What's the fastest way to spread Pokérus?

Question

After completing Lana's challenge in Pokémon Sun, I went to the Pokécenter to heal my team. That's where the nurse told me that one of my Pokémon had Pokérus. Apparently, my Dartrix had somehow caught it. Since Pokérus is actually beneficial and quite rare (1/3 the chance of encountering a shiny Pokémon), I decided to spread it among all my Pokémon.

Apparently, Pokérus only spreads from one Pokémon in my team to whichever is positioned next to it. In other words, I only need two infected Pokémon in my team to infect the entire team. One in the upper right position (2nd), and one in the lower left (5th). Therefore, I can infect 4 Pokémon in between two Pokécenter visits at most.

However, it seems that the rate of spreading is not consistent. Sometimes, I can infect the entire team by beating a single wild Pokémon, and sometimes it can take dozens of such encounters.

I was wondering if there was a faster way to spread Pokérus among my team. For instance: Do I even need to battle at all? Can I just flee instead of fighting? Do I need to battle stronger Pokémon, or are weak ones good enough? Should I find trainers instead of going for the wild ones?

While I'm personally more interested in Sun & Moon, answers concerning other generations are welcome as well.

Answer 1

As far as I'm aware, the mechanics of Pokerus haven't changed in Sun/Moon (or really ever). Technically, though, they might have, so this answer is only definitely accurate for games up to sixth Gen.

• Pokerus may or may not spread based on a call to the RNG (so based on chance) after any battle, regardless of how the battle ended.
• It will only spread to adjacent Pokemon. I've never heard of nor experienced a case of Pokerus spreading further than one Pokemon per battle, although it does always spread in both directions if possible.

Based on this, the fastest way to spread the virus is to keep Pokemon with active Pokerus in slots 2 (top right) and 5 (bottom left), while putting the Pokemon you want to infect in slots 1, 3, 4 and 6. Encounter a wild Pokemon, flee, and check to see if it spread. If it did, it should have spread from 2 to both 1 and 3, as well as from 5 to both 4 and 6, so your entire team should be infected. Replace 4 Pokemon, make sure the infected ones are in slots 2 and 5, then repeat. If it didn't, encounter a new wild Pokemon, and so on.

It should be noted that you can infect a maximum of 5 Pokemon in between PC visits, but only with 2 or more battles (based on the RNG result). Basically, you put the one infected Pokemon in any slot, battle until it spreads Pokerus, then put two infected Pokemon in slots 2 and 5 and battle until it spreads again. This way, you will have infected 5 Pokemon in 2 or more battles without going to a PC in the meantime. This trades off visits to the PC with additional battles, so it's slower if you have access to a PC near tall grass (the PC in the day care is good for this purpose in most games). Especially early in the game, though, it might be worth it to maximize spreads per PokeCenter travel rather than spreads per battle.

Make sure you always have at least one Pokemon with active Pokerus in a PC box when the date rolls over since that's when the timer ticks down on everything in your team and the Pokemon might lose the ability to spread Pokerus.