You’re probably safe from the Hantavirus outbreak, but here’s what you absolutely must not do, experts say

The deaths of three passengers aboard the expedition cruise ship MV Hondius have triggered an international scramble to trace passengers and crew exposed to the rare Andes strain of hantavirus. The outbreak has reignited public fear about a virus most Americans associate with rural rodent exposure, and raised an uncomfortable question about whether human-to-human spread could become more common.

Two scientists working on opposite ends of the hantavirus problem—Dr. Scott Pegan, a virologist at the UC Riverside School of Medicine, and Dr. Marieke Rosenbaum, a veterinary public health expert at Tufts University’s Cummings School of Veterinary Medicine—both say the same thing: don’t panic, but take this seriously.

A self-contained environment aboard the cruise ship

For most of its known history, hantavirus has been a disease of close rodent contact: a dusty barn, a mouse-infested cabin, a grain shed. The Andes strain circulating through MV Hondius is unusual because it can spread, it seems, between people. But Pegan said the conditions on the ship were extraordinary.

“It’s a hypothesis that the virus builds up a higher titer in the saliva,” said Pegan of the blood test that measures the concentration of specific antibodies. He compared it to aspects of the earl...