Nope, definitely no viruses. You CAN get malware from installing shady apps that have unnecessary permissions that can create backdoors to the phone to funnel your info through, but that's really about it. Torrents could make your phone slower only if it's hogging your bandwidth or if it's a poorly written app and has memory leaks or something to that affect.
Need some help, advice, something fixed? Hit me up on Hangouts @ es0tericcha0s and check out my site: http://mobilemojo5280.com
for more info!
HTC Droid Eris / Motorola Droid / Samsung Galaxy S Fascinate / Motorola Droid X / LG G2x / HTC Evo 3D (x2) / Samsung Epic 4G Touch (Sprint S2) / HTC Amaze / Samsung Galaxy S3 (International) / Samsung Galaxy Note 2 / Nexus 4 / HTC One / Samsung Galaxy S4 / Sony Xperia ZL / Nexus 5 / ? (One+1 maybe...)