Pokérus
Pokérus is a virus that first appeared in the second generation games (Gold/Silver/Crystal) and on. The virus is not a bad thing for a Pokémon to have; in fact it's a good thing. When a Pokémon has Pokérus, the Pokémon's stats will become better. This is because the Pokémon will gain double EV (effort value) points. Really, Pokérus, is the quintessential condition to have when you're EV training your Pokémon. The virus does not harm or do anything to affect the way your Pokémon behaves or battles otherwise.
How to get it
The chances of your Pokémon getting the virus are very rare it must be said. According to Bulbapedia, the chances are 1 in 21,845 (Bulbapedia 2008). Here's the ways your Pokémon could catch it though:
- From a wild Pokémon. (again, the chance of this is roughly 1 in 21,845)
- From another trainer's Pokémon such as by trading.
- From one of your own Pokémon already infected with it. The virus is contagious.
- By using a Gameshark or other cheating device.
Once you have it...
You'll know when your Pokémon has Pokérus when a nurse at any Pokémon center says that your Pokémon has been infected by "small life forms" known as Pokérus. Afterwards, on the Pokémon's summary screen, you'll see the status "Pkrs". At this point, you want to spread this condition to all your Pokémon. It's easy to do: just run into some battles with your infected Pokémon. Afterwards, the virus should spread to the other Pokémon in your party. You can also deposit Pokémon into the PC Box with the virus where it'll stay in effect (Bulbapedia 2008). This is an effective way to keep the virus going.
Again, do as much training as you can with your Pokémon while it has this unique condition, for its stats will improve; especially when EV training.
Afterwards
The virus should last for a few days. Pokémon cannot re-catch it again, or spread it to other Pokémon once they've already had it. In the summary screen, you'll notice a dot (in Gold/Silver/Crystal/Ruby/Sapphire/Emerald) or a smiley face in (Diamond/Pearl/Platinum) indicating the Pokémon had the virus.
Source:
1 Bulbapedia. "Pokérus." Bulbapedia. 10 Dec 2008. 23 Dec 2008 http://bulbapedia.bulbagarden.net/wiki/Pokerus.
