Hantavirus outbreak isn’t another Covid pandemic – but experts say it’s testing U.S. readiness

A cruise ship outbreak of hantavirus has rattled the public and reignited fears of another global health scare as passengers disperse across multiple countries, including the U.S. 

The World Health Organization reported 11 cases linked to the outbreak as of Tuesday, nine of which it confirmed, including three deaths. No Americans have tested positive as of Wednesday.

Other passengers are being monitored in specialized medical units, including 18 in the U.S. across Nebraska and Atlanta. A handful of people not connected to the cruise are also being evaluated for possible exposure across several states. Treatments specifically for hantavirus are still years away: Shares of Moderna rallied around 12% on Friday after it confirmed it was conducting early research on a potential vaccine to protect against hantavirus.

But as the number of exposed individuals and public concern grow, health experts aim to tamp down fears of another pandemic. Their message: This is not Covid-19 all over again. 

Unlike Covid, measles or the flu, the specific Andes strain of hantavirus in the outbreak does not spread easily between people, making the risk of widespread spillover to the public low. More cases could emerge in the coming weeks because hantavirus has a long incubation period, experts said.

Still, “we are not expecting a large number of infections and they will likely remain limited to passengers who were exposed aboard the ship, especially now that we have containment measures in place,” Dr. Nicole Iovine, chief hospital epidemiologist and an infectious disease physician at the University of Florida, said in an interview. 

But for other experts, the outbreak is raising broader concerns about how equipped the U.S. is to respond to future infectious disease threats, particularly after major cuts to the Centers for Disease Control and Prevention and the Trump administration’s move to withdraw from the WHO last year.

While experts say the CDC appears to have the hantavirus outbreak under control, some warn that the situation exposed cracks in the nation’s public health infrastructure that could carry greater consequences in the face of a more contagious pathogen.

“I’m not expecting any significant risk to the American public. But if this is a stress test, we failed this,” said Lawrence Gostin, professor of public health law at Georgetown University. “Just imagine if this were actually a highly transmissible agent.”

In the meantime, Modern

Here’s what to know about where the hantavirus outbreak stands, and what it says about the U.S. ability to contain infectious diseases.

Hantavirus is primarily transmitted to humans through contact with infected wild rodents, especially through inhaling airborne particles from their urine, droppings, or saliva. Cases of hantavirus disease are rare in the U.S.: From 1993 to 2023, 890 cases were reported, most of them in Western states, CDC data shows.

The Andes strain of the virus seen in the outbreak – and found in South America – is the only hantavirus that can spread from human to human. Still, there are few cases of human-to-human transmission, so the medical community is drawing clues from previous outbreaks. 

The Andes strain typically spreads through “close and usually prolonged contact” with an infected individual showing symptoms, said Dr. Kari Debbink of the Johns Hopkins Bloomberg School of Public Health. 

Debbink said that’s unlike Covid, which “spread pretty efficiently without a very long exposure.” Hantavirus is not considered airborne because it does not linger in the air to infect others in the same way that respiratory viruses like Covid, the flu and measles do.

But cruise ships like the MV Hondius are considered ideal environments for disease transmission because they bring together a wide variety of people and stick them in close quarters for days or even weeks. 

“Cruise ships are one of the greatest threats to public health. They are floating petri dishes isolated in the water,” said Dr. Tyler Evans, CEO of public health organization Wellness Equity Alliance and the former chief medical officer for New York City’s Covid response. 

WHO investigators believe the outbreak stemmed from a Dutch couple on board the MV Hondius cruise ship who later died from their infections. 

Before boarding, the couple had gone on a bird-watching trip through Argentina, Chile and Uruguay, Dr. Tedros Adhanom Ghebreyesus, director-general of the WHO, said at a May 7 briefing. He said the couple’s bird-watching trip included visits to sites where “the species of rat that’s known to carry hantavirus was present,” he said. 

Hantavirus has an incubation period of one-to-six weeks after exposure, which means that more cases will likely crop up, said Debbink. But the people who made contact with infected individuals are being monitored for symptoms in specialized facilities, so “this should be contained rather quickly,” she added. 

Trump cut roughly 10% of the CDC’s workforce in early 2025, leaving fewer epidemiologists and scientific staff to do boots-on-the-ground work or coordinate responses across governments. There is currently no permanent CDC director or U.S. surgeon general, both positions that play a critical role in responding to disease threats.

“They don’t have the right leadership at the CDC,” said Evans. “They’re sort of on a ship without a captain at the helm, so they’re scrambling a bit and doing the best they can. There are serious concerns about it.”

Gostin said the CDC lagged behind the WHO and European health authorities, saying the agency escalated its actions “a week after the international community started mobilizing around a potential global health crisis.” The outbreak was first reported on May 2 to the WHO, which quickly took a number of actions, including deploying an expert on board the ship.

The CDC issued its first public statement about the outbreak on May 6 and its first official health alert to U.S. doctors on May 8, which warned of the possibility of imported cases. The agency confirmed it had deployed a team on May 7 to Spain’s Canary Islands, where the ship arrived two days later, and a second group to Nebraska as part of a plan to evacuate U.S. passengers from the ship. 

While the CDC is now working with the WHO, experts say the Trump administration’s decision to sever ties with the international health body is detrimental to the U.S.’s ability to respond to future outbreaks. For example, the U.S. no longer has direct, automatic access to real-time information from member states of the WHO about emerging health threats. 

Neil Maniar, a public health professor at Northeastern University, said the response to hantavirus stands in stark contrast to 2020, when the CDC worked closely with international partners during Covid.

“That is what is needed to effectively respond to these types of outbreaks, and that is where the system has really broken down,” Maniar said. 

“We need to restore our country’s expertise and resources to respond because there are going to be future outbreaks,” he added. “It should raise significant alarm bells for everyone in terms of our readiness and ability to keep this country safe.”