My s3 won't connect to any wifi!

My s3 never gave me problems, i have 2 years with the cellphone and it worked perfectly but now it started to happen that it won't connect to any wifi. I tried with my house wifi and i thought that maybe was the wifi that wasnt working well, but then i went to my best friends house and t didnt connect neither, went to my cousins house and guess?? Neither, nothing!! i tried to do somethings i found on the internet but nothing works :/ i started to think that maybe is a virus causing this??! i don't know what to do!! HELP.