JOHANNESBURG: When South African infectious disease expert Lucille Blumberg checked her email on the morning of May 1, as the country was celebrating the Labor Day holiday, an urgent message caught her attention.A UK-based affiliate, which monitors diseases in remote British overseas territories in the South Atlantic Ocean, wrote about a passenger on a cruise ship sailing thousands of miles across the Atlantic who was admitted to a Johannesburg hospital with suspected pneumonia. Other people on board the ship were also ill. Blumberg and other experts at South Africa’s National Institute for Communicable Diseases were suddenly thrown into a race to identify the cause of the outbreak on the Dutch cruise ship MV Hondius. Despite the holidays, “it got busy,” she says. Within 24 hours, they had determined that the man’s illness was caused by hantavirus, a rare rodent-borne virus. But first, Blumberg and his colleagues had to rule out several other possible infections before narrowing down the root cause. At first, they thought it might be Legionella, a bacterium that causes pneumonia, a severe form of bird flu. “Legionella has been well described in outbreaks in hotels and on cruise ships, and influenza certainly has.” The tests on all of them were negative. The experts also ran a comprehensive panel of tests for other respiratory diseases. Also, all negative.The team then began tracking bird watchers more closely and reportedly went to parts of South America where there were birds, but also rodents. This pushed South African disease experts toward another theory: a rare, rodent-borne hantavirus infection, which is found in parts of South America. “In Chile and Argentina this is a well-characterized virus, not common,” Blumberg said. Timely help also arrived – hantavirus experts from South America and the United States, assisted by WHO, the United Nations health agency, were a Zoom call away. “That was quite extraordinary,” she said.By then it was Saturday morning. Blumberg was said to head South Africa’s only laboratory that can test for hantavirus. “I said, we want to do hantavirus, and she said, ‘Yes, I’m coming.'” Tests conducted on blood samples from the sick man came back positive for hantavirus that afternoon. And the team conducted a second set of tests to confirm this.