Infectious Diseases

Reviewed By: Dr. Kurt Kloss, MD
Last Reviewed Date: Dec 13, 2021
Last Modified Date: Dec 13, 2021
Published Date: Oct 17, 2017

What is an infectious disease?

An infectious disease is an illness that occurs when your body is invaded by a pathogen, such as a virus or bacteria. These pathogens may be present in food or water, in the environment, in the air we breathe or in bodily fluids of infected individuals, waiting to invade our bodies and cause sickness. Many infectious diseases have similar symptoms and effects, while others may produce few or no signs or symptoms. So how do you know if you have caught one of these diseases? Infectious disease testing can give you the answers you need, determining whether you have contracted an infectious disease, as well as the specific type of pathogens that have invaded your body.

Aren't all diseases infectious?

Infectious diseases are caused by organisms that invade the body. While they are a very common type of disease, they are not the only type. Many diseases develop without any type of infection or pathogen present. For instance, osteoarthritis is a disease caused by wear and tear on the joints, and osteoporosis is caused by factors that include aging, low intake of bone-healthy nutrients, hormonal imbalances and insufficient exercise. Autoimmune diseases are caused by the body's own immune system attacking its cells, organs and tissues, and cardiovascular diseases are often related to genetics and lifestyle factors.

What infectious diseases should I be concerned about?

There are different kinds of infectious diseases, depending upon the pathogen that causes them. Many are caused by viruses, which are microbes that invade cells in the body and use them to multiply, producing more viruses identical to themselves. Common examples of infectious viral diseases include:

• The common cold
• Flu
• Chicken pox/shingles
• Measles
• Mumps
• Rubella
• Herpes
• Hepatitis A,B and C
• Polio
• Mononucleosis
• AIDS

In many infectious diseases, the pathogens that cause illness are bacteria. These are microscopic, single cell organisms that are found virtually everywhere. Many are beneficial to plants, animals and people, but about 1 percent of bacteria are harmful to humans, capable of causing disease. Common examples of infectious bacterial diseases include:

• Salmonella
• Chlamydia
• Gonorrhea
• Syphilis
• Lyme disease
• Tuberculosis
• Meningitis
• Strep throat
• MRSA
• Impetigo

In some infectious diseases, parasites are the pathogen that causes illness. Parasite are living creatures that need a host to survive. When that host is a person, they can develop a parasitic infection. Common infectious diseases caused by parasites include:

• Trichomoniasis
• Toxoplasmosis
• Cryptosporidiosis
• Giardiasis
• Malaria

If you suspect you have contracted an infectious disease, knowing exactly which one you have is very important to successful treatment. That's because medications used to treat these diseases typically target the specific pathogen that causes them – antibiotics for bacterial infections, for instance, or antiviral medications for certain viral infections. For this reason, infectious disease testing is typically done before treatment begins.

Laboratories generally use blood and/or urine tests, depending upon the specific disease tests performed, to detect and identify pathogens that cause infectious disease. Blood tests typically look for antibodies to certain pathogens in the blood, which can indicate infection, and urine tests generally look for specific pathogens in urine samples to confirm infection. Infectious disease panels test for several diseases at once, and may include both urine and blood tests.

How are infectious diseases transmitted?

There are several basic ways that infectious diseases can be transmitted. These include:

• Direct Contact – Person to person transmission occurs with many diseases, such as the direct transfer of viruses, germs or parasites from an infected individual to another person. This can happen when an infected person touches another person, coughs or sneezes near them, or handles an uninfected person's food or drink. Sexually transmitted diseases spread from one person to another via sexual contact. Diseases like hepatitis B or HIV, can be spread by direct contact with an infected person's blood or bodily fluids, which can occur during sex, while treating injuries, or by sharing needles during drug use. Being bitten or scratched by an infected animal or insect can also be the source of transmission of many infections, including Lyme disease, malaria and toxoplasmosis. Some infectious diseases can also be passed to unborn babies by an infected mother.
• Indirect contact – People can also become infected by contact with things that are contaminated by a disease-causing pathogen. For example, your hands can be contaminated with viruses by touching a door handle, table top or faucet handle that has been used by a person who has a cold or flu. You can pick up the parasite that causes Toxoplasmosis by cleaning a cat's litter box. Hepatitis A has been spread to customers by infected food service workers. Care givers can be infected as they handle infected bedding, clothing or other personal items.

Where can I get infectious disease testing near me?

Search for convenient infectious disease testing lab locations near you using our Lab Locator.