In this Article

What is an Infectious Disease?

Infectious diseases are diseases caused by germs. Germs are tiny living things that are found everywhere in our environment, and in and on our bodies. Your child can get infected by touching, breathing, eating, or drinking something that contains a germ, or by insect and animal bites, kissing, and sexual contact.

There are four main types of germs:

  • Bacteria [baj-TEER-ee-uh]. For example, bacteria, like some types of Streptococcus can cause skin infections, ear infections, and sore throat (“strep throat”).
  • Viruses [VIE-ruhs-uhs]. Viruses include the germs that cause the common cold, influenza (“flu”), and a common stomach infection.
  • Fungi [FUHN-jahy]. Fungi cause head ringworm, body ringworm, “athlete’s foot,” and “jock itch.”
  • Protozoa [proh-tuh-ZOH-uh]. Protozoa are responsible for causing as Giardia [jee-AHR-dee-uh] infections, cryptosporidiosis [krip-toh-spohr-i-dahy-OH-sis] (also known as “crypto”), and malaria [muh-LAIR-ee-uh].


The symptoms depend on the type of disease and the germ that caused it. Germs often cause symptoms that allow them to spread, such as a runny nose, cough, diarrhea, skin rash, or oozing body fluids. Some infectious diseases may have no symptoms.

When to See a Doctor

See a healthcare provider if your child has:

  • A long-lasting or high fever. Any child under three months with a fever of 100.4 F (38 C) or higher; or a child 3 to 6 months with a fever of 101°F (38.3 C) or higher; or a child over 6 months with a fever of 103 F(39.4 C) or higher should see a doctor.
  • Any fever with a sore throat and lasting more than one to two days.
  • A fever and pain when urinating.
  • Trouble swallowing.
  • A fever with a headache, stiff neck, or skin rash.
  • Trouble breathing.
  • An animal bite.