Salmonella
A bacterium that can cause severe diarrhea, fever or bacteremia; can be spread in many ways including from undercooked poultry (turkey and chicken), raw eggs, and pets (such as turtles), as well as from person to person; antibiotic treatment is indicated in certain circumstances.

Scarlet fever
A streptococcal infection accompanied by a generalized rash.

Scoliosis
Abnormal curvature of the spine; usually of unknown origin; causes serious problems if left untreated.

Seizure
Convulsion; violent involuntary jerking of the muscles; caused by an abnormal electrical discharge in the brain; recurrent seizures are known as epilepsy.

Septicemia
Sepsis; formerly known as blood poisoning; serious bloodstream infection caused by bacteria and their toxins; requires prompt antibiotic therapy to prevent shock and death.

Sexually transmitted disease (STD)
Any infectious disease that is transmitted through sexual intercourse or other intimate sexual contact; important STDs include chlamydia, gonorrhea, syphilis, herpes simplex virus and HIV.

Shigella
A bacterium that can cause bloody diarrhea and high fever; treatable with antibiotics.

Shingles
Herpes zoster; reactivation of varicella zoster virus in a person who has had chickenpox many years earlier; marked by a cluster of painful skin lesions that resemble those of chickenpox; may respond to antiviral medications.

Shock
Severely inadequate delivery of oxygen from the bloodstream to the tissues of the body; marked by pale and clammy skin, low blood pressure, rapid heart rate; causes can include blood loss, poor heart or blood vessel function, and infection; if left untreated, can result in death.

Sickle cell anemia
A genetic disease, primarily of people of African or Mediterranean origin, causing deformation of the red blood cells so that they are curved and look like a sickle; marked by many features including anemia, increased risk of infection and pain.

Sinusitis
Inflammation of the sinuses; usually caused by bacterial or viral infections.

Smegma
A normal thick, cheesy secretion that collects around the clitoris or the head of the penis.

Spasticity
A state of increased muscle tone and exaggerated reflexes, often causing stiff and awkward movements.

Spina bifida
A type of myelodysplasia; a congenital defect characterized by improper closure of the bones that surround the spinal cord (vertebrae).

Splenomegaly
Enlargement of the spleen.

Sprain
An injury to, but not actual tearing of, the ligaments of a joint; typically associated with pain, swelling and bruising; caused by excessive stretching.

Strep throat
An infection of the back of the throat (pharynx) with the group A streptococcus; antibiotic therapy is indicated to help prevent rheumatic fever.

Stridor
A harsh sound made when a child with an obstructed throat or trachea (tube leading down to the lungs) breathes in; the obstruction may be caused by allergic reactions, trauma, foreign body aspiration, croup or other infections.

Sudden infant death syndrome (SIDS)
The sudden death of a young infant from unknown causes.

Swollen glands (swollen lymph glands)
Lymphadenopathy.

Syncope
A fainting episode; usually caused by temporarily diminished flow of blood and oxygen to the brain.

Syphilis
A highly contagious sexually transmitted disease that can infect, and lead to serious damage of, any and all organs in the human body; caused by the spirochete (a kind of bacterium), Treponema pallidum; antibiotic treatment is essential to prevent long-term serious complications.

T

Tendonitis
Inflammation of the fibrous cords that attach muscles to bone (tendons).

Tetanus
A vaccine-preventable disease characterized by painful spasm of the muscles of the mouth (lockjaw), and then other muscles of the body; caused by a neurotoxin produced by the bacterium, Clostridium tetani; prevented by routine childhood immunizations (the "T" in DTaP) and booster shots.

Thalessemia
A group of hereditary blood disorders in which the body produces abnormal hemoglobin; some forms can cause significant anemia.

Thrush
Yeast infection of the inside of the mouth commonly seen in normal babies; marked by whitish patches that cannot be scraped off of the tongue, roof of mouth and inside lining of the cheeks; caused by Candida albicans; treatable with antifungal medications.

Tonsillitis
Inflammation of the tonsils (the lymphoid tissues in the back of the throat); typically caused by bacterial or viral infections.

Tourette's syndrome
An inherited, chronic disorder marked by tics such as eye blinking, facial grimacing, head jerking, or repetitive throat clearing, grunting or words; in some cases marked by repeated involuntary use of obscene language.

Tuberculosis (TB)
A highly contagious disease that causes infection in the lungs, lymph nodes and other organs; caused by the bacterium, Mycobacterium tuberculosis; usually requires prolonged treatment.

U

Ulcer
A breakdown of the skin or mucosal surface (such as the lining of the stomach), usually accompanied by inflammation; can be caused by infection, chronic irritation or inadequate blood flow to the area.

Urinary tract infection (UTI)
An infection of the bladder or kidneys.

Urticaria
Hives.

V

Vaginitis
Inflammation of the vagina with irritation, pain and/or discharge; can be caused by infection, irritation or a foreign body.

Varicella
Chickenpox.

Virus
A tiny infectious agent that can survive only in the cells of a living host; antibiotics (antibacterial agents) have no effect, but some effective antiviral medications are available.

W

Wart
A rough, heaped-up lump on the skin; caused by viral infection; treatment depends on the type of wart and its location.

Wheezing
The high-pitched whistling sound made by air passing through a narrowed airway; most commonly heard in asthma, bronchiolitis, foreign-body aspiration, and other conditions associated with narrowing of the small respiratory tubes (bronchioles).

Whooping cough
Pertussis.

Y

Yeast infection
A mild fungal infection, usually of the mouth, diaper area or vagina.