I gave a handjob to a new partner recently. My clothes stayed on and he did not touch my genitals at all. I did not come into contact with any semen and did not touch myself afterwards. What are the chances of catching something?
slim to none.
Not very likely. Even with dirty hands. Its possible to cause other types of infection though. For example: if you fingered a girl that had an STD and then fingered another girl straight after the first one without an STD, the second girl would get an STD through that.