Royal Caribbean Group and Carnival Corp will push ahead with a return to cruises this summer despite two guests onboard a test run for Royal Caribbean’s Celebrity Millennium ship testing positive for COVID-19. A year after several cruise ships were host to major coronavirus outbreaks, cruise lines have been striving to get business going. Shares in Royal Caribbean, Carnival Corp and Norwegian Cruise Line Holdings Ltd, which all booked massive losses last year as restrictions brought the industry to a standstill, fell between 1 percent and 2 percent in response to the positive tests. Royal Caribbean declined to give more details on the guests who had tested positive or the circumstances of their infection, when asked by Reuters on Friday. Celebrity Cruises later said it was paying to fly both guests home privately on Saturday and planning to disembark the remaining passengers on time after being tested. The Celebrity Millennium …