Starting next week, all travelers arriving in Puerto Rico must take and present a negative COVID-19 test within 72 hours — or face a $300 fine.The move is part of the governor's mandate to establish stricter measures to slow the spread of the coronavirus.The fine can be avoided if the traveler uploads a negative test result to a government online portal within 48 hours after arriving to the island.However, the visitor should still quarantine until authorities determine that the requirements have been met.Those who test positive must remain isolated for an amount of time that's still to be determined by the health department.The new rule goes into effect April 28.