You have a better chance of running into a shiny than running into a wild pokémon with pokérus. Still, this pokémon virus has huge benefits and is sought after in the competitive and casual communities alike. In the game, an infected pokémon will gain double the stats every time it levels up. But what does this mean in a more physical sense?
To start, let’s talk about viruses. We know Pokérus is a virus, which to be honest doesn’t tell us a whole lot. Viruses are as diverse and as crazy as anything, infecting you with everything from colds and flus to rabies and ebola. Their appearances vary as much as their symptoms, and many of them look very alien.
So what exactly is a virus? Cells in your body, along with bacteria, are stand-alone living entities able to eat, grow, and reproduce. Viruses are something different altogether. Viruses are little envelopes full of genetics: a protective protein coating surrounding single or double strands of DNA or RNA. By themselves, viruses are not able to function. This is why they need to infect a host cell: to live and reproduce.
They do this through the lytic cycle. Basically, a virus will invade a host cell, and take over the cell’s machinery. The virus will trick the cell into working for them: they turn the host cell into little virus-factories, building more and more viruses with the cell’s machinery which then can go and infect new cells.
This is why viruses are contagious. If someone sneezes on you, or you breathe in a virus, it can start entering your cells and start reproducing right away. This is how pokérus is spread. However, it should be noted that a lot of viruses are species-specific; humans cannot be infected with pokérus.
However, pokérus is unique due to its positive effects. Viruses are generally not something you want. For example, a runny nose: cold viruses will infect and kill cells in your nose, and with less cells lining your sinuses, fluid flows freely. Fevers are your bodies response, trying to kill the virus by literally turning up the heat.
So somehow, instead of destroying and taking over host cells, Pokérus viruses benefit them. Pokérus doesn’t infect and kill a pokémon’s cells; it strengthens them. Exactly how is widely up to interpretation. What does a stat boost in-game equate to in real life?
Maybe the pokémon is buffed up as if on steroids. This would mean that pokérus increases protein production and ATP levels. Or maybe, Pokérus just helps a pokémon grow strong, by enabling them to more easily break down and use vitamins like calicium. It all has to do with whatever the virus’ DNA/RNA strand tells the cell to do. Most viruses just tell the cell to build more viruses, but the pokérus DNA must be like a motivational speech for a cell. And then it replicates and spreads, of course.