Myocarditis, or inflammation of the muscular walls of the heart, is most commonly caused by viruses, however, it can also be caused by bacteria, parasites, and fungi. Other causes of the condition include radiation, chemicals, cocaine use, and prescription medications.

Oncogenic Infections

Cancer often is linked to lifestyle choices (such as smoking), a person's genetic* makeup, and environmental influences. Researchers now have begun to make connections between the development of certain types of cancer and specific viral, bacterial, and parasitic infections.

Oral Infections

Bacteria and viruses usually cause oral infections. They can affect the teeth, gums, palate (PAL-it, the roof of the mouth), tongue, lips, and inside of the cheeks.


*intestines are the muscular tubes that food passes through during digestion after it exits the stomach.

Otitis (Ear Infections)

Ears have three main parts: outer, middle, and inner. The eardrum is between the outer and middle ear and is the part of the ear that responds to sound waves by vibrating.

Pertussis (Whooping Cough)

Pertussis is a respiratory disease found only in humans that is caused by the bacterium Bordetella pertussis. The first account of the infection was recorded in the sixteenth century, but it was not until the early twentieth century that B.

Pinworm Infestation

Human pinworms, Enterobius vermicularis (en-tuh-ROH-be-us ver-MIH-kyoo-lar-is), are a species of roundworm* about the size of a staple. People become infested when they swallow tiny pinworm eggs, usually after touching something that a person with pinworms has touched.


Plague is a disease caused by the bacterium Yersinia pestis (yer-SIN-e-uh PES-tis). It has been in existence for at least 2,000 years and in the twenty-first century is still found in Africa, Asia, South America, and North America.


When a person breathes, air enters the lungs and travels through millions of tiny sacs. These sacs, known as alveoli (al-VEE-o-lye), are where oxygen is transferred to the blood, which carries it to all parts of the body.


Poliovirus, part of the enterovirus* group, makes its home in the gastrointestinal* tract, but when the viral infection spreads it can destroy nerve cells known as motor neurons, which make muscles work. The damaged motor neurons cannot rebuild themselves, and as a result the body's muscles no longer function correctly.


Because of its devastating effects, rabies has been one of the most feared diseases in the world since it was first described in ancient times. A member of the Rhabdoviridae family of viruses causes rabies.

Rickettsial Infections

The diseases caused by rickettsial infections are alike in many ways. Rocky Mountain spotted fever, typhus (TY-fis), ehrlichiosis (air-lik-e-O-sis), and Q fever all have similar symptoms, including headache, high fever, and sometimes a rash.


Despite its name, ringworm is not caused by a worm but by mold-like fungi known as dermatophytes (dur-MAH-toh-fites) that thrive in the top layer of the skin, in the scalp, and in nails. Several different but related types of fungi, including those in the Trichophyton and Microsporum species, cause ringworm infection on different parts of the body.

Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF) is the most serious of the rickettsial (rih-KET-see-ul) infections, diseases caused by bacteria from the Rickettsiaceae family. These bacteria typically spread to people through blood-sucking parasites* such as ticks and fleas.

Roseola Infantum

Also known as exanthem subitum (eg-ZAN-thum SU-bih-tum), roseola infantum is an acute* viral infection that mainly affects children between the ages of 6 months and 3 years and is characterized by high fever followed by a rash. The disease stems from infection with human herpesvirus (her-peez-VY-rus) type 6 (HHV 6) or human herpesvirus type 7 (HHV 7).

Rubella (German Measles)

Rubella is caused by the virus of the same name. The word "rubella" comes from the Latin word for "little red," which originally described the infection's telltale rash.


Schistosomiasis is a parasitic disease that is not directly contagious from person to person. Five types of Schistosoma worm, also called blood flukes, can infest people and cause schistosomiasis: S.


Sepsis is caused most commonly by bacteria in the bloodstream, a condition known as bacteremia (bak-tuh-REE-me-uh). These bacteria produce toxins* that provoke a response by the body's immune system.

Sexually Transmitted Diseases

STDs can be caused by bacteria, viruses, or parasites. Although the symptoms of a particular STD depend on the specific infection, many STDs cause vaginitis (vah-jih-NYE-tis), an inflammation of the vagina often accompanied by an abnormal discharge (fluid released from the body), and urethritis (yoo-ree-THRY-tis), an inflammation of the urethra (the tube through which urine passes from the bladder to the outside of the body), which can make urination painful.