Infectious Disease Doctors Explain the Difference Between Hantavirus and COVID-19—and How They Spread

Information about the hantavirus outbreak linked to the MV Hondius cruise ship continues to grip the world. To date, 11 people have either had a confirmed or suspected case of hantavirus linked to the cruise ship outbreak, Tedros Adhanom Ghebreyesus, Ph.D., director-general for the World Health Organization (WHO) shared in a press conference on Tuesday.

Three people have died as part of the outbreak, and there are also reports of cruise ship passengers who are seriously ill. One is a French woman who is in critical condition and on life support at a Paris hospital, per NBC News.

Some cruise ship passengers are quarantining around the world, including in the U.S. But some people left the cruise ship early and are not part of those quarantines. Currently, health officials in at least seven states are monitoring those who were either on MV Hondius or had contact with former passengers.

More cases of hantavirus may surface, Ghebreyesus said. “The incubation period is also six to eight weeks. So, because of the interaction while they were still in the ship, especially before they started taking some infectious prevention measures…we would expect more cases,” he added. The form of hantavirus behind the outbreak is the Andes virus, which is slightly different from other forms of hantavirus.

The story is eerily similar to how COVID-19 originally spread, raising some obvious comparisons between the two viruses. “I understand why people are making the comparison between COVID-19 and Andes virus right now,” says Richard Ricciardi, Ph.D., professor and executive director at the Center for Health Policy and Media Engagement at The George Washington University. “There is an active, highly publicized Andes virus outbreak linked to a cruise ship, and the words ‘respiratory illness,’ ‘quarantine,’ ‘travel,’ and ‘person-to-person transmission’ understandably invoke traumatic memories of COVID-19.”

But infectious disease doctors stress that hantavirus is not the same as COVID-19, although there is some overlap. Here’s what you need to know about hantavirus vs. COVID-19, plus why doctors don’t think this will spark the next pandemic.

Meet the experts: Amesh A. Adalja, M.D., an assistant professor at the Johns Hopkins Bloomberg School of Public Health; Thomas Russo, M.D., a professor and chief of infectious diseases at the University at Buffalo in New York; Richard Ricciardi, Ph.D., professor and executive director at the Center for Health Policy and Media Engagement at The George Washington University

Hantavirus vs. COVID-19

Hantavirus and COVID-19 are two very different viruses, points out Amesh A. Adalja, M.D., an assistant professor at the Johns Hopkins Bloomberg School of Public Health. But, given the COVID-19 pandemic, comparisons are natural with the general public.

“People think every pathogen is similar to every other pathogen,” Dr. Adalja says. “Anytime they hear about something causing a public health emergency, they just jumped to COVID or view it through a COVID lens.”

Here’s how these two viruses compare, plus where there are similarities.

They can spread in slightly different ways.

Andes hantavirus is the only form of hantavirus know to spread between humans, according to the Centers for Disease Control and Prevention (CDC).

The Andes virus can spread through contact with infected rodents or their urine, saliva, or feces; by touching an object or surface contaminated with the virus and then touching your mouth, nose, or eyes; or through close contact with a person who is sick with Andes virus, per the CDC. “Andes virus strain is unusual because it is the only hantavirus known to spread person-to-person, but that spread is rare and generally requires close or prolonged contact with someone who is ill, including direct contact, enclosed-space exposure, or exposure to body fluids,” Dr. Ricciardi says.

COVID-19 is usually spread through person-to-person transmission. Specifically, the virus spreads when an infected person breathes out droplets and very small particles that contain the virus, per the CDC. Others can breathe in the droplets and particles, or they may land on a person’s eyes, nose, or mouth and make them sick. It’s also possible to get COVID-19 from touching an infected surface and then touching your eyes, nose, or mouth, per the CDC.

These viruses have different levels of contagiousness.

COVID-19 is considered a highly contagious illness. But data on the contagiousness of the Andes hantavirus is a little less robust, according to Thomas Russo, M.D., a professor and chief of infectious diseases at the University at Buffalo in New York.

