SYDNEY, Dec 9 (Reuters) - Australia Deputy Prime Minister Barnaby Joyce has tested positive for COVID-19 in Washington, DC while on an official visit, his office said in a statement on Thursday. The remaining members of his delegation have tested negative and Joyce will remain in isolation until further advice, the statement said. Joyce had been experiencing mild symptoms and chose to get tested for COVID-19. He is the highest-ranking Australian leader to contract the virus since the pandemic began. Joyce reached the United States on Tuesday after a visit to Britain, where he met senior government officials.