I appreciate this topic is a well worn path and recently debated, but I always remember a bit of advice given to me by a GUM senior nurse, who was trying to calm my anxiety ( i'd got myself tied up in the all the conflicting advice that's on the web)
He said ' why do you think a WG wants to catch an STD? We get loads in here for regular checks and they go to great lengths to avoid getting any infections. It's bad for business and they lose money, because they can't work. And they have families too, they don't want to infect their partners,kids etc...'
He went on to add that seldom did WGs test positive for anything and a much great risk was sex with a civvie girl...
Having chatted to one of my regular punts, they concurred with these views. One said she carried out pre OWO visual checks of cocks, including feeling the temp, apparently an over warm cock is a sign of infection. She also does a little squeeze, to check for pus and get the foreskin back to check for any other signs. She has a good smell too, for infection. Always gets punter to shower and get completely naked, so she can check the whole body. All of this fast and very subtle, I hadn't even noticed this until she told me.
For the record, i've been punting for 20 years, doing OWO and giving occasional RO and never caught a cold. However, the anxiety never really goes away completely and I reckon it's time to rubber up for oral for me from now on.