How does yahoo e-mail account get infected by virus?

How could we know that the emails contain virus while checking mails on Yahoo?

• This question may sound little bit silly, however, i still wonder if pc would get infected varied virus while clicking unknown mails from Yahoo email account or accounts. No offense give though.

• Answer:

  I have virus protection, Norton that tells me, Maybe this can help you, I went to CONTACT YAHOO CUSTOMER CARE, then clicked on LIVE CHAT, told them my problem and they switched me back 5 to10 min. total, no problem! You can also call Yahoo USA, but you will wait forever! 1-866-562-7219 Don’t forget to vote for best answer. Also I give free info. I answer Q’s that I know about, I have been put down for - I do not socialize on line, no contacts - not my thing. I have better things to do, like socialize physically in real life… Anyway Good Luck!