Virus

A Virus is a germ enemy found in the Dr. Mario series. The Viruses started attacking at Mushroom Kingdom Hospital. During this time, Dr. Mario was on the scene to contain the Viruses in glass jars and eliminate them using Megavitamins.

Viruses come in three colors: red (fever), blue (chill), and yellow (weird). To defeat a Virus, Dr. Mario must line up three pills of the same color next to the Virus of that color. The Virus, along with the Megavitamins, will then disappear. After clearing one jar of Viruses, Dr. Mario will move to the next one (with each jar containing increasingly more Viruses).

The Viruses appeared as the main antagonists in Nintendo Comics System's adaptation of Dr. Mario entitled "The Doctor Is In... Over His Head". It was this appearance that named the Red Virus Fever, the Blue Virus Chill, and the Yellow Virus Weird.

In the same episode, the Viruses were given special powers: Chill could manipulate the cold, Fever could control heat, and Weird could forcibly morph others into different shapes and creatures.

Two Viruses can briefly be seen inside Bowser's stomach in the Club Nintendo comic "Süße Weihnachten". They symbolize his sickness after having eaten too much.

Viruses also appear in Mario & Luigi: Superstar Saga. In this game, Viruses roam the halls of Woohoo Hooniversity, Cackletta's temporary base-of-operation. Viruses appear in all three colors and attack in groups. However, in this game, Viruses can change color. In fact, when hit by Mario or Luigi, a Virus will assume a different color. When all the current Viruses in-battle match in color, they will be instantly destroyed, somewhat similar to the way they are defeated in Dr. Mario.

In Mario Kart Arcade GP the item, Driver Virus, is a Blue Virus. In this game, the Virus has swirly eyes.

The Blue Virus makes a minor cameo in Mario & Luigi: Bowser's Inside Story. After knocking out all the body segments of a Toothy, the Toothy attacks by spitting out a Blue Virus holding a spear to attack the player.

Trivia

 * A trophy of the Viruses appeared in Super Smash Bros. Melee and are mentioned in Dr. Mario's trophy. Stickers of the Viruses also appeared in Super Smash Bros. Brawl.
 * The Viruses make a cameo in the Nintendo Monopoly.
 * The Viruses in the mini-game Dr. Wario appear slightly different than the ones in Dr. Mario.
 * In Mario & Luigi: Bowser's Inside Story, in Toadley Medical Clinic's lobby, there is a sign on the wall that shows a blue Virus in a red circle with a "/" through it (similar to a "no smoking" or "no pets" sign).
 * In the same game, the Toothys at Plack Beach spit blue Viruses.
 * Of all the Viruses, Blue Virus is the one with the most appearances, and cameos.
 * In Mario & Luigi: Superstar Saga different hand powers are shown to have different effects on the Viruses.
 * Thunderhand Heals the Blue Virus while it counts as a critical hit on a Red Virus. and the opposite is true with the Firebrand. However both hand powers actually heal the Yellow Virus.

Trophy Information from Super Smash Bros. Melee
''These contagious viruses make life difficult for Dr. Mario. They infect everything they come into contact with, and the good doctor must attempt to neutralize them with his trusty megavitamins. Dr. Mario can stop these pesky germs by lining up the megavitamin capsules of the same color with the nasty microorganism.''