“There haven’t been many outbreaks. The data is very limited,” he says. Instead, scientists generally lean on data from an outbreak that was published in the New England Journal of Medicine. That case report found that the Andes virus has an r-naught or R0 of 2.12. (R-naught is a number that represents the average number of people a single infected person will infect. So, someone with the Andes virus may infect 2.12 others.)

“But there are other examples where someone had the Andes hantavirus, exposed 50 people, and no one was infected,” Dr. Rusos says. “We don’t know for sure what the r-naught is, but it’s certainly much less infectious than SARS-CoV-2, the virus that causes COVID-19.”

Early estimates for the r-naught for SARS-CoV-2 put it around a 4. “This is a dynamic number that can change,” Dr. Russo says. “It tends to be higher at the peak of an outbreak. Then, when all exposures and cases are sorted out, it drops.”

Ultimately, “COVID is much more transmissible and contagious,” Dr. Adalja says.

There is some overlap in initial symptoms.

By now, you’re probably very familiar with the symptoms of COVID-19. However, the CDC lists these as the most current signs of a COVID-19 infection:

• Fever or chills
• Cough
• Shortness of breath or difficulty breathing
• Sore throat
• Congestion or runny nose
• New loss of taste or smell
• Fatigue
• Muscle or body aches
• Headache
• Nausea or vomiting

The Andes hantavirus can cause different symptoms, depending on the stage of the virus someone is in, per the CDC.

Early symptoms of Hantavirus Pulmonary Syndrome, which is a severe respiratory disease caused by the Andes hantavirus, include:

• Fatigue
• Fever
• Muscle aches. (These are more common in large muscle groups like the thighs, hips, back, and sometimes shoulders.)

Half of patients with HPS will also have these symptoms:

• Headaches
• Dizziness
• Chills
• Abdominal issues, including nausea, vomiting, diarrhea, and abdominal pain

“Hantavirus originally presents as a flu-like syndrome and can then evolve into a significant lung disease where you get respiratory failure and potentially die,” Dr. Russo says.

The mortality rate is much higher with Andes hantavirus.

Now that most of the population has some level of immunity to COVID-19, either from previous infection or vaccination, the mortality rate of the virus is considered less than 1%, Dr. Adalja says.

“Andes hantavirus is much more dangerous to an individual patient, with a mortality of about 35%,” he says. The mortality rate of Andes hantavirus may be slightly inflated, though, according to Dr. Russo. “There may be others who were infected with Andes hantavirus who didn’t present to a healthcare provider,” he says. “We may only have data on the tip of the iceberg of people who were exposed.”

But, in outbreak settings, Dr. Russo says that the mortality rate for Andes hantavirus is “significantly higher” compared to COVID-19. “That’s part of what’s scary here is that it has such a high mortality rate,” he says.

Treatment is very different for these viruses.

There are several potential treatments for COVID-19, including antiviral medications like nirmatrelvir/ritonavir (Paxlovid) and molnupiravir (Lagevrio). “There are no specific treatments for hantavirus,” Dr. Adjalja says.

Instead, people who are diagnosed with hantavirus will typically be given symptomatic care, per the CDC.

Will hantavirus become the next COVID-19 pandemic?

Infectious disease doctors say it’s unlikely. “Andes hantavirus is not an efficiently spreading respiratory virus and does not possess pandemic potential,” Dr. Adalja says. “Not every public health emergency constitutes an epidemic or pandemic threat.”

Dr. Russo also notes that genetic sequencing from the Andes hantavirus that infected passengers on the MV Hondius matches previous strains of the virus. “No new mutations have been identified with hantavirus,” he says. “It’s not like this virus is mutating to become more infectious and lethal.”

Still, Dr. Ricciardi recommends doing your best to stay informed about hantavirus and the outbreak. “This is not the next COVID,” he says. “People with known exposure to a confirmed or suspected Andes virus case should follow public health guidance and seek medical care promptly.”

Overall, doctors say it’s important to keep the hantavirus outbreak in perspective. “People have post-traumatic stress disorder of sorts from the COVID-19 pandemic,” Dr. Russo says. “But these are two different beasts. We are not dealing with the next pandemic.”