As the cluster of hantavirus cases grows, here's what we know and how investigators try to ascertain whether there was person-to-person spread, says this public health doctor. NEWCASTLE, Australia: The cruise ship cluster of hantavirus cases continues to grow. The World Health Organization reported that as of Thursday (May 7) there were eight cases, five of which confirmed by laboratory testing as hantavirus. Three passengers have died. Now some passengers are being medically evacuated from the