This is a developing story and will be updated as new information is released.
One confirmed and five suspected cases of hantavirus infection have struck passengers of a cruise ship in the Atlantic Ocean.
What are hantaviruses?
Hantaviruses are a family of viruses typically carried and spread by rodents. People can catch the germs if they are exposed to the urine, droppings or saliva of infected animals, or rarely, if an infected animal bites them. One type of hantavirus, called the Andes virus, is capable of spreading from an infected person to other people, but such cases of human-to-human transmission have been rare. The specific type of hantavirus involved in the cruise ship cases has not been disclosed.
Hantaviruses can cause two types of serious infection: hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). The former infection can take up to eight weeks to develop after exposure to the virus; it starts with fever, chills and fatigue and progresses to potentially deadly organ dysfunction and respiratory issues. The latter infection takes about two to four weeks to set in and causes fever, headache, gastrointestinal issues, kidney dysfunction and, sometimes, internal bleeding.
HPS is deadlier than HFRS, with a fatality rate of 38% in patients who develop respiratory symptoms of the disease. The fatality rate of HFRS varies depending on the specific hantavirus a person is infected with, with fatality rates ranging from 1% to 15%.
Treatments for hantavirus disease aim to manage a patient’s symptoms; there is no cure for the infections.
What happened on the cruise?
So far, only one of the illnesses connected to the cruise has been confirmed to be a hantavirus infection, according to the cruise’s operator, Oceanwide Expeditions. The company, which offers expedition-style voyages to the polar regions and sub-Antarctic, detailed the situation in statements released May 3 and May 4.
The affected vessel is the MV Hondius, which departed from Ushuaia in Argentina about three weeks ago, The New York Times reported. It stopped in mainland Antarctica, the Falkland Islands, South Georgia, Nightingale Island, Tristan, St. Helena, Ascension Island and Cape Verde, and the ship currently remains off the coast of Cape Verde.
On April 11, a passenger died on board, and his cause of death could not immediately be determined. On April 24, that deceased passenger and his surviving wife, both Dutch nationals, were dropped off on St. Helena to await repatriation to the Netherlands. Three days later, Oceanwide Expeditions learned that the wife had also fallen ill and later died on her way back to the Netherlands. Neither of these illnesses have been confirmed to be hantavirus infections, the company clarified.
Meanwhile, on April 27, another passenger aboard the MV Hondius got sick and was evacuated to South Africa for treatment. The passenger, a British national, remains in intensive care in Johannesburg and is in “critical but stable condition.” Laboratory tests have confirmed that a hantavirus infected this patient, Oceanwide Expeditions said.
Another passenger died aboard the vessel on May 2, and his cause of death has not been determined. There are now two crewmembers with respiratory symptoms — one with mild symptoms and one with severe symptoms. These three new cases of illness have not yet been confirmed to be hantavirus disease.
There are 149 people on board the vessel, and local health authorities have visited the MV Hondius to assess the situation. Oceanwide Expeditions is collaborating with local and international authorities, including the WHO, which on May 4 announced that the two sick individuals on board will be evacuated to the Netherlands for medical care.
“Detailed investigations are ongoing, including further laboratory testing, and epidemiological investigations,” the WHO statement said. “Medical care and support are being provided to passengers and crew. Sequencing of the virus is also ongoing.”
In the May 4 statement, Maria Van Kerkhove, the WHO’s interim director of epidemic and pandemic preparedness and prevention, said, “Based on current information and what we know about the virus from previous outbreaks, the overall risk to the public is low.”
Is human-to-human transmission to blame?
To date, the Andes virus, found in Chile and Argentina, is the only hantavirus with strong evidence of human-to-human transmission. “For other hantaviruses, transmission is believed to occur almost exclusively from rodents to humans,” Luis Escobar, an assistant professor in Virginia Tech’s Department of Fish and Wildlife Conservation, told Live Science in an email.
Escobar’s lab researches the biogeography, ecology and evolution of infectious diseases, including hantaviruses. He noted that scientists don’t yet understand which biological features of the Andes virus make it capable of spreading between people.
It’s been difficult to pin down exactly how infectious the virus is to people, in part because public health authorities in Chile and Argentina have been quick to act in instances when human-to-human spread was suspected. Measures like contact tracing, isolation and monitoring have limited the virus’s spread, meaning there’s little data regarding its transmission between people.
“While it cannot be completely excluded that other hantaviruses [in addition to the Andes virus] might have some capacity for person‑to‑person spread, there is currently no convincing evidence that this happens,” he told Live Science. “But research has been limited.”
Current evidence does suggest that different flavors of hantavirus have distinct traits. For example, hantaviruses in North America and South America can infect a greater variety of rodent species than hantaviruses in Europe and Asia can. Although this flexibility doesn’t necessarily make the viruses in the Americas more likely to infect people, it does suggest “a greater tendency to cross species boundaries,” Escobar said. These differences among hantaviruses are an active area of study.
The WHO and other health authorities are still investigating the source of the cruise ship infections and whether human-to-human spread might be at play. If an Andes virus from South America is to blame, human-to-human spread wouldn’t be a total surprise. However, if a different hantavirus is the culprit, that could be significant.
“I would be surprised if authorities were to find some evidence of human‑to‑human transmission caused by a hantavirus other than Andes virus,” Escobar said. “Such a finding would fundamentally change our current understanding of hantavirus biology and would signal a much greater epidemic and pandemic risk than has ever been documented for this group of viruses.”
Editor’s note: This article was updated at 3:35 p.m. to add comments from Luis Escobar and an update from the WHO.
This article is for informational purposes only and is not meant to offer medical advice.
