The headlines have been eerily familiar.
Passengers stuck on a cruise ship due to a mysterious viral outbreak that has led to the deaths of three people. A country refusing to let them dock. More potential cases popping up among passengers who disembarked before they knew what fellow passengers were carrying.
For some, the reports might feel like déjà vu, recalling early 2020 and the start of the COVID-19 pandemic. But the World Health Organization (WHO) and infectious disease specialists from around the globe have deemed the threat of a wider outbreak to be quite low.
“This is not COVID. This is not influenza,” Dr. Maria Van Kerkhove, who heads the WHO’s epidemic and pandemic preparedness, told a news conference in Geneva on Thursday.
Dr. William Schaffner, an infectious-disease professor at Vanderbilt University, said that unlike with COVID, human-to-human spread of hantavirus is quite rare and requires extremely close contact.
“I think this is going to be a well-confined circumstance to the cruise ship’s passengers, and there may be a little spread beyond that,” he said. “But I don’t think it will be another pandemic.”
Still, he cautioned that “this is an evolving circumstance, and as more information comes in, we may change what we say.”
What is hantavirus?
According to the WHO, “hantaviruses are a group of viruses carried by rodents.” The strains present in the Americas can cause hantavirus cardiopulmonary syndrome (HCPS), a severe respiratory illness with a fatality rate of up to 50 percent.
The Andes strain is the only variety to have documented human-to-human contact, and that is usually limited to people who have had very close contact with sick persons, such as people living in the same house.
While hantaviruses are fairly rare, the Associated Press reports that cases have been rising along with temperatures in Argentina. Since June of last year, the Argentine Health Ministry reported 101 hantavirus infections, roughly double the number from the same period a year prior.
What we know so far about the current outbreak
Eight cases of hantavirus have been reported among people traveling aboard the Dutch expedition ship MV Hondius. Operated by Oceanwide Expeditions, it set sail April 6 from Ushuaia, Argentina, before traveling to Antarctica and then to Africa, according to the WHO. Five of the eight cases, including three deaths, have been confirmed as the Andes strain, which is found only in South America. All but one person became ill while on the boat. That passenger had disembarked before the outbreak was known and is now hospitalized in Zurich, according to the WHO.
Additionally, the New York Times reports that another person is being tested for the virus: a KLM flight attendant who was on a flight that a sick passenger boarded in Johannesburg before being deemed too ill to fly.
How did it get on the ship?
How hantavirus made its way onto the expedition vessel is the question investigators are trying to definitively answer. The couple believed to have contracted the virus first had spent a few weeks on a bird-watching tour in Argentina before boarding the ship, where health officials say they could have encountered rat droppings, urine, or saliva.
The other possibility is that a rodent got onto the ship and particles from its droppings spread through the ship’s ventilation system, said David Freedman, an infectious-disease professor at the University of Alabama at Birmingham. But rodents on ships are rare, one cruise expert told USA Today, and the ship’s operator, Oceanwide Expeditions, told the WHO no rodents were found on board.
How many people are still on board the MV Hondius ship, and for how long?
According to Oceanwide Expeditions, about 90 passengers are on the ship, which was allowed to make a medical evacuation but denied docking earlier this week in Cape Verde, an island country off the west coast of Africa. The boat is on its way to the Canary Islands, where Spanish officials have committed to working with the WHO to safely disembark the passengers.
Has it spread beyond the ship?
Other than the passenger in Zurich and the flight attendant who’s being tested, no other cases off the ship have been reported as of Thursday. But more than two dozen passengers from at least 12 countries, including the United States, left the ship on April 24 without contact tracing and boarded flights to many corners of the globe, including California, Arizona, and Georgia. Health officials in those states and around the world say they are monitoring those passengers and developing information about who they have been in contact with.
How long before we know if the outbreak will continue to spread or if it’s over?
The incubation period for hantavirus is anywhere from one to six weeks, so infectious disease experts say we may see occasional instances of secondary cases—such as doctors who are treating the patients or others who may have had close contact with an infected passenger from the ship—in the months ahead.
“I think it’s going to burn out quickly,” said Freedman, noting that people shouldn’t panic if there are sporadic cases in the coming weeks.
