Is there a risk of contracting hep b or c from a piece of watermelon contaminated with infectious blood? i think there was a blood streak on my watermelon yesterday from someone of unknown status. very scared. i know its not an hiv risk?

Depends on what you call a lot of blood. Anything that can be blood borne and transmitted by oral route could be transmitted. I advise not eating bloody watermelon.

HIV, Hepatitis B and C cannot be transmitted through above mentioned mechanism. Hand hygiene rules still apply as to risk for transmission for other bacteria including hepatitis A. Check cdc.gov in order to clarify.