The 2023 Westerdam Cruise Case and Rodent Droppings

In March 2023, a passenger on the Westerdam cruise ship tested positive for hantavirus after the ship docked in San Diego. The virus was traced to rodent droppings in the ship's ventilation system and storage areas. Hantavirus does not spread from person to person — it spreads when a person breathes in dust or particles from infected rodent urine, feces, or saliva. The ship had a rodent problem that went undetected until a passenger fell ill.

The passenger developed symptoms — fever, muscle aches, and respiratory distress — about three weeks after boarding. Testing confirmed hantavirus, which is rare on cruise ships but not impossible. The ship was thoroughly cleaned and inspected, and no other passengers or crew members were found to have contracted the virus. The incident prompted the cruise line to review pest control procedures across its fleet.

Key Takeaways

  • Hantavirus spreads through breathing in dust from infected rodent droppings, urine, or saliva — not from person-to-person contact.
  • Cruise ships can develop rodent infestations in ventilation systems, storage holds, and engine rooms where inspections are less frequent.
  • Symptoms of hantavirus appear two to four weeks after exposure and include fever, muscle aches, headache, and shortness of breath.
  • Cruise lines use pest control services, but rodents can still enter ships through cargo, supply deliveries, or gaps in the hull when docked.
  • The risk of hantavirus on a cruise is extremely low, and the 2023 case was an isolated incident, not an outbreak.

How Rodents Board and Hide on Large Ships

Cruise ships are massive floating structures with thousands of compartments, many of which crew members rarely enter. Rodents — typically rats — board ships through several routes: they hide in cargo containers and food deliveries, slip through gaps in the hull when the ship is docked, or climb aboard via mooring lines. Once aboard, they nest in wall cavities, ventilation ducts, storage areas, and the spaces between the inner and outer hulls where they are difficult to detect.

The Westerdam's ventilation system provided an ideal environment for rodents to live and reproduce without being seen. Air handling units, ductwork, and return-air plenums are warm, dark, and often undisturbed. A single pair of rats can produce dozens of offspring in a few months, so a small infestation can grow quickly. By the time a rodent problem is discovered on a ship, the population may already be substantial.

Pest control on cruise ships typically involves regular inspections, traps, and bait stations in known problem areas. However, the sheer size of modern cruise ships — some carry 6,000 passengers and crew — makes complete inspection difficult. Ships also cannot use certain pesticides in passenger areas, which limits treatment options in occupied cabins and public spaces.

Why Hantavirus Poses a Risk in Enclosed Spaces

Hantavirus thrives in rodent populations and is shed in their droppings and urine. When rodent feces dry out, they become brittle and crumble into dust. If that dust is disturbed — by cleaning, air circulation, or straightforward moving stored items — virus particles become airborne. A person who breathes in contaminated air can inhale the virus directly into the lungs, where it can cause infection.

Cruise ships are particularly vulnerable because they are enclosed environments with recirculated air. The ventilation system on the Westerdam, like most ships, pulls air from multiple zones and redistributes it throughout the vessel. If rodents are living in or near the ventilation intake, virus particles can be drawn into the system and spread to other parts of the ship. This is why the 2023 case prompted when ready concern — the potential for wider exposure existed.

However, hantavirus infection requires a fairly high concentration of virus particles to establish infection. A single brief exposure to contaminated air is unlikely to cause illness. The passenger on the Westerdam likely had repeated or prolonged exposure to rodent-infested areas, possibly while the ship was in port or during routine maintenance work in affected compartments.

Symptoms and Timeline of Hantavirus Infection

Hantavirus causes an illness called hantavirus pulmonary syndrome (HPS). Symptoms typically appear 1 to 8 weeks after exposure, with most cases showing signs around 2 to 4 weeks. Early symptoms are nonspecific and resemble the flu: fever, muscle aches, headache, chills, and nausea. These symptoms last a few days to a week.

The second phase is more serious. Patients develop a cough, shortness of breath, and chest discomfort as the virus damages the lungs and causes fluid to accumulate. This phase can progress rapidly, and some patients require hospitalization and mechanical ventilation. The fatality rate for HPS is roughly 38 percent in the United States, though outcomes depend on how quickly the patient receives medical care.

The passenger on the Westerdam sought medical attention when respiratory symptoms developed, which allowed for early diagnosis and treatment. Because hantavirus was suspected and confirmed through testing, doctors could monitor the patient closely and provide supportive care. The patient recovered, though recovery from severe HPS can take weeks or months.

