Task List/pkrs lv5
Wow! Seems like you need to have an extremely low immune system to catch PokéRus 500 times. You should still be clicking the host though, it's that... good kind of sickness.
Click the "PokéRus" button in the top right corner beneath the bonus counters to go to the host's page.
For more information on PokéRus, check the Wiki.