Could More Hantavirus Cases Still Emerge From the MV Hondius?

As the MV Hondius arrived in Tenerife on Saturday May 10 and began disembarking its remaining 147 passengers and crew for repatriation to 24 countries, the most important question in global health monitoring is not what has happened on the ship. It is what may still happen in the weeks ahead.

The Andes virus — the strain confirmed in the MV Hondius outbreak — has an incubation period of 7 to 39 days, with a median of 18 days, based on the most comprehensive clinical analysis of Andes virus incubation, a CDC study of 20 patients with well-defined exposure periods. The last known symptom onset among MV Hondius cases was April 28. At the maximum incubation period, further cases from the last possible exposure date could emerge until early June 2026.

The WHO Director-General has explicitly acknowledged that "it''s possible that more cases may be reported" — and health authorities across more than 23 countries are now monitoring returned passengers precisely because the incubation window has not yet closed.

Here is what the timeline shows, who is being watched, and what it means practically for anyone connected to this outbreak.

TL;DR

• As of May 9, there are eight cases — six confirmed, two suspected — and three deaths. Two of the deaths have been confirmed as caused by Andes virus.
• The Andes virus incubation period is 7 to 39 days with a median of 18 days. The maximum incubation window from the last possible exposure extends to approximately early June 2026.
• Health authorities across several countries are racing to trace and contain the outbreak. Singapore, Canada, France, the US, and the UK are among those actively monitoring returned passengers or contacts.
• The flight contact tracing dimension extends the exposure network beyond the ship — authorities are completing contact tracing of 82 passengers and six crew members from an April 25 Airlink flight from Saint Helena to Johannesburg.
• "This is not the next COVID," WHO''s chief of Epidemic and Pandemic Preparedness said. "Most people will never be exposed to this."
• The risk of secondary transmission to the broader public remains very low. The risk of being a secondary case is more than 10 times higher in sexual partners than in other family members.

The Incubation Timeline: What It Actually Means

The most precise available data on Andes virus incubation comes from a CDC study published in Emerging Infectious Diseases, which followed 20 patients with well-defined exposure periods — the most complete evaluation of Andes virus incubation period in the scientific literature.

The study found the incubation period from exposure to onset of symptoms was 7 to 39 days with a median of 18 days. In patients with exposure periods of less than 48 hours, the range was 14 to 32 days, median 18 days.

This precision matters for understanding the current monitoring timeline. Some media reports have cited "up to eight weeks" — which comes from broader hantavirus family estimates rather than Andes virus specifically. The more precise figure for Andes virus is 39 days maximum.

Working from the key dates in the MV Hondius outbreak:

• April 1 — ship departed Ushuaia. The index case — the Dutch man who likely acquired the virus during his pre-cruise travels in Argentina and Chile — boarded on this date.
• April 6 — first passenger developed symptoms, according to WHO. This was almost certainly the index case.
• April 28 — last known symptom onset among confirmed cases.
• May 10 — today. Ship arrives Tenerife. Passengers begin repatriation.

If any passenger was exposed to Andes virus on the ship through human-to-human contact as late as late April — the latest plausible date given that symptoms in the known cases had onset through April 28 — the 39-day maximum incubation period extends the potential new case window to approximately June 6.

Because of the illness''s one to eight week incubation period, additional cases may still be identified. Health officials around the world are monitoring passengers who disembarked from the ship in the early days of the outbreak in late April.

The most likely scenario, based on the median incubation of 18 days and the pattern of cases — all with onset between April 6 and April 28 — is that any further cases would have emerged or will emerge within the next two to three weeks. The tail risk extends to early June but becomes progressively less likely as time passes beyond the median window.

The Global Monitoring Picture

As of May 8, passengers are hospitalised in South Africa, the Netherlands, Germany, Saint Helena, Spain, and Switzerland. Beyond those with confirmed or suspected infections, a much larger monitoring operation is underway across multiple countries.

United Kingdom — British health authorities confirmed that two UK nationals have confirmed hantavirus cases, and there is an additional suspected case of a British national who disembarked the ship on the island of Tristan da Cunha. UKHSA has been leading the UK monitoring operation.

