Hantavirus doesn't linger, requires close contact: Officials

Health officials around the globe have taken major steps to prevent the spread of the hantavirus that spread throughout the MV Hondius, and an American doctor who was onboard noted how conditions on the cruise ship may helped the virus spread.

In the U.S., the boat's 18 American passengers have been put in quarantine in Nebraska with two in Atlanta while more than 40 people with exposure to the sick are being monitored to see if they develop the illness.

While health experts acknowledged that the scenario may seem similar to the beginning of the 2020 COVID-19 pandemic, they told ABC News that the current science behind the hantavirus does not show the same levels of transmission.

"Our current understanding is that person-to-person transmission of Andes virus is relatively rare and generally associated with prolonged close contact," says the current Centers for Disease Control and Prevention public health assessment. "There is also no documented evidence of presymptomatic transmission."

"In the vast majority of cases it happens when people breathe in mouse secretions," Dr. Emily Abdoler, a clinical associate professor of medicine at the University of Michigan, who specializes in infectious diseases, told ABC News.

"The Andes strain found in Chile and Argentina has the possibility of human-to-human transmission, but that's really more really close contact. It's not sharing the same household," she added. "It's more like sharing the same bed."

Dr. Stephen Kornfeld, an American oncologist who became the ship's de facto doctor after the Hondius' physician contracted the virus, initially received inconclusive results with samples taken from the ship but later tested negative.

Speaking to ABC News from his quarantine on Thursday in Omaha, he noted that conditions on the ship could have created a "complicated" situation for transmission while observing some social casual contact.

Speaking to ABC News from his quarantine on Thursday, Kornfeld noted that conditions on the ship -- including ventilation and the size of rooms -- could have created a "complicated" situation for transmission.

"If you do have casual contact, you're doing it repetitively," he said. "There were three rooms that we would gather in many times a day, often for an hour or an hour and a half, for lectures and discussions and meals. And I can just envision lots of frequent casual contacts, and perhaps over time that adds up to something more than just a single casual content."

Abdoler, who helped diagnose a case of hantavirus in Michigan in 2021 -- the type we have the U.S. that does not spread between people --said the benefit that medical professionals and agencies, such as the World Health Organization, have now is that the hantavirus has been researched for over 30 years. It is not a new virus.

While the data around the Andes strain believed to have been on the boat is still limited given the rare number of cases outside of South America, Abdoler said there does not appear to be any indication that the transmission methods have changed for the Andes strain.

ABC News medical contributor and epidemiologist Dr. John Brownstein concurred, saying that previous research suggests the hantavirus is a respiratory illness. That means germs can be coughed up, he noted, but it is not an aerosol-based virus.

"It's not like COVID or measles where it could linger in the air for some time," he said.

Brownstein added that the incubation period for the virus is long, and despite the lower risk for person-to-person transmission, it is critical that health officials stick to their policies to isolate and monitor anyone connected to the Hondius. Isolation can then be initiated if they become a positive case.

"Incubation can be anywhere from one to eight weeks," he noted.

During a news briefing Friday, WHO officials stressed that said there is no evidence so far that the virus has changed to become more transmissible or more severe.

Officials said transmission is believed to be based on several factors, including how infectious the patient is, the environment and whether protection and PPE was used.

On Friday, acting Centers for Disease Control and Prevention director Jay Bhattacharya told reporters no cases of hantavirus have been reported in the U.S.

There are now at least 10 cases that have been linked to the ship's outbreak. Two passengers died from the virus and a third death has been deemed probable by WHO.

Sixteen Hondius passengers, including Kornfeld, are currently in quarantine the University of Nebraska Medical Center and have not shown any symptoms as of early Friday.

Two other American passengers were flown to Atlanta for "assessment and care," according to officials.

The remainder of the passengers are in quarantine at home and are being monitored.

WHO warned more positive cases could still appear during quarantine because the virus' incubation period is long, but said that would not necessarily mean the outbreak is growing.

Abdoler noted that the fact that there have not been as many positive cases from the ship and their contacts shows that the data about the Andes transmission is holding up and there are no signs that the virus can spread as easily as other pathogens. He noted that he is glad that the risk is being taken seriously and that those that have been exposed are being monitored.

"My sense is that there is no really need to panic, but [WHO] is taking a very conservative approach to the outbreak and asking everyone to isolate during the intubation period," she said.

"I think it is good they are taking a conservative approach because there are unknowns, but I am not personally altering my personal practices of travel or how I go out," she added.

- ABC News' Dragana Jovanovic contributed to this report.