Based on Virginia Dept of Health website stats - the dirtiest Subway in Fairfax County is...
There are 78 Subway restaurant in Fairfax County. Reading through the information available onlone here,
http://www.healthspace.com/Clients/VDH/Fairfax/Fairfax_Website.nsf, I was impressed to discover that the majority of them have zero health inspection violation.
A few more had a handful of minor infractions - stuff that needs to be corrected but doesn't directly affect your food safety.
Also, a few had one or two critical violations. However, there was a tie for first place for the most number of critical violations at 4. Still not as bad as Tippy Taco's (Centreville) last inspection with 6 critical violations.
The two dirtiest Subway locations are:
7868 Richmond Hwy, Alexandria (4 critical, 1 minor)
262-A2 Cedar Lane, Vienna (4 critical, 1 minor)