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SAN JOSE, Calif. (KGO) -- Four additional firefighters have tested positive for novel coronavirus, San Jose city officials say . This comes after the San Jose Fire Department said Thursday that 4 tested firefighters tested positive and at least 52 others were on leave for possible exposure. San Jose Asst. Fire Chief Reggie Williams said Thursday he doesn't know how the firefighters contracted coronavirus. At least one of the firefighters is now being treated at a hospital in the city in which he resides."Because our firefighters work in teams and they train together, and they eat together, and they sleep in the same areas, they are at risk for possible exposure," said Williams.A new case of COVID-19 has also been identified in a Transportation Security Officer at Mineta San Jose International airport. On Tuesday, TSA officials announced three of their workers tested positive of COVID-19 and they are being medically treated and quarantined at home.Union representatives say the TSA workers who tested positive for the virus worked at Terminal B.James Mudrock, president of AFGE Local 1230, the union representing airport security screeners in Northern California, said Wednesday at least 42 employees have been told to self-quarantine for differing amounts of days, based on their last known contact with one of the infected officers."I would hope that we would be able to keep everything open and maintain the passenger flow, but if it gets worse, there's no telling," said Mudrock. "Our officers are committed to what they do, that we are taking every precaution that we are able to, and we appreciate the traveling public also taking precautions."