Rare Hantavirus Outbreak on Cruise Ship: Causes and Risks

Hantavirus Outbreak Aboard MV Hondius: What You Need to Know

Cruise ship outbreaks typically involve norovirus or COVID-19, but a recent and rare incident involving the MV Hondius has brought a different, more deadly pathogen into the spotlight: hantavirus. Currently moored off the coast of Cape Verde, the vessel is the center of an international health investigation after the virus sickened several people and claimed three lives.

While hantavirus is traditionally associated with land-based environments—specifically the inhalation of dust contaminated by rodent waste—its appearance on a cruise ship has raised urgent questions about zoonotic transmission and the possibility of person-to-person spread.

The MV Hondius Incident: Current Status

The MV Hondius, operated by Oceanwide Expeditions, is currently under scrutiny after reports of multiple infections. According to the World Health Organization (WHO), the outbreak has affected seven people in total: three deaths and four other illnesses.

Confirmed cases include a British citizen who was evacuated to South Africa and a 69-year-old Dutch woman. A third passenger, who presented with a mild fever, is currently considered a suspected case. Maria Van Kerkhove, the WHO’s director of Epidemic and Pandemic Preparedness and Prevention, stated in a May 4 briefing that the risk to the general public remains low. The ship is scheduled to continue to Spain’s Canary Islands, where health officials will conduct a thorough disinfection and a comprehensive investigation.

What is Hantavirus?

Hantavirus is not a single entity but a group of more than 50 different viruses. While these viruses primarily infect rodents, moles, and some bats, they can occasionally jump the species barrier to humans—a process known as zoonotic infection.

There are two primary categories of hantavirus based on geography and symptoms:

• New World Hantaviruses (Americas): These can cause Hantavirus Pulmonary Syndrome (HPS), a severe respiratory disease. This form is particularly dangerous, with fatality rates reaching up to 35%.
• Old World Hantaviruses (Europe and Asia): These typically cause hemorrhagic fever with renal syndrome, which can lead to kidney failure and internal bleeding. Fatality rates for these strains range from less than 1% to 12%.

How the Virus Infects the Body

Hantaviruses are RNA envelope viruses. Their structure includes a protein shell encased in a membrane studded with glycoproteins. These glycoproteins act as a mechanism to latch onto a specific protein on human cells called protocadherin-1 (PCDH1).

Once the cell engulfs the virus, the acidic environment of the cell’s endosome triggers the glycoprotein to fuse the virus’s membrane with the cell’s membrane. This releases the viral RNA into the cell, effectively hijacking the cell’s machinery to produce new virus particles.

Transmission: From Rodents to Humans

Humans typically contract hantavirus by breathing in aerosolized particles of infected rodent urine, feces, or saliva. Activities that stir up dust—such as sweeping or vacuuming areas where rodents have nested—can release the virus into the air.

Can it spread between people?
Person-to-person transmission is extremely rare. However, it has been documented with the Andes strain of the virus in Chile and Argentina. Epidemiologists note that such transmission generally requires very close contact, such as kissing or sexual contact. In the case of the MV Hondius, the WHO is operating under the assumption that some human-to-human transmission may have occurred among very close contacts, such as spouses or cabin mates.

Investigating the Cruise Ship Source

Experts are currently exploring two primary theories regarding how the virus reached the passengers:

1. On-board Infestation: Infected rodents may have been present on the ship, with their excrement becoming aerosolized during routine cleaning or vacuuming.
2. Pre-departure Exposure: Since hantavirus has an incubation period of one to eight weeks, passengers were exposed on land in Argentina—where the virus is endemic—before boarding the cruise. The WHO suggests that some victims may have contracted the virus during wildlife excursions in Argentina.

Recognizing the Symptoms

Early symptoms of hantavirus are often non-specific and can be mistaken for the flu. These include:

• Fever and chills
• Severe muscle aches (particularly in the thighs, hips, and back)
• Headache and dizziness
• Gastrointestinal issues, including nausea, vomiting, and abdominal pain

If the virus progresses to the lungs, patients experience coughing and shortness of breath as the lungs fill with fluid, leading to respiratory failure.

Looking Forward

The investigation into the MV Hondius will provide critical data on how hantaviruses behave in confined, high-density environments like cruise ships. While the risk to the general public remains low, this incident underscores the ongoing threat of zoonotic diseases and the importance of rigorous sanitation and wildlife monitoring in travel hubs.