A Sim with very high logic can use the Biotech Station to deliberately make a virus. Biotech Station can cut down the resting time needed to be cured of a sickness, though a Sim with low logic skill and/or who is in a bad mood can create a virus instead. The White Potion made with The 'Concoctanation Station' chemistry set can cure a sickness.
White potions will cure the guinea pig sickness, but otherwise have no effect if drunk by a healthy Sim. Orange potions turn Sims invisible, purple potions turns your Sim into a monster, and yellow potions reverse your Sim's traits. Red potions will make a random Sims from the neighborhood fall in love with the Sim who consumes it. Light green potions will decrease all your Sim's motives. Sims can create one of eight different colored potions at the buyable chemistry set.