According to the World Health Organization (WHO), infectious disease are caused by pathogenic microorganisms (bacteria, viruses, parasites, or fungi) that spread directly or indirectly from one person to another.

The most common infectious diseases are the common cold, flu, strep throat, the stomach flu, and urinary tract infection (UTI). Depending on the type of infectious disease you might in contact with, the symptoms can vary. For example, symptoms for the common cold include: runny or stuffy nose, sore throat, congestion, sneezing, slight body aches, and a low-grade fever.

Listen in as Jason Newland, MD, Washington University pediatric infectious disease physician at St. Louis Children’s Hospital explains what infectious diseases are, the warning signs/symptoms and when you should seek medical treatment.