Make that 3.
There are many forms of ‘Malware’ that can affect a computer system, of which ‘a virus’ is but one type, ‘trojans’ another. Using the strict definition of a computer virus, no viruses that can attack OS X have so far been detected 'in the wild', i.e. in anything other than laboratory conditions. The same is not true of other forms of malware, such as Trojans. Whilst it is a fairly safe bet that your Mac will NOT be infected by a virus, it may have other security-related problem, but more likely a technical problem unrelated to any malware threat.
You may find this User Tip on Viruses, Trojan Detection and Removal, as well as general Internet Security and Privacy, useful:
The User Tip (which you are welcome to print out and retain for future reference) seeks to offer guidance on the main security threats and how to avoid them.
Make that four.
If you have any commercially advertised/available antivirus software installed on your Mac, completely uninstall this per the instructions on the AV developer's website.
Antivirus software can slow down the normal operation of OS X and can negatively affect OS X performance and operation.
Do you have apps like MacKeeper or any other maintenance apps like CleanMyMac 1 or 2, TuneUpMyMac or anything like these apps, installed on your Mac? These types of apps, while they appear to be helpful, can do too good a job of data "cleanup" causing the potential to do serious data corruption or data deletion and render a perfectly running OS completely dead and useless leaving you with a frozen, non-functional Mac.
Plus, these type of apps aren't really necessary. They really aren't.
There are manual methods to clear off unnecessary data off of your Mac that are safer and you have complete control over your Mac and not just leave a piece of auto cleaning software in charge of clearing off data off of your Mac.
Their potential of causing OS X issues outweighs the implied good and benefits these types of hard drive or memory "cleaning" apps are written to do.
Plus, the software companies that write these apps make it hard to easily uninstall these apps if something DOES go wrong and these apps work in a way where you have no recovery or revert function to return your Mac back to its former, working state in the event something does go wrong.
It is best to never, EVER download and install these types of apps.
The risk to your system and data is too great a risk!
Search the web to learn how to correctly and properly uninstall these kinds of apps.
They all uninstall differently.