Gorn virus

The Gorn Virus was an unnamed pathogen that infected several Starfleet and Vulcan personnel including Spock.

Transmission
The virus was transmitted via injection. A Gorn drone would approach the victims from the front, grab them from behind with extendable arms, and panels would open up to reveal a large bore needle that was inserted into the victim's spinal column.

Symptoms
Symptoms of the virus included oozing fluid similar in appearance to Gorn blood (perhaps the unknown toxins McCoy identified early on), as well as a compulsion to seek and attack friendlies such as Kirk and Spock. Weapons included firearms, metal bars that appeared to have been scavenged from their ship or station, and, in Spock's case, fists.

The victims, while unable to control their actions, seemed to realize that they were doing something wrong, as they would frequently call out to alert others to watch out for them.

Antidote
The antidote for this virus was synthesized by McCoy, who instructed Kirk and Spock to release it in the atmospheric generators. This ensured shipwide dispersal. The antidote was successful in curing the virus. However, the Gorn didn't seem to care for it, according to Scotty.

Victims
Victims of this virus included Vulcans on Helios-1 and New Vulcan, personnel on Frontier Starbase 17, crew members of the Enterprise, and Spock. Under its influence, Spock got into a fistfight with Kirk, who kept him at bay long enough to allow Sulu to pilot the shuttle into the arena. There, McCoy shot Spock with a dart gun loaded with the antidote. Spock's recovery was almost instantaneous.