What Is Infection?

An infection occurs when a foreign organism enters the body or multiplies in a harmful way. Bacteria, viruses, fungi, and parasites can all lead to infection. Also called germs, these organisms can multiply quickly and make you sick. Infections are very common. Often they can be treated at home, but in some cases they can be life threatening.

Organisms that cause infections often live on or near the body. But they don’t cause harm until something changes. For example, bacteria can live harmlessly on your skin but not cause infection until they enter your body through a cut.

Infections affect people in different ways. One person’s immune system might fight off an infection while another person’s can’t. Children have an increased risk of infection because they don’t have fully developed immune systems.

Some infections come from direct person-to-person contact, including sexual contact. A person can get an infection by touching contaminated objects, by eating contaminated food, or by breathing in bacteria, viruses, or fungi. Insect bites may also cause infection.

According to the World Health Organization, some common infectious diseases are:

  • influenza strains
  • cholera
  • dengue fever
  • hepatitis A, B, and E
  • Hansen’s disease (leprosy)
  • malaria
  • measles
  • meningitis
  • smallpox
  • tuberculosis
  • yellow fever

Other common and less serious infectious diseases are:

  • food poisoning
  • salmonella
  • tapeworm
  • common cold
  • chickenpox
  • cold sores
  • ear infections
  • pinkeye
  • urinary tract infections
  • sexually transmitted diseases
  • meningitis
  • mononucleosis
  • sinusitis
  • strep throat
  • tetanus
  • yeast infections
  • whooping cough
  • diaper rash
  • jock itch
  • athlete’s foot
  • pneumonia
  • warts

Infection occurs when infection-causing organisms enter the body, attack tissues, and release toxins. Organisms can enter through wounds on the skin, for example. Infection can also result from healthcare procedures. A catheter may cause a urinary tract infection, and infection can occur at the site of surgery incisions.

Bacterial infections occur when harmful bacteria enter the body. Some bacteria infections, such as staph infections, can be deadly if the bacteria enter the bloodstream, joints, or organs. Common bacterial infections include:

  • strep (strep throat, impetigo, UTIs, and pneumonia)
  • staph (blood infections and toxic shock syndrome)
  • E. coli.

Viral infections occur when viruses invade healthy cells in the body and multiply. Viral infections can be relatively harmless, but they can also be deadly. Examples are:

  • cold
  • flu
  • warts
  • smallpox

Fungal infections occur when a fungus, such as mold, enters or lands on the body. Fungal infections spread through the movement of spores. A fungus may land on the skin or nails or be inhaled into the lungs. Some fungal infections are:

  • athlete’s foot
  • yeast infections
  • nail fungus
  • fungal sinusitis
  • blastomycosis

Parasitic infections occur when parasites feed off of the body. Parasites may be transmitted by contaminated food or water, by animal or bug bites, or through direct contact with an infected person. Parasitic infections include:

  • malaria
  • giardia
  • tapeworms

Symptoms of infection will depend on the type of infection and where it is.

Symptoms of bacterial infections are often present around a wound or break of the skin, in the ear, or in the throat. These symptoms include:

  • inflammation
  • redness
  • swelling
  • warmth and localized pain
  • blisters and pus

Symptoms of other types of infection may include:

  • fever
  • chills
  • fatigue
  • loss of appetite
  • body aches
  • diarrhea
  • rashes
  • stiffness
  • pus drainage
  • limited range of motion
  • runny nose

Some mild infections can be managed at home, but others may be serious. If you suspect a serious infection, see your doctor right away. Without immediate treatment, infection can spread, leading to potentially serious health conditions.

To diagnose an infection, your doctor will do a physical examination. He or she will ask you about any injuries or events that possibly led to an infection. Your doctor might take blood or other fluid samples for testing. If your doctor suspects infection in the blood or bones, an X-ray or an MRI may be performed. These tests may help to identify the type or cause of the infection and the extent of tissue damage. This information will determine your treatment plan.

Treatment depends on the type of infection.

Bacterial infections are often treated with antibiotics, taken either intravenously or orally.

Viral infections are resistant to antibiotics. Some viral infections can be treated with antiviral medication.

Fungal infections may be difficult to treat. Anti-fungal medicines can be topical (applied to skin) or oral.

Parasitic infections are treated based on the underlying parasite. Medication may treat parasitic infections, but some infections are more easily treated than others.

Infections affecting the skin or soft tissues of the body might be treated by soaking in warm water. Other treatment options include antibiotics and/or ointments applied directly to the infected spot.

In some cases, your doctor will drain infection-related fluid or remove dead tissues. Very rarely, infection could lead gangrene and amputation.

Many infections respond well to antibiotics and heal without further complications. Overuse of antibiotics can lead to resistance, making infections harder to treat. Seeking treatment early will help reduce the risk of infection-related complications.

Not seeking treatment for infections can lead to further health problems. Many types of infection can spread to the blood, joints or other areas of the body, making them harder to treat. If infection spreads in this way, serious health complications may occur.

The easiest way to prevent infections is to practice good hygiene, especially with wounds or cuts. These tips will help prevent infection:

  • Wash your hands before touching wounds.
  • Be sure to keep wounds clean at all times, especially removing dirt, hair, and other debris.
  • Use sterile dressings and ointments.
  • Seek medical attention for deep wounds or wounds with a lot of foreign debris.

Others ways to reduce risk of infection:

  • Don’t share personal items such as razors.
  • Use caution if using tampons.
  • Get available vaccines (such as chickenpox, measles, and hepatitis).
  • Use safe sex techniques.
  • Consider additional vaccinations and be cautious about food consumption when traveling to developing countries.