What to know about hantavirus

Hantavirus refers to a family of viruses carried by rodents. It's often transmitted to humans by inhaling particles of dried deer mouse droppings or urine. Only one type of hantavirus has been known to spread person-to-person, which is called the Andes virus, according to CDC.

Since CDC first started tracking hantavirus in 1993, there have been 890 total cases as of the end of 2023.

At first, hantavirus causes flu-like symptoms, including fever, chills, body aches, and headaches, but as it progresses, respiratory symptoms develop and patients can experience shortness of breath followed by lung or heart failure.

Currently, there are no targeted treatments or widely available vaccines for hantaviruses , though a handful of scientific teams around the world have been working on developing both.

"I do think there are things that are sitting there on the bench that could be quickly developed," said Ronald Nahass, president of the Infectious Diseases Society of America. "But nothing is ready."

The latest outbreak occurred on the MV Hondius, a cruise ship carrying around 150 passengers that left Ushuaia in Argentina last month for the Canary Islands, making several stops along the way.

In total, six people were infected with the virus on the ship. Of those infected, three have died and one is in intensive care in South Africa.

In a statement, the operator of the ship, Oceanwide Expeditions, said it's closely monitoring the situation "and is deploying all available resources to ensure appropriate medical care and support for passengers and crew."

The World Health Organization (WHO) confirmed that the hantavirus involved in the outbreak is the Andes virus.

One of the patients, a 70-year-old male, became sick and was experiencing a fever, headache, abdominal pain, and diarrhea, according to Foster Mohale, a spokesperson for the National Department of Health in South Africa. The passenger died on arrival to St. Helena Island.

"I don't know of any other cases reported on a cruise ship before," said Emily Abdoler, a doctor and clinical associate professor of medicine at the University of Michigan Medical School.

James Lawler, of the University of Nebraska Medical Center's Global Center for Health Security, said that it's possible the cruise ship guests "all could have been infected at one event, before the ship got underway, and these are all just cases from a single point source," which is why an investigation is essential. However, Lawler added, "if there are multiple generations of cases, waves of cases, then that makes it more likely that there was human-to-human transmission."

Experts say the risk to the public is low

Many passengers from the ship have already disembarked, including some Americans who are now back in the United States. Five U.S. states are monitoring passengers who disembarked the ship prior to any cases being confirmed onboard. So far, none of the individuals have exhibited any signs of illness.

On Saturday, CDC issued a Health Alert Network health advisory on hantavirus, urging healthcare providers to be aware of the potential for cases connected to the outbreak on the cruise ship.

On Sunday, HHS announced that a passenger returning to the U.S. from the cruise ship has tested positive for the virus while a second is showing mild symptoms. Both patients are traveling in the plane's biocontainment units "out of an abundance of caution," HHS said.

However, experts emphasized that the overall risk of hantavirus to the public is low.

"It's not the next pandemic," said Michael Osterholm, director of the University of Minnesota's Center for Infectious Diseases Research and Policy.

"This is one where everyone should just take a breath and know that we are going to bring this to resolution," he said. "With adequate respiratory protection, [they could] very well stop all transmission from this point forward."

Part of the reason for concern from the public could be the fact that hantaviruses aren't especially well known, said Florian Krammer, a virologist at Mount Sinai's Icahn School of Medicine and director of the Ignaz Semmelweis Institute at the Medical University of Vienna.

"Three days ago, nobody knew what a hantavirus was," he said. "I think that's part of it."

"This outbreak highlights the importance of simple public health measures to recognise new infections and reduce spread and severe illness/deaths," said Andrew Pollard, a professor of infection and immunity at the University of Oxford's Pandemic Sciences Institute. "It is also a reminder that there are many dangerous viruses out there and we remain at risk from them in sporadic outbreaks like this."