Origins of Cruise-Ship Hantavirus Outbreak Under Scrutiny

The lethal hantavirus native to South America is under scrutiny by medical researchers, who doubt that the cruise-ship cases in April originated from a landfill in Ushuaia, Argentina, as originally conjectured. For one thing, long-tailed pygmy rice rats, the species that carries highly contagious Andes hantavirus, were not trapped at the landfill. What has turned up could lengthen quarantine periods for those exposed, the journal Science reported on June 11.

The Dutch couple who first became ill aboard the cruise ship M/V Hondius had traveled through South America for four months. Their route included the landfill in Ushuaia, the town where they boarded the ship, but also an area along the Argentina and Chile border. Sequences of the virus from Hondius patients matched closely to infections in 2018 from Neuquén province, scientists at Argentina’s National Institute of Infectious Diseases determined. Across the border in Chile, a PhD student at the University of Development, Lissette Ulloa-Zepeda, and her fellow researchers published surveillance results in May from genetic sequencing of Andes hantavirus samples from 2013. They matched even more closely.

The likely location of the Hondius infections points to this border region as the Dutch couple had traveled there in early February. But a 60-day incubation period would be “unprecedentedly long” wrote Kai Kupferschmidt in the Science article. The quarantine period for Andes hantavirus, based on how long it takes for symptoms of illness to appear, is currently about 42 days.

Andes hantavirus is transmitted by the pygmy rice rats, much as North America’s Sin Nombre hantavirus is generally from deer mice. The fatal difference is that the South American variety can transmit from an infected human to another human directly. In the case of North America’s hantavirus, people become ill if they stir up mouse poop and breathe the airborne virus. However, the fatality rate in Sin Nombre is equally high: 30 to 40 percent.

Speculation that a rat got into the couple’s van as they crossed from Chile to Argentina was unconfirmed after searches of the vehicle turned up no rats or feces. Another guess was that the Dutch man was infected by another human during his travels with his wife. The two, who were retired ornithologists on a bird-watching tour, both became very ill and died on April 11 and April 26, respectively.

Among the more than 180 individuals aboard the Hondius, three people died of the severe respiratory disease caused by hantavirus pulmonary syndrome. Eight others, including the ship’s doctor and a guide, either became ill or tested positive. After floating off the West African coast for a week, the ship was finally allowed to disembark passengers and crew at the Canary Islands on May 11.

The passengers and crew were an international group, but for the Americans aboard, a 42-day quarantine was in store. One group that left the Hondius mid-cruise at St. Helena island all returned to their home states, where their quarantines ended on June 6. Eighteen who left the Hondius at the Canaries ended up at the National Quarantine Unit in Nebraska. As of June 17, 12 patients returned to their homes to complete the quarantine period, while six stayed at the NQU. All were symptom free, the Centers for Disease Control reported. California’s public health department reported that the five passengers known to be from the state are symptom-free.