How Cruise Lines Responded to the 2023 Case

After the hantavirus case was confirmed, the Westerdam underwent a deep cleaning and professional pest control treatment. The ship's ventilation system was inspected and cleaned, and all areas where rodents had been detected were sanitized. The cruise line notified passengers and crew who had been aboard during the exposure window and provided information about symptoms and when to seek medical care.

No other cases of hantavirus were reported among passengers or crew from that voyage, suggesting that the exposure was limited to specific areas of the ship. The incident did not result in a widespread outbreak, but it did highlight a vulnerability in ship sanitation and pest management. Cruise lines subsequently increased the frequency of pest inspections and improved monitoring of ventilation systems.

The cruise industry also reviewed protocols for detecting and reporting rodent activity. Many lines now use electronic monitoring devices in addition to traditional traps, which can alert crew to rodent presence more quickly. Some ships have upgraded to more frequent deep cleaning of ventilation systems and storage areas.

Preventing Rodent Infestations on Ships

Preventing rodents from boarding a ship is the most effective control method. Cruise lines work with port authorities and cargo handlers to inspect containers and deliveries before they are loaded. Ships also use metal guards on mooring lines to prevent rats from climbing aboard, and gaps in the hull are sealed when the ship is in dry dock.

Once at sea, crew members conduct regular inspections of storage areas, galleys, and engine rooms. Traps and bait stations are placed in high-risk zones, and any signs of rodent activity — droppings, gnaw marks, or damage to stored food — are reported when ready. Food storage areas are kept sealed and organized to eliminate hiding places.

Ventilation systems are maintained and filters are changed on schedule. Some ships now use UV light traps or electronic deterrents in addition to traditional methods. However, no method is 100 percent effective on a ship that visits multiple ports and takes on supplies regularly.

Your Risk of Hantavirus on a Cruise

The risk of contracting hantavirus on a cruise ship is extremely low. The 2023 case on the Westerdam was the first confirmed case of hantavirus linked to a cruise ship in recent history. Millions of people cruise each year, and hantavirus remains rare even in areas where rodent populations are known to carry the virus.

Hantavirus is most commonly acquired on land, particularly in rural areas or in buildings where rodents have nested undisturbed for long periods. Campers, hikers, and people cleaning old cabins or sheds face higher risk than cruise passengers. The enclosed, regularly cleaned environment of a cruise ship is actually less hospitable to rodent populations than many land-based structures.

If you are concerned about rodent-related illness on a cruise, the best approach is to report any signs of rodents — droppings, gnaw marks, or rodent sightings — to crew members when ready. Avoid touching or disturbing areas where rodents may have been active. If you develop fever, muscle aches, or respiratory symptoms within a few weeks of your cruise, mention the cruise to your doctor so they can consider hantavirus as a possible diagnosis, though other illnesses are far more likely.

Frequently Asked Questions

Can you catch hantavirus from another person on a cruise?

No. Hantavirus does not spread from person to person. It spreads only through breathing in dust or particles from infected rodent droppings, urine, or saliva. You cannot catch it from a sick passenger or crew member.

What should I do if I see a rodent on a cruise ship?

Report it to a crew member or the front desk when ready. Do not touch the rodent or attempt to trap it yourself. Crew will notify pest control and the area will be inspected and treated. A single sighting does not mean the ship is infested, but reporting it helps the cruise line monitor the situation.

How long after exposure to hantavirus do symptoms appear?

Symptoms typically appear 2 to 4 weeks after exposure, though the range is 1 to 8 weeks. Early symptoms resemble the flu — fever, muscle aches, and headache. Respiratory symptoms develop later. If you develop these symptoms within a few weeks of a cruise, mention the cruise to your doctor.

Are cruise ships required to report rodent problems?

Cruise ships must comply with health and sanitation regulations set by port authorities and maritime agencies. If a rodent-related illness is confirmed, the cruise line is required to report it to public health authorities. Routine pest control is part of standard ship maintenance, though specific reporting requirements vary by jurisdiction.

Do all cruise ships have rodent problems?

No. Most cruise ships maintain effective pest control and never develop significant rodent infestations. However, because ships visit multiple ports and take on supplies regularly, the risk of rodent exposure is never zero. Regular inspections and preventive measures keep infestations rare.