There could be more cases, incubation period is 6 weeks: WHO on hantavirus

In a press conference, WHO said the overall risk remains low even as three deaths and eight suspected cases linked to cruise ship outbreak trigger international monitoring.

In Short

• Three deaths and eight linked cases triggered cross-border tracing efforts
• The first passenger died before hantavirus was suspected or tested
• Passengers from 12 countries are being monitored after disembarking in Saint Helena

What began as a seemingly unexplained respiratory illness aboard a luxury expedition cruise ship has now evolved into an international public health investigation spanning multiple countries, three deaths and fears of rare human-to-human hantavirus transmission.

Addressing the media during a press conference on Wednesday, the World Health Organization (WHO) said the overall public health risk linked to the outbreak aboard the Dutch-flagged cruise ship MV Hondius remains low.

But officials also warned that more cases could still emerge because hantavirus can have an incubation period of up to six weeks.

The outbreak has already prompted international tracing efforts involving passengers from 12 countries.

FIRST DEATH DID NOT RAISE SUSPICION

According to WHO officials, the first known patient on the ship developed symptoms on April 6 and died onboard on April 11. At the time, hantavirus was not suspected. No samples were taken from the passenger because his symptoms resembled those of several common respiratory illnesses.

Only later, after additional passengers fell ill, did health authorities begin investigating hantavirus as a possible cause.

Last Saturday, the United Kingdom formally notified WHO under the International Health Regulations about a cluster of severe respiratory illness cases linked to the vessel.

So far, eight cases have been identified. Five have been confirmed as hantavirus infections, while three remain suspected cases. Three people have died.

WHO SAYS MORE CASES MAY STILL EMERGE

During Wednesday’s press briefing, WHO officials repeatedly stressed that the current public health risk remains “minimal.” At present, none of the remaining passengers onboard are symptomatic, officials said.

However, the concern lies in the long incubation period associated with hantavirus infections. Symptoms can appear several weeks after exposure, meaning health authorities are continuing to monitor passengers who may already have travelled internationally after disembarking.

“More cases could still be reported,” WHO officials said, while emphasising that there are established public health measures available to contain further spread.

WHO has now informed 12 countries whose nationals had disembarked earlier in Saint Helena. Those countries include Canada, Denmark, Germany, the Netherlands, New Zealand, Saint Kitts and Nevis, Singapore, Sweden, Switzerland, Trkiye, the United Kingdom and the United States.

INTERNATIONAL MEDICAL TEAM BOARDS SHIP

A WHO expert boarded the MV Hondius in Cabo Verde and has since been joined by two doctors from the Netherlands and a specialist from the European Centre for Disease Prevention and Control (ECDC). The international team is expected to remain onboard until the ship reaches the Canary Islands.

Their job now is to medically assess everyone onboard, trace possible exposures and determine whether transmission may have occurred during the voyage itself.

“We have clear guidance for managing situations like this,” WHO officials said during the briefing. “We know the risk mitigation measures. Further spread can be limited.”

Officials also said logistical challenges linked to handling a possible infectious disease outbreak at sea are being actively addressed.

WHY THIS OUTBREAK WORRIES OFFICIALS

Hantavirus is usually transmitted to humans through contact with infected rodents or their droppings. In most cases worldwide, the virus does not spread from person to person. But health experts suspect this outbreak may involve the Andes strain of hantavirus — one of the few variants historically associated with limited human-to-human transmission.

That has revived memories of the 2018 outbreak in Argentina, where infections spread among close contacts in confined settings.

Still, WHO officials urged people not to compare the situation to Covid-19. “This is not SARS-CoV-2,” WHO infectious disease expert Dr Maria Van Kerkhove said during the press conference.

“It does not spread in the same way. Transmission happens when there is close intimate contact.”

She also stressed that most hantavirus strains do not transmit between humans at all, and described the measures being taken onboard as largely precautionary.

The outbreak has once again highlighted how infections can become difficult to control in confined environments such as cruise ships, where passengers spend extended periods in close proximity.

Investigators are now trying to determine whether passengers contracted the virus onboard or during earlier excursions in Argentina before boarding the ship.

That distinction could prove critical.

If the infections originated before the voyage, the incident may remain a contained travel-linked outbreak. But if transmission occurred onboard, it could become one of the rare modern examples of person-to-person hantavirus spread in a confined international setting.

For now, WHO maintains that the overall risk remains low and that the chain of transmission can still be broken.

But with the six-week incubation period still unfolding for many passengers around the world, health authorities are continuing to watch the situation very closely.

- Ends