What Marylanders need to know about hantavirus

Three people aboard a Dutch-flagged cruise ship have died and at least eight have been infected since April 11 from a relatively rare infection from hantavirus that normally doesn’t spread easily among people.

Close to 150 passengers remain aboard the ship headed to Spain’s Canary Islands, where they are expected to disembark if they show no symptoms of the virus.

Others have already left the ship, worrying global public health officials. About 30 passengers, including six Americans, got off in the British territory of St. Helena after the first death but before hantavirus was confirmed.

Marylanders likely haven’t forgotten the coronavirus pandemic and want to know if any passengers are headed back to neighboring states and what threat they pose.

So far health officials say they don’t expect mass spread based on the history of hantavirus, but here’s what they are concerned about.

What is hantavirus, and how common is it?

Hantaviruses are a potentially dangerous family of viruses that are passed to humans through infected rodents’ droppings. The risk of severe illness and death is dependent on the strain of the virus, according to the World Health Organization.

The most common strain in the Americas is called Andes — and it is the type linked to the cruise ship. It causes hantavirus pulmonary syndrome, and it’s especially dangerous. That can lead the lungs to fill with fluid and make breathing difficult. It has a high mortality rate of up to 50%.

European hantaviruses more typically cause hemorrhagic fever and renal syndrome, often damaging the kidneys and cardiovascular system.

There are 10,000 to 100,000 hantavirus cases annually, mostly in Europe and Asia. The federal Centers for Disease Control and Prevention reports one to two dozen cases around the nation annually and a total of 890 cases since 1993.

Since 2015, the Maryland Department of Health has reported one hantavirus infection in 2019 and two cases of hantavirus pulmonary syndrome in 2019 and in 2024.

“To date, the Maryland Department of Health has not been notified of any positive cases of hantavirus in Maryland related to passengers on the MV Hondius cruise ship,” said Amanda Hils, a department spokeswoman. “The Maryland Department of Health will continue to monitor the situation and take appropriate action if the department is notified of a positive case.”

What are symptoms, and how is an infection treated?

There’s no specific treatment or cure, said Dr. Kirsten Lyke, an infectious disease expert in the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine in Baltimore.

Early medical care for symptoms can improve chances of survival, she said. Providers will monitor for respiratory, cardiac and kidney complications once they know it’s hantavirus.

Early diagnosis, however, can be difficult because the virus can present with vague, flu-like symptoms. Confirmation is made through a blood test at a state or federal lab.

Three passengers have been taken to hospitals from the cruise ship for supportive treatment or monitoring, the cruise operator has reported.

Where are the passengers who have left the ship early?

At least one Swiss passenger has also received care, the ship operator said. The rest have returned home, including to the United States.

Officials in Virginia, Georgia, Arizona and California are in touch with the passengers and looking to trace their steps and monitor for new infections, according to news reports.

It’s not clear if passengers still on the ship will be monitored in port for a time or allowed to return immediately to their homes.

Lyke said, if they do, they should be instructed to wear masks and keep as much distance from others as they can. The incubation period can last up to eight weeks.

Should we be concerned about another pandemic?

Many people likely recall a British-flagged cruise ship that reported a strange infection that ultimately sickened 700 and killed nine of 3,700 passengers. Two years later, more than 1.1 million Americans had died from COVID-19, caused by a novel coronavirus.

Lyke and others insist this virus is not that.

This isn’t a new strain of hantavirus. And infections between humans are rare and usually associated with close and constant contact. It’s also not nearly as contagious as COVID.

Two of the deaths were a married couple likely infected in South America before they boarded the ship.

What’s next?

Lyke said keeping tabs on those who left the ship and those who will leave poses a challenge for public health officials.

Dr. Tedros Adhanom Ghebreyesus, WHO’s director-general, said on the social media site X that officials are monitoring the health of passengers and crew and working with the national health authorities of other countries to keep tabs on those who have disembarked.

He didn’t outline how, though he said WHO assessed the “public health risk as low.”

Ditto for the CDC, which said in a statement Wednesday it was monitoring the situation in the United States, and “the risk to the American public is extremely low.”

Lyke agreed there’s not likely to be a lot more cases and said this will be a good, and relatively safe, “test case” for the current public health infrastructure, which has come under strain during the Trump administration.

“This is getting a lot of attention because it’s a cruise ship and a mysterious virus and people are dying,” she said.

“This is exactly why we need to work together and have open sharing of science with the entire world,” she said. “We’re one ship, one plane, one traveler away from an outbreak.”