Is hantavirus the next COVID? Is the U.S. response on point? An outbreak update

He and his wife "had been bird watching — not normally considered a hazardous sport — at a landfill outside of Ushuaia, Argentina," said Dr. Jeanne Marrazzo, CEO of the Infectious Diseases Society of America at a press conference on Wednesday. She said it was possible the man was exposed to the virus at the landfill, although she emphasized that this theory has yet to be confirmed.

Humans usually contract hantavirus by breathing in virus particles from infected rodent urine, feces or saliva. The specific type of hantavirus that this man picked up, called the Andes virus, is the only type of hantavirus known to transmit human-to-human, says Dr. Emily Abdoler, a clinical associate professor of medicine at the University of Michigan.

Current evidence suggests this man then boarded the cruise while asymptomatic and developed symptoms a handful of days into the voyage, says Marrazzo. At that point he spread the virus to others, including his wife. Both husband and wife have died, as well as one other passenger, a German woman. The doctor on the boat is one of the eight patients and has been evacuated to Europe for treatment, she added.

What to know about symptoms, treatment and death rate

Hantavirus can cause an infection that starts with flu-like symptoms, including fatigue, fever, muscle aches and at times diarrhea and vomiting. In some patients it can progress to a severe, and sometimes deadly, respiratory infection.

There is no vaccine or specific treatment for hantavirus. WHO officials urge people who might be infected to seek care from a trained professional quickly because medical care — such as being put on a ventilator — can help.

The death rate, according to the CDC, can be between 30 and 40%, although Marrazzo said this is likely an overestimate.

"While those are very scary numbers we often don't know what the denominator of people infected is, because mild cases might be missed."

There is no over-the-counter test for hantavirus. So it's often only the sick people who show up at the doctor and get tested. That means the mortality rate might appear higher than it actually is.

What to know about how the virus spreads

There are not many cases of human-to-human transmission, so medical professionals and scientists are still learning more about how the virus jumps from one person to the next. However, they believe that hantavirus spreads primarily between people who are showing symptoms and in close contact.

"Transmission between people has been associated with close and prolonged contact, particularly among household members, intimate partners and people providing medical care," says WHO Director-General Tedros Adhanom Ghebreyesus.

Many experts are looking back at a 2018-2019 outbreak in Argentina for clues. In that outbreak, the virus spread among birthday party guests who were seated near each other, a 2020 study published in the New England Journal of Medicine explains. Then, the virus spread further at the wake of the first person who fell ill and died. His wife, who had contracted the virus, attended with a fever.

Dr. Abraar Karan, an infectious disease faculty and physician at Stanford University, says the Argentinian outbreak shows this virus can spread in "very close, crowded settings." However, even that outbreak was relatively contained with only 34 confirmed infections.

He says the challenge is that the early flu-like symptoms are generic, so it can be hard to know to take precautions. But, on the flip side, he says, when people deteriorate it tends to happen quickly — in a matter of days — leading to isolation or death, "so the window of when you're going to potentially expose other people while you're contagious is short."

The difference between this outbreak and COVID-19

First, unlike COVID-19, which is a new virus, hantaviruses have been known and studied for decades.

"These viruses were first identified during the Korean War," says Dr. Carlos del Rio, a professor of global health and epidemiology at Emory University's Rollins School of Public Health. He explains that it was named for the Hantan River, just south of the demilitarized zone between North and South Korea.

Second, hantavirus does not spread as easily as COVID or flu.

Third, COVID and flu mutate very quickly, with new strains popping up often. As the virus reshapes itself, it can be challenging to contain.

Marrazzo says analysis of the Argentinian outbreak shows the virus did not mutate rapidly. "That's very different than something like the respiratory viruses that we worry about so much: COVID, influenza," she says.

What happens to all the other passengers

More than 100 people are still on the cruise ship but they are not showing any symptoms. "All passengers have been asked to stay in their cabins. The cabins are being disinfected, and anyone who shows symptoms will be isolated immediately," says the WHO's Van Kerkhove.

The boat is currently off the coast of Africa — traveling from Cape Verde to the Canary Islands, where the remaining passengers will disembark. Van Kerkhove adds that plans are being made to get them off the boat in the Canary Islands and medically assessed. "There is a step-by-step plan in development with many different experts to be able to say, once that ship docks, what will happen," she says.

However, more than two dozen passengers previously disembarked on the island of Saint Helena in the middle of the South Atlantic Ocean on April 24. From there they dispersed to a dozen countries, including to Turkey, Singapore, New Zealand and the United States.

National health authorities are now working to track them down and will make their own decisions about monitoring and even quarantining. The virus can stay in the body for one to six weeks before symptoms arise, so these people will be monitoring their health for a little while.

This group of disembarked passengers includes two Texas residents. Public health workers in Texas reached out to them; they have reported no symptoms and no contact with the sick passengers. "They have agreed to monitor themselves for symptoms with daily temperature checks and contact public health officials at any sign of a possible illness," said a press release Thursday from the Texas Department of State Health Services.

Assessing the U.S. response

U.S. public health experts are raising concern about the lack of a robust public U.S. response from the country's leading health agencies.

"I would envision that by now — many, many days ago — we would have seen a team from CDC [U.S. Centers for Disease Control and Prevention] deployed to the area, and we haven't seen that," says Emory's del Rio. He added that he would have also expected press conferences and health alerts to inform the public and medical community about what is happening and how best to respond.

CDC did send out a statement on Wednesday night saying it was "closely monitoring the situation" and that "the Department of State is leading a coordinated, whole-of-government response including direct contact with passengers, diplomatic coordination, and engagement with domestic and international health authorities." However, it did not provide details or guidance.

CDC did not respond to NPR's requests for comment on the concerns expressed about the lack of a U.S. response to the outbreak.