomial: Hospital-acquired infection that is typically resistant to antibiotics
  • Opportunistic: Infection that occurs when the body's defenses are compromised (acquired immune deficiency syndrome, cancer, diabetes). 
    • Examples: Kaposi's sarcoma and Clostridioides difficile diarrhea

How can you prevent infections?

You can help prevent the spread of infection by following these tips:

  • Practice hand hygiene
  • Keep up-to-date with immunization 
  • Practice cough and sneeze etiquette
  • Clean surfaces regularly
  • Keep sick children at home as much as possible
  • Prepare food safely
  • Practice safe sex
  • Do not share personal belongings
  • Travel wisely and maintain social distancing
  • Use masks and sanitizers frequently


Bowel regularity means a bowel movement every day. See Answer
Medically Reviewed on 10/6/2021
What are the different types of infections? https://www.sepsis.org/news/viral-bacterial-fungal-what-are-the-different-types-of-infections/

Infections – bacterial and viral. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/infections-bacterial-and-viral

Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease, 5th ed. New York: Garland Science; 2001. Infectious agents and how they cause disease. https://www.ncbi.nlm.nih.gov/books/NBK27114/