The suspected hantavirus outbreak on the MV Hondius cruise ship, which has killed three people and sickened at least seven others, has two likely causes — and both are bad news for the 150 passengers on board, experts said. The more likely scenario would be passengers contracting the virus from the feces, urine or saliva of infected rats or mice. That’s the usual transmission vector, according to physician Zaid Fadul, a former Air Force flight surgeon — although the World Health Organization insisted Tuesday that no rodents have been found on the stranded liner. But there’s one strain of the...