How far can the Hantavirus Outbreak Go?
By Molly Cavanaugh, May 2026
On April 1st, the MV Hondius cruise ship departed from Argentina and what followed seemed the start of a horror movie (1). 10 days after departure, the first passenger was dead. On April 26th the first passenger’s wife died in South Africa after 32 of the possibly infected passengers left the ship. It was not until May 2nd that the World Health Organization, WHO, was called. A third passenger died the same day. As of May 13th, there have been 11 cases and three deaths reported from the ship (2). 12 countries are quarantining and monitoring possible cases of Hanta virus, even though most of those in quarantine have tested negative (3). The US is scarred from Covid and is rightfully worried about a new pandemic, but this outbreak will not turn into a pandemic if we keep fighting it.
Hantavirus, while rare, is not new to the United States. Hantavirus even made the news in 2025 when Gene Hackman, a famous actor, and his wife were found dead, with his wife dying of hantavirus (4). From 1993-2023, there were 890 hantavirus cases occurring in 40 US states and 2 cases were even in D.C (5). Almost all hantavirus cases in the US took place West of the Mississippi river. This virus has a 20-40% death rate and there is no treatment (6). Symptoms are not easy to miss, often including a cough, fever, and either bleeding disorders and kidney failure or fluid accumulating in the lungs and shock. Hantavirus is a virus spread primarily by rodent droppings and anyone around rodents should use protection when. Hantavirus strains in the US do not spread from person to person. Only one type of hantavirus, called the Andes strain, can be spread by people. This is the strain of virus which infected MV Hondius cruise ship.
Viruses, as well as bacteria and fungi, have strains. Strains are variants on an overarching microbe. They have a slightly different genetic code which can result in different symptoms or death / infectivity rate. For example, the flu is different every year, but it is always the flu. There are certain strains of the flu with higher death rates like the 1918 flu (7). Hantavirus also have different strains that exist in different parts of the world. Viruses are often named after locations that they were found. In this case, Hantavirus was named for the Hantaan river in Korea and the Andes strain was found in the Andes Mountains in South America (8). While this strain can pass from person to person, fewer than 40 people have ever been recorded getting hantavirus from human to human transmission (9). In each of these cases, it was close contact like from doctor to patient or people at a party. This type of transmission was so rare that before this outbreak, scientists debated if it was even possible (10). So, why would this outbreak pass person to person more than in other outbreaks?
Cruise ships are notorious for outbreaks. In 2025, there were 24 outbreaks on cruise ships that traveled to foreign countries and had a stop in the US (11). There were 18 the year before that. These ships provide close contact and a semi-enclosed environment that allows bacteria and virus to infect far more people than on land (12). Cruise ships also have limited medical capabilities and tend to have older passengers who are at higher risk (13). These factors make it perfect for an epidemic because it gives the virus or bacteria every advantage. There is no longer a debate that hantavirus can spread person to person, but that does not mean that this outbreak will be a pandemic like Covid.
As the outbreak become obvious, it was vital to quarantine everyone from the ship, which meant tracking them and everyone they were in contact with. Such a quick quarantine is essential to stopping an outbreak. A huge problem which influenced Covid becoming a pandemic was how late the virus was noticed. While we will never know the exact date that Covid started in the US, we know that it was at least in December 2019, giving the disease a minimum of 2.5 months to run wild and quietly infect every corner of the US (14). This is not the case with the MV Hondius cruise ship. Everyone involved in the original outbreak on the ship has been located and quarantined within days. There were initial, bigger pandemic fears last week when a flight attendant with close contact to a hantavirus patient was hospitalized for possible Hantavirus symptoms (15). But she has since tested negative meaning that so far the infection has been contained to those on the boat.
In addition to the outbreak being quickly contained, the virus is also not very infectious and large outbreaks are rare (16). Hanta virus is considered to be far less infectious than other viruses. Hantavirus has thus far infected 7.3% of those who were on the cruise ship (2). In similar conditions, like a respiratory virus outbreak on a cruise ship, would be considered a low rate of infection. For example, a similar outbreak happened at the start of Covid in February of 2020. A ship with 2,666 passengers and 1,045 crew members ended with 9 deaths and over 20% of the passengers getting infected (17). Another outbreak, this one of the flu in 2000, caused 37% of passengers surveyed to develop flu symptoms (18). Hantavirus is not considered, as of now, to be a very infectious disease. A low infection rate will result in fewer person to person transmissions (19).
Another factor that will prevent a pandemic is the rate of mutations. Some viruses, like SARS-COV-2 (the virus which causes covid) mutate quickly. A virus mutation can make a virus more contagious, more deadly, and importantly it can cause treatments and vaccines to not work as well (20). If a virus mutates a lot, it can cause different symptoms, making it a new strain. This was seen in the case of covid. Various strains of covid appeared, which resulted in the need for more vaccines because the part of the virus we were targeting was changing to avoid our vaccines. So far, hantavirus does not show this mutation pattern. While there are multiple strains of hantavirus, previous outbreaks have shown very little mutations within a strain (21). In fact, a 2025 study found that even after passing the Andes strain of hantavirus from animal to animal 25 times, only a single, non-impactful mutation arose (22). If covid was passed from one animal to the next 25 times, the virus would mutate, possibly severely, in several times in several different places (23). Hantavirus’s low rate of mutation reduces the chance of the virus becoming more deadly or less susceptible to treatments scientists are currently working on (24). The low rate of mutation is one of the things that makes hantavirus less likely to cause a pandemic.
Virology is a game of chess. Virologists make choices based on the available information and try to predict the next move. Unfortunately, this does not always work because viruses are also playing the game. It can be frustrating to watch the news and feel like scientists do not know what they are doing but this is because they must respond to moves the virus makes. The more we know about a virus, the better we can fight it. Right now, we know a lot about Hantavirus. We know that cruise ships are an unusual environment that allows disease to thrive in a way that they cannot on land. We know that the virus is not very infectious. We even know that the virus is unlikely to mutate very much. And importantly, we know how to contain this outbreak so it will not become a pandemic.