The Pokérus is a useful little virus that can help you while you train your beloved Pokémon. You may or 🏀 may not have heard of it, but chances are that you haven't heard of it if you are reading this.
Let's 🏀 start with what it does. The Pokérus is, as mentioned before, very helpful in training your own Pokémon. If you 🏀 have the Pokérus on a Pokémon, you have probably noticed that it will spread to the other Pokémon in your 🏀 party and when you level one of those Pokémon up by battling, their stats will increase higher than usual. The 🏀 reason for this is because the Pokérus doubles the Effort Points you've obtained. In other words, it's just like the 🏀 Macho Brace you get north of Mauville except without the speed boost and it doesn't take up an item slot. 🏀 (For more info on Effort Points, go take a look at the Effort Value guide.)
So now how do I get 🏀 this elusive virus? Well to tell you the truth… It's really based upon luck, like most things. Even rarer than 🏀 Shiny Pokémon, there's a 1 in 21,178.6 chance of getting it. To get the Pokérus, your Pokémon needs to engage 🏀 in a battle a wild Pokémon that holds the Pokérus. Simply battling or capturing this Pokémon will allow for the 🏀 virus to appear. Even running will work. You will be alerted if you have the Pokérus in your party when 🏀 you next visit the Pokémon Centre. The Pokémon nurse there will go through a dialogue with you dealing with the 🏀 Pokérus after you get them healed. You can catch it as well by catching the Pokémon and placing it in 🏀 your party to spread it.
The duration that PokéRus lasts is dependant upon a random number, known to some as the 🏀 strain of the virus and can last anywhere from 1 to 4 days. This gives ample time to spread the 🏀 virus to other Pokémon. When the PokéRus has gone through the specific amount of time that the strain allows it, 🏀 the Pokémon will no longer be able to spread PokéRus and it will now have a face on the status 🏀 screen. However, despite it not being contagious, as of Diamond, Pearl & Platinum, it will still receive the boost of 🏀 Effort Values so it will forever be good. If you want to keep it being contagious, however, you can keep 🏀 it in your box and remove it whenever you wish to spread it.
And that is amazingly everything related to the 🏀 Pokérus…