United States — passengers in Arizona, Georgia, and California are being monitored. The Georgia Department of Public Health confirmed it is monitoring two Georgia residents who returned home after disembarking from the MV Hondius. They are currently in good health and show no signs of infection.

Switzerland — the Swiss government confirmed on May 6 that a man infected with hantavirus is being treated in Zurich. He had disembarked the ship in Saint Helena on April 22, returned via South Africa and Qatar, noticed symptoms on May 1, isolated himself, and tested positive for Andes virus on May 5.

Singapore — two Singaporean residents, both men in their 60s, are self-isolating and being tested. One has a runny nose but is otherwise well; the other is asymptomatic.

Canada — three people in Canada are self-isolating, including two people in Ontario and one in Quebec. One of those people was not on the cruise but was on the same flight home as two Canadians who were aboard the vessel.

France — eight French nationals who were not on the cruise have been identified as close contacts of a confirmed case. The nationals were on the April 25 flight between Saint Helena and Johannesburg, on which the confirmed case also travelled. One of the individuals is displaying mild symptoms, with diagnostic tests being carried out.

This French case is particularly significant — it represents the first identified potential transmission outside the ship itself, via an international flight. It illustrates how the exposure network extends beyond the passenger list through the contacts those passengers had during disembarkation and travel home.

The Flight Contact Tracing Dimension

Authorities are completing additional contact tracing of 82 passengers and six crew members from an April 25 Airlink flight from Saint Helena to Johannesburg that a Dutch woman who had been on the ship took before she died. KLM said authorities in the Netherlands have also reached out to an undisclosed number of passengers on a second flight that the Dutch woman briefly boarded in Johannesburg before being removed because she was too sick to fly.

This flight contact tracing extends the potential exposure network considerably beyond the MV Hondius passenger list. If the Dutch woman — confirmed as a case — transmitted Andes virus to fellow passengers during those flights, those individuals would be within the incubation window now.

The French nationals identified as close contacts from that Saint Helena to Johannesburg flight — one of whom is displaying mild symptoms — are the most immediate test of whether flight-based transmission occurred. Their test results will be a significant data point in the coming days.

The important context: Andes virus spreads through close, sustained contact — not through casual proximity during a flight. The risk of being a secondary case is more than 10 times higher in sexual partners than in other family members. Brief contact during a flight is considered low risk by infectious disease specialists. But the contact tracing is appropriate given the severity of the illness and the importance of identifying any further cases early.

Why This Is Not Like COVID

This question has been asked repeatedly since the outbreak became public — and the answer from infectious disease specialists and WHO has been consistent and clear.

"This is not the next COVID, but it is a serious infectious disease," WHO''s chief of Epidemic and Pandemic Preparedness and Prevention said. "Most people will never be exposed to this."

The biological reasons are specific and important:

Transmission requires close, sustained contact. Andes virus does not spread through casual airborne transmission the way SARS-CoV-2 did. It requires prolonged intimate or close physical contact with a symptomatic individual — the household and healthcare worker pattern that has characterised all previous Andes virus person-to-person clusters.

No asymptomatic spread. Unlike COVID-19, where asymptomatic individuals were major transmission drivers, Andes virus transmission appears to require symptomatic illness. People who feel well are not silently spreading the virus.

Previous outbreaks have been contained. The 2018 Epuyen outbreak in Argentina — the largest documented Andes virus person-to-person cluster — produced 34 cases and 11 deaths in a small town before being contained. It did not spread beyond the immediate community.

The fatality rate, while high at approximately 40%, is not a pandemic driver. Viruses that kill a large proportion of those infected tend to be self-limiting — they run out of hosts before they can spread widely.

The WHO Director-General noted that the Andes virus "spreads between humans only after prolonged and very close contact" and assessed the public health risk as low.

What Former Passengers Need to Know Right Now

If you were aboard the MV Hondius on its April 2026 voyage, or had close sustained contact with someone who was, the incubation window is still open.

The symptom timeline to watch: Based on the CDC data, the median time from exposure to symptoms is 18 days. If exposure occurred in late April — the latest plausible date from the ship — the median expected onset would have been around mid-May. The maximum incubation extends to approximately 39 days from last exposure.

