Immune System and Infectious Diseases Overview

The purpose of the immune system is to keep infectious microorganisms, such as certain bacteria, viruses, and fungi, out of the body, and to destroy any infectious microorganisms that do invade the body. The immune system is made up of a complex and vital network of cells and organs that protect the body from infection.

When the immune system does not function properly, it leaves the body susceptible to an array of diseases. Allergies and hypersensitivity to certain substances are considered immune system disorders. In addition, the immune system plays a role in the rejection process of transplanted organs or tissue.

What are disorders of the immune system? 

When the immune system does not function properly, a number of diseases can occur. Allergies and hypersensitivity to certain substances are considered immune system disorders. In addition, the immune system plays a role in the rejection process of transplanted organs or tissue. Other examples of immune disorders include: 

• Autoimmune diseases such as juvenile diabetes, rheumatoid arthritis and anemia  
• Immunodeficiency diseases such as acquired immune deficiency syndrome (AIDS) and severe combined immunodeficiency (SCID)

What is an infectious disease? 

According to the Centers for Disease Control and Prevention (CDC), an infectious disease is caused by one or more of the following: 

• Viruses
• Bacteria  
• Parasites 
• Fungi  

Infectious diseases can range from common illnesses such as the cold, to deadly illnesses such as AIDS. Depending on the disease causing organism, an infection can spread in some or all of the following ways: 

• Sexual transmission - transmission of an infection through sexual contact, including intercourse.  
• Airborne transmission - transmission of an infection through inhaling airborne droplets of the disease, which may exist in the air as a result of a cough or sneeze from an infected person. 
• Blood-borne transmission - transmission of an infection through contact with infected blood, such as when sharing hypodermic needles. 
• Direct skin contact - transmission of an infection through contact with the skin of an infected person. 
• Insect-borne transmission - transmission of an infection through insects such as mosquitoes that draw blood from an infected person and then bite a healthy person. 
• Food-borne transmission - transmission of an infection through consuming contaminated food. 
• Water-borne transmission - transmission of an infection through contact with contaminated water. 

How do antibiotics work against infections? 

Antibiotics can be used to treat bacterial infections. However, antibiotics are ineffective in treating virus-related illnesses. In addition, antibiotics treat specific bacteria. Overuse or misuse of antibiotics can lead to drug-resistant bacteria. It is important that antibiotics are taken properly and for the duration of the prescription. If antibiotics are stopped early, the bacteria may develop a resistance to the antibiotics and the infection may occur.