A321 Captain reported a fumes event during pre-flight at gate prior to passenger boarding. The Captain submitted an AML discrepancy after flight crew deplaned.

Narrative

Upon receiving aircraft with the APU left running at gate for flight in ZZZ Flight Attendant NAME immediately noticed a pungent musty/wet sock odor around row 11. As we discussed the smell it continued to get stronger. I called maintenance and made a notation in the aircraft maintenance log. Gate agent noticed the smell when he came down to the aircraft as well as the maintenance personnel. The odor continued to get stronger as time passed. We were not on the aircraft for more than 10-15 minutes. Passengers never boarded the aircraft. Approximately 20-30 minutes after deplaning; all crew members had brief symptoms. Three of us had very mild headache; one had a mild sore throat; one had slight dizziness. All symptoms lasted about 10 minutes. I queried all crew member if medical attention was required; all confirmed they were OK to continue to ZZZ1. No medical attention was required for flight crew. The prompt identification and action of Flight Attendant [name] played a significant role in identifying a health problem for anybody boarding the aircraft.