Unless that is semantics? This is where we get arguing over how many angels there are on the head of a pin.

There are no known viruses that affect Mac OS. The main concern for Macs really is passing on viruses to Windows users via Mail, not actually catching them. Macs don't get the firmware virus because the Virus uses Windows' Autorun, again something MacOS doesn't have. These however do not work on Macs as MsOffice for Mac does not have macros and a converted MsOffice document can't pass them on, the conversion simply works on the text. Microsoft documents have vulnerabilities in the macros embedded. I think you are suspecting either a Virus via the FlashDrive firmware, something that existed many years ago, or have a Microsoft document on the drive. So please do not perpetuate a dangerous myth. I regularly run a sweep with VirusBarrier Pro which generally finds something, mostly Adware in the Browsers.

Apple keeps issuing updates to correct any vulnerabilities for a reason and has been criticised by industry experts for on occasions not fixing problems for extended periods of time, but given a low probability of being attacked does not equal no probability, precautions are still necessary. There are viruses and malware for MacOS it is just that the protection is pretty good and they rarely get any traction.