I think just for health reasons a person should masturbate at least 1-3 times a week, but an orgasm is an orgasm. Being virgin doesn't cause any physical problems.

I wouldn't say there's zero chance for stds by not having ever had sex. STDs are a broad category, and many have other means of transmission. I've almost stepped on hypodermic needles, and I've had the occasional wart or two spring up on a finger or toe (which is caused by one of many strands of HPV, and although it's rare, HPV that likes one type of skin can migrate to another region such as the genitals). The first wart on my finger showed up around age 4 or 5, and was most likely from touching something someone else with the virus touched.

Bad blood transfusion or simply being born with an STD from one's own mother is a possibility, too.