A state of polywater intoxication (sometimes referred to as the Psi 2000 intoxication, the Psi 2000 virus or the Tsiolkovsky infection) was an affliction caused by polywater molecules, first noted on Psi 2000. It was spread through contact with infected perspiration or blood. The main symptom of the intoxication was the suppression of inhibitions, resulting in an effect that appeared much like drunkenness.
It first affected the members of a Federation science team stationed on the planet from which it was named in 2266. The transmission of the affliction was water-based, caused by huge shifts in gravity, resulting in complex strings of water molecules that had the ability to propagate themselves, much like a very simple version of a virus. Polywater-infected blood also demonstrated the ability to melt itself from a frozen state, move along surfaces and jump for short distances to infect a host.
The disease was spread to the crew of the USS Enterprise (which was conducting a study of Psi 2000's disintegration). As a result, the ship was nearly destroyed when the affected Lieutenant Kevin Riley disabled the ship's engines; a disastrous move aboard a ship in orbit around a disintegrating planet. The cure was developed by Dr. McCoy. (TOS: "The Naked Time")
Ninety-eight years later, the SS Tsiolkovsky was studying the collapse of a red giant into a white dwarf, which created similar gravitational shifts that also resulted in another case of mass intoxication. The USS Enterprise-D arrived to answer odd messages broadcast by the crew of the Tsiolkovsky. However the crew was already dead. An away team, led by Commander William T. Riker, established that much of the crew had frozen to death because they had lowered the environmental controls to well below safe temperatures. The rest of the crew, as Lieutenant Commander Data ascertained, were killed when an emergency hatch was blown, blowing them out into the vacuum of space. Lieutenant Geordi La Forge was the first Enterprise-D crewman to become infected when a polywater infected fully clothed woman taking a shower fell on him. Despite an attempt at quarantining him, La Forge managed to infect several Enterprise-D personnel. Initial symptoms of this new strain appeared to be excessive perspiration and a feeling of high body temperature, as well as the lack of inhibition shown amongst the crew of the original Enterprise.
Data also became infected, even though he was an android. Captain Picard thought this could not be possible. Soong-type androids were incapable of alcohol intoxication, yet components in its processing systems were apparently susceptible to disruption by polywater intoxication. (TNG: "The Outrageous Okona", "The Naked Now")
The Enterprise-D computer database held the formula for the cure used aboard the NCC-1701 Enterprise. However, this was not successful in treating the intoxication. Due perhaps to the higher gravity of the star, this intoxication was more severe, requiring Doctor Beverly Crusher to create a broader remedy. (TNG: "The Naked Now")