EV's, PokéRus and Power Items

Effort Values
Effort values, often abbreviated as EVs, are an important part of Pokémon training to consider.
While raising a Pokémon's level is a very important part of its training, making sure that a Pokémon gains effort points in the correct stats is just as important to making your Pokémon the best it can be.

As the basic EV system goes, each Pokémon gives out either 1, 2 or 3 effort points, depending on its species, in a particular stat (HP, Attack, Defense, Special Attack, Special Defence, or Speed). With these effort points, a Pokémon would get stronger in a specific stat by battling the same kind of Pokémon over and over.
For example, Starly gives out 1 EV in speed, therefor battling Starly after Starly would cause your Pokémon to eventually have a higher Speed.
At level 100, a Pokémon's stats will be one point higher in a specific stat for every four effort points gained in that stat.

Effort training like this is limited to 510 effort points total, with 255 effort points being the maximum for an individual stat. What I mean by this is that two stats could be maxed out (at 255 for lets say, Attack and Speed). 255+255=510 EVs. Or, two stats at 252 (with 252 being the highest number evenly divisible by four) and one other stat at 6 EVs. 252+252=504+6=510 EVs.

Here is just a short list of Pokémon that give out 1 EV in each stat.





PokéRus
The Pokémon Virus, or PokéRus for short, is a Pokémon enhancing virus.
In the game, you would actually have a 1 in 21,845 chance to become infected with the virus. This slim chance means that you would most likely never encounter it.

After being infected, a Pokémon's status will read "Pokérus". When next you visit a Pokémon Center, the nurse will notice that there are "small life forms" on your Pokémon.

A Pokémon with the PokéRus will infect other Pokémon in your active party while walking, battling, or healing at a Pokémon Center.

The PokéRus will not infect other Pokémon if it's stored in the PC, and will become immune while in your party after about 24 hours. After recovering from the virus, a little smiley face appears on the Pokémon's status screen indicating that it is immune to the virus and impossible to reinfect.

The virus is actually a good thing. The PokéRus doubles the Effort Values (as mentioned above) received from battles. This causes the stats of a Pokémon to grow twice as fast while still leveling up at a normal rate.

After a Pokémon's immune system fights off the virus, it will still be able to gain double Effort Values permanently. However, it will not be able to infect other Pokémon with the beneficial enhancement virus.


Power Items
Power Items or EV-enhancing items are items which enhance the EVs gained when a Pokémon is defeated. All of them reduce the Speed of the Pokémon holding them in battle while they are being held.
All of these items (with the exception of the Macho Brace, which I'll get to later) can be purchased at the Battle Tower for 16 BP each. All EVs gained with any item will double if your Pokémon is affected by the PokéRus.

Power Weight
Promotes HP gain by adding 4 EVs in HP on which ever Pokémon is fought.

Power Bracer
Promotes Attack gain by adding 4 EVs in Attack on which ever Pokémon is fought.

Power Belt
Promotes Defence gain by adding 4 Evs in Defence on which ever Pokémon is fought.

Power Lens
Promotes Special Attack gain by adding 4 EVs in Speical Attack on which ever Pokémon is fought.

Power Band
Promotes Special Defence gain by adding 4 EVs in Special Defence on which ever Pokémon is fought.

Power Anklet
Promotes Speed gain by adding 4 EVs in Speed on which ever Pokémon is fought.

There are 6, one for each specific stat, and they all add 4 EVs to that one stat they are for, regadless of what Pokémon is fought. In addition to the 4 EVs, which ever Pokémon you fought, you also get the EV from that Pokémon as well.

Macho Brace
The Macho Brace is a special item in that it doubles the Effort Values you get, and then that in turn can be doubled again by the PokéRus.
The only way to get this item is as a gift from boy in Pastoria City after showing him all three forms of Burmy.