Ms. Hoover announces to her class that she will be out sick for a while because she has Lyme Disease. When Ralph asks about Lyme Disease, Principal Skinner explains how the disease is contracted and spreads throughout the body.

Beakman acts like he is a patient with a sore throat and goes to the doctor. The doctor explains lymph nodes and all of the symptoms of strep throat. Then he explains that strep throat is detected using a test and treated with antibiotics.

A worldwide epidemic starts when humans cut down trees in an area inhabited by bats, forcing them to relocate. One bat carrying the virus dropped a piece of banana into a pig pen. One pig consumed the banana piece, and when it was slaughtered, the virus spread to the butcher's hands. The butcher did not wash his hands before he went to shake the hand of a guest, thus spreading the disease to the guest, who then spread it to other people.

Ebola is a rare, but extremely dangerous disease. Find out how many strains of Ebola exist, how the Ebola virus attacks its host, and the symptoms caused by the virus.

Dr. Kelso explains how infection can spread.