Pokérus is a beneficial virus that sometimes infects your Pokémon after defeating a wild opponent.
This virus helps Pokémon strengthen faster by doubling their Stat Experience acquisition rate. An infected Pokémon’s stats increase more with each level gained.
A Pokérus infection lasts somewhere between one and four days. During this time the virus might spread to other Pokémon in the party. After this time, the virus stops being contagious, but the affected Pokémon keeps the increased Stat Experience growth rate forever.
How To Get Pokérus
Pokémon get Pokérus from infected opponents in the wild. You can tell they have it by checking their Stats screen.
Infected Pokémon have the word “Pokérus” in the Status section, where you’d normally see a status ailments (like Poison or Sleep).
The nurse in the next Pokémon Center you visit will also inform you of “tiny lifeforms” on your Pokémon the next time you heal.
But here’s the downside:
The chances of your Pokémon getting Pokérus from a wild opponent is 3/65,536.
Important: Pokérus infection is only possible after reaching Goldenrod City for the first time.
To put things into perspective, you’re almost three times more likely to find a Shiny Pokémon than to get Pokérus.
Regrettably, there’s no way to improve your odds. Finding someone willing to gift or lend you a Pokémon with Pokérus is much easier.
Alternatively, keep fighting low-level Pokémon you can defeat in one move. It’s the fastest way to get through 22,000 Pokémon.
How To Spread Pokérus
Infected Pokémon have a 33% chance of spreading the virus to other Pokémon in your party at the end of every battle.
The virus infects one adjacent new Pokémon at a time. After a few battles, your entire party should be infected.
Tip: Eggs can also become infected by Pokérus.
Once you get at least one infected Pokémon, making “back-ups” is essential so you never lose access to Pokérus. Infected Pokémon only get cured at midnight. If the Pokémon isn’t in your party at the time, it can’t overcome the infection.
That means storing an infected Pokémon in a Storage Box will indefinitely freeze the condition.
Just withdraw the Pokérus carrier and keep it in your party for a few battles when you need to infect another Pokémon.
Note: Pokémon in a Box in Bill’s PC won’t spread the virus to other stored Pokémon. It can only spread in your party.
Pokémon will overcome the Pokérus infection by themselves after one to four days.
Tip: The same “strain” of Pokérus will always last the same amount of time. If your first infected Pokémon had it for three days, it will always last three days.
The game only counts a day as “passing” if the Pokémon is in your party when midnight strikes. Pokémon can’t get cured while in storage.
You’ll know a Pokémon has overcome Pokérus because the condition no longer appears as a status ailment. Instead you will see a small black dot on the Pokémon’s status screen right above the HP bar.
This dot indicates that the Pokémon has had Pokérus in the past and, therefore, keeps the enhanced growth effect.
Strain 0 Pokérus
There’s a minuscule chance of your Pokémon becoming infected with a different type of Pokérus than usual. We’ll call this “Strain 0”.
This Pokérus variant works almost the same as regular Pokérus, except for one thing:
The increased Stat Experience growth goes away when cured.
You can check the cured Pokémon’s status screen to determine whether they’ve retained the increased Stat Experience growth. If there’s a dot above the HP gauge (like pictured above) then it still has the benefits of Pokérus. If not, you’ve got Pokérus Strain 0.
In this unfortunate case, you’ll have to keep re-infecting your Pokémon as you train it.