Can you provide more information?
What Mac OS X version do you use, where exactly is that file located (a path can be described like this: Macintosh HD / Users / YOU / Desktop or Macintosh HD /) and is that the full content of it?
Why does it make you concerned? A .txt file is not an executable, it is just a text file.
PS: Mac OS X has currently no viruses, some malware exists though, but you have to manually install it.
PPS: Any more information you can share with us?