What to watch for: Early symptoms of Andes virus are non-specific and easily mistaken for influenza — fever, severe muscle aches particularly in the thighs and hips, headache, fatigue, dizziness, and sometimes nausea and abdominal pain. The critical warning is rapid respiratory deterioration — coughing, shortness of breath, and chest tightness — which can follow within days and requires immediate emergency care.

What to do: If you develop any of these symptoms before the window closes, do not wait to see if they resolve. Go to an emergency department, disclose that you were aboard the MV Hondius, and insist on specialist infectious disease assessment. Early hospitalisation and intensive supportive care are the most important determinants of survival. There is no specific antiviral treatment.

Respond to official communications: Health authorities in your country of residence will have received passenger manifest information and may be attempting to contact you. Responding to these communications and following the guidance provided is important.

Frequently Asked Questions

How long is the Andes virus incubation period? The most precise available data comes from a CDC study of 20 Andes virus patients with well-defined exposure periods. The incubation period was 7 to 39 days with a median of 18 days. Some general hantavirus guidance cites "up to 8 weeks" — which reflects the broader hantavirus family range. For Andes virus specifically, the maximum is 39 days. From the last plausible exposure date on the MV Hondius, the maximum incubation window extends to approximately early June 2026.

How many cases are there now and where are patients? As of May 9, 2026, there are eight cases — six confirmed by PCR, two suspected — and three deaths. Patients are hospitalised in South Africa, the Netherlands, Germany, Saint Helena, Spain, and Switzerland. Over 62 passengers from 23 nationalities are under active monitoring across multiple countries including the UK, US, Canada, Singapore, France, and others.

Could there be more cases from the MV Hondius? Yes — the WHO Director-General has explicitly acknowledged this. The maximum incubation period means the monitoring window has not yet closed. The most likely scenario based on median incubation data is that any further cases would emerge within the next two to three weeks. The tail risk extends to early June but becomes progressively less likely as time passes beyond the median window.

Is there a risk to people who were on the same flights as affected passengers? This is being actively investigated. Eight French nationals on the April 25 Saint Helena to Johannesburg flight — not MV Hondius passengers — have been identified as close contacts of a confirmed case, with one displaying mild symptoms. Infectious disease specialists consider brief flight contact low risk, but contact tracing is appropriate given the severity of illness. Results from those being tested will be an important data point.

Why is the WHO still saying the public risk is low? Because Andes virus biology makes widespread community transmission very unlikely. It requires close, sustained contact — not casual airborne exposure. It has no documented asymptomatic spread. All previous Andes virus person-to-person clusters have been contained within households and healthcare settings. The 2018 Argentina super-spreader event — the largest on record — produced 34 cases before containment. The virus''s biology does not support the kind of exponential community spread that characterised COVID-19.

What should I do if I feel unwell and was on the MV Hondius? Go to an emergency department immediately — do not wait to see if symptoms resolve. Disclose that you were aboard the MV Hondius on its April 2026 voyage. Insist on specialist infectious disease assessment. Early hospitalisation significantly improves outcomes. There is no specific antiviral treatment — management is supportive care including oxygen, fluids, and in severe cases mechanical ventilation.

The Bottom Line

The MV Hondius outbreak is entering its most critical monitoring phase. The ship is docking. Passengers are dispersing to 24 countries. And the Andes virus incubation window — while narrowing — has not yet fully closed.

The biology of Andes virus means this is not a situation that should generate widespread public fear. Person-to-person transmission requires sustained close contact. Community spread has never been documented beyond small household clusters. The WHO''s assessment of low public risk is well-founded and consistent with everything known about this virus.

But for the specific population connected to this outbreak — former passengers, their close household contacts, and the flight contacts being traced — the monitoring period is active and the symptom awareness guidance matters. The six-week window closes in early June. Until then, anyone in this group who develops fever, muscle aches, or respiratory symptoms should seek emergency care immediately and disclose the connection.

We will continue to update this article as new cases are confirmed or the monitoring period closes.

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Related reading: Andes Virus: Person-to-Person Transmission Explained · What Is Hantavirus? The MV Hondius Outbreak Explained

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