Hantavirus Outbreak on MV Hondius Cruise Ship Successfully Contained

Passengers from the MV Hondius cruise ship where the hantavirus outbreak first occurred finished their isolation periods this past Sunday. This is a public health success story worth celebrating, because so many worse results were possible. We heard so much about what went wrong during Covid and the various systems that failed, so it’s good to recognise when things go right – even if you won’t hear about it in the evening news.

There were 147 passengers and crew, and on 4 May seven cases of respiratory illness on board were identified as the Andes strain of hantavirus, which has been known to spread from human to human. This was already an extremely unlucky outcome – hantavirus is deadly, with death rates approaching 30% based on recent research, but most strains only spread from animals to humans.

Given the long incubation period of the virus (as much as six to eight weeks), there was concern about how to manage the spread for those on the ship, as well as those who had already left on commercial flights before the outbreak was identified. The 23 nationalities of people involved made this even trickier to manage: which government would take responsibility and who would be in charge?

The worst-case scenario was terrifying. Imagine that the virus wasn’t identified quickly enough. In the early phase of an outbreak such as this, symptoms are often generic and similar to other travel-related illnesses: fever, fatigue, vomiting. Without rapid recognition of hantavirus and intervention, the passengers could have been free to disembark, disperse and go back to mixing in cities and countries across the world.

Say one crew member goes to a crowded market while on shore and then to a restaurant. A couple fly home and throw a birthday party. They pass through airports, public transport, family gatherings and supermarkets. By the time they develop serious symptoms and are identified as carrying hantavirus, secondary cases have already emerged. The chase to break transmission lines and identify contacts gets harder and harder as each day passes and the outbreak travels further from the ship.

What began as a containable crisis becomes a multicountry outbreak. Individual cases become clusters that start to emerge across the world as passengers are repatriated to their home countries. Given the limited medical treatments – there are no approved therapeutic treatments or vaccines – governments are forced to consider various public health mandates to stop the spread, while the public are confused and scared.

Fortunately, that scenario can remain in your imagination – because of how many things went right over the past month and a half. As of today, the hantavirus outbreak seems to have been contained, with a total of only 13 cases, all in passengers who travelled onboard the ship.

What was behind the successful containment? First, the Spanish government and linked public health authorities deserve credit for stepping up when they allowed the ship to dock near Tenerife. By agreeing to take the lead and organising the disembarkation of passengers, and the safe onwards journey to their home countries, Spain reduced the likelihood of wider spread.

Alongside the Spanish government, the WHO issued technical guidance to the 23 countries with passengers on the ship, setting out standardised protocols for isolation, monitoring and clinical management. This helped create consistency across governments, including contact tracing across flights, airports and public transport. The coordination function of the WHO was especially important because while countries might have their own public health agencies, healthcare systems and political orientations, they had to act together to stop a worldwide outbreak.

In conjunction with the WHO, the UK Health Security Agency did an excellent job repatriating British nationals back to the UK and organising their care, testing and monitoring. As with most outbreak responses, there were also contingency plans for how to manage a wider spread to secondary contacts.

We also got lucky that hantavirus isn’t more contagious: we haven’t seen any cases from those exposed on flights or airports before the outbreak was identified, which we might have done with a more infectious virus. