Sex is not the issue; it's everything else
[QUOTE=Mrlefty;4711890]It's not communicable in doggie style.[/QUOTE]The sex is a side show re the virus. The real issues are door knobs, sheets, her clothes, water faucet, money and any other surface you touch in the FC long before you even stick your dick in the SB.
The SB could be clean as heck, but the last SD could have laid down tons of virus on her clothes and that's all it takes. It can live for days on many surfaces. People take baths daily, but how often do they wash clothes and wipe down other surfaces? Therein lies the issue.
As for an SB who hosts, assume every surface any other SD has touched before you is a potential infection source.