90-Second Read: Hantavirus questions grow in the wake of a cruise ship outbreak

As public health officials around the world monitor dozens of former passengers and crewmembers of the MV Hondius for signs of Hantavirus infection, scientists are hoping to learn more about the mysterious and sometimes deadly virus that caused the outbreak. So far, evidence suggests the shipboard outbreak happened when one or two people were infected ashore and then passed the Hantavirus to others on board. Argentinian authorities dispute that the outbreak started at the landfill, pointing out that the rodents don't live in the Tierra del Fuego region of southern Argentina where the Dutch couple joined the cruise and that region has never had a human case of Hantavirus. Scientists still don't know why Andes Hantavirus is the only one shown to spread from person to person.

But in Chile and Argentina, researchers have previously documented cases in which people were infected with Andes Hantavirus by other people at birthday parties and wakes, in hospitals, on car trips and within households. Close contacts may also be those who spend long periods of time together or health care workers who take care of Hantavirus-infected patients. Hantavirus pulmonary syndrome outbreak in Argentina: Molecular evidence for person-to-person transmission of Andes virus. Many different species and variants of Hantavirus have been discovered.

As of May 13, the outbreak had sickened at least 11 people, killing three. Scientists are still trying to decipher what makes the Andes virus different from other Hantaviruses. Those are people who were on the Hondius when the first case died but disembarked before anyone realized Hantavirus was aboard. One reason that the Andes virus may spread among people is that it grows to higher levels in humans than other types of Hantaviruses do.

If there's nothing special about Andes virus's genetic makeup, that might mean other Hantaviruses are capable of spreading among humans given the opportunity. Still, many rodent species carry Hantaviruses that have unknown capabilities, Palacios says. Andes, like other Hantaviruses, also keeps immune cells called T cells from attacking the virus, Klingström says.