An expedition cruise has become the epicenter of a rare Andean virus outbreak, prompting international contact tracing, isolation, testing and genomic analysis to contain the deadly pathogen, which is known to occasionally be transmitted from person to person.
Rapid communication: Andean virus outbreak linked to expedition cruise ship travel, multilateral investigation and response, April-June 2026. Image credit: HD-Warrior80 / Shutterstock
Recent reports published in magazines euro monitoring It highlights the outbreak of the Andean virus on board the Dutch-flagged expedition cruise ship MV Hondius. As of June 18, the virus has infected 13 passengers and crew, three of whom have died. However, no further cases have been confirmed, and although many infected people have been released from isolation, some contacts remain under surveillance. Health authorities are conducting contact tracing and conducting surveillance to monitor infections and the number of infected people.
On May 2, 2026, health authorities in the Netherlands and the United Kingdom (UK) notified the European Center for Disease Prevention and Control (ECDC) and the World Health Organization (WHO) of an outbreak of a serious respiratory infection of unknown origin among the passengers and crew of the MV Hondius. The ship departed Ushuaia on April 1, 2026 and arrived in Praia. From Ushuaia, the ship sailed to South Georgia, Cooper Island, Tristan da Cunha, Gough Island, St. Helena, and Ascension Island, arriving in Praia on May 3.
In this report, an international team of researchers describes efforts to improve outbreak detection, investigation, contact tracing, and ANDV preparedness.
Outbreak detection and case classification
Initial laboratory tests detected hantaviruses, but subsequent tests in Switzerland and South Africa identified members of the orthohantavirus andesense complex as the causative agent. As of June 18, 2026, there is 1 probable case and 12 laboratory-confirmed cases. These included nine men and four women, with a median patient age of 65 years. Three people ultimately lost their lives (fatality rate 23%).
In accordance with WHO guidance, confirmed cases included people with laboratory-confirmed ANDV infection. Probable cases included symptomatic individuals with documented exposure to a probable or confirmed case for which laboratory testing was not possible. Contacts were identified as people who were exposed to an infected or probable case during the confirmed infection.
A high-risk contact is someone with whom you shared eating, toileting, or sleeping facilities without wearing personal protective equipment (PPE), or who had direct physical contact, exposure in care, or close proximity for more than 15 minutes within 2 meters for an extended period of time. Handling personal belongings, clothing, body fluids, or medical waste without wearing PPE and sitting in the same row of cases or within two rows in any direction on an airplane are high-risk exposures.
Health authorities considered zoonotic transmission through exposure to the saliva, urine, or feces of a rodent carrying the virus to be the most likely source of infection for the first case before boarding the ship. Subsequent infections are likely the result of transmission among passengers and crew in the confined spaces of the ship, although investigations into co-exposure and environmental contamination are ongoing. This virus circulates among long-tailed rats (Oligorhizomys longicaudatus) in South America.
Contact tracing and population risk assessment
On May 6, 2026, WHO and ECDC determined that further transmission within the household following exposure on a cruise ship is unlikely. On May 9, ECDC classified all passengers and crew on the ship as high-risk contacts and recommended six weeks of isolation and active observation, except for public health professionals who joined the ship later and consistently used PPE.
Between April 13th and 15th, the ship arrived at Tristan da Cunha. During this period, 10 local residents visited the ship, two stayed overnight, and a further six boarded for St. Helena. The ship docked in St. Helena from April 22 to 24, and 32 people disembarked, including the body of Case 1, who died, and Case 2, Case 1’s partner. A third person who was found to be infected with ANDV also disembarked to visit the island, but later reboarded. During the landing, the second and third patients developed early symptoms of the disease but were not treated. Contact tracing in St. Helena revealed 22 high-risk contacts were isolated. Additionally, 67 low-risk contacts were monitored through passive surveillance.
On April 25, case 2 traveled to South Africa and became ill before departing for the Netherlands. Two days later, Case 3 landed on Ascension Island and was transferred to South Africa for treatment. Case 7 became ill on May 1st after returning to Switzerland and was diagnosed or confirmed in early May.
From May 3 to May 6, the ship remained near the coast of Praia, during which time the fifth and sixth infected persons, along with one person exposed to case 4, were transferred for treatment. On May 6, two doctors and two experts from ECDC and WHO were brought on board to assess clinical symptoms and potential public health risks. Four days later, the ship arrived in Granadilla, Tenerife, carrying 147 asymptomatic people. Cases 9-13 subsequently returned to the country within two days and tested positive for ANDV upon return or during quarantine monitoring.
The remaining crew and medical personnel arrived in Rotterdam on May 18th, and the final PCR and serological tests yielded negative results, and the quarantine for the 61 passengers and crew members who had been quarantined in the Netherlands was subsequently lifted. Health authorities have identified 188 high-risk contacts associated with confirmed cases in seven countries. Most have completed or are expected to complete quarantine by late June, but one close contact was expected to complete quarantine by July 2.
further action
WHO and ECDC recommend testing whole blood, serum, or plasma samples from symptomatic contacts using the PCR protocol established by the European Union Public Health Reference Laboratory (EURL-PH-ERZV). Genetic testing showed that the viral sequences in the five sequenced cases were nearly identical, making them closely similar to the ANDV outbreak in Epuen, Argentina, in 2018.
These preliminary findings support a common source or closely related transmission chains, but interpretation remains cautious pending additional sequencing and epidemiological data. Investigations are underway to understand the route of transmission, identify risk factors, and assess the effectiveness of public health measures. The results of this study are expected to improve our understanding of ANDV infection dynamics and help prepare for and respond to future outbreaks.
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