South African Experts Identify Hantavirus Outbreak on Cruise Ship

When South African infectious disease specialist Lucille Blumberg checked her email on the morning of May 1, while the country was celebrating the Labour Day holiday, an urgent message caught her attention. A UK-based colleague, who monitors diseases in remote British overseas territories in the South Atlantic Ocean, had written about a passenger from a cruise ship, sailing thousands of miles away in the Atlantic, who had been evacuated and admitted to a Johannesburg hospital with suspected pneumonia. Others aboard the vessel were also sick.

Blumberg and other experts at South Africa's National Institute for Communicable Diseases were suddenly thrown into the race to identify the cause of an outbreak aboard the Dutch cruise ship MV Hondius. Despite a holiday, "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 her colleagues had to rule out a host of other possible infections before narrowing down to the original cause.

First, they thought it might be Legionella, a bacterium that causes a serious form of pneumonia, bird flu. "Legionella is well described in outbreaks in hotels and on cruise ships, and influenza certainly is." Tests on all those were negative. The experts also ran an extensive panel of tests for other respiratory diseases. Also, all negative.

The team then began looking more closely at bird watchers and had reportedly been to parts of South America where there were birds, but also rodents. That pushed the South African disease experts toward another theory: the rare, rodent-borne hantavirus infection, which is found in parts of South America. "It's a well-described, not common, virus in Chile and Argentina," Blumberg said.

There was also timely help -- hantavirus experts from South America and the United States, facilitated by the WHO, the UN health agency, were a Zoom call away. "That was quite extraordinary," she said.

By then, it was Saturday morning. Blumberg called the head of the only laboratory in South Africa that can test for hantavirus. "I said, we want to do hanta, and she said, 'yeah, I'm coming.'"

The tests, carried out on the sick man's blood samples, came back positive for hantavirus that afternoon. And the team did a second set of tests to confirm it.