Let's be clear you are worried about a virus and not something you must install by choice.
"A computer virus is a computer program that can replicate itself and spread from one computer to another. The term "virus" is also commonly, but erroneously, used to refer to other types of malware, including but not limited to adware and spyware programs that do not have a reproductive ability."
Since we've yet to see a virus on these, what would an antivirus do except remove money from your wallet.
One of my friends sent out an email to several people with an attachment, but very little text. I was on my phone and downloaded the attachment. However, I realized right after the "suspicious" nature of the email and deleted the attachment as well as the email. Do I have anything to worry about, if I didn't open the attachment? Are there any reliable anti-virus software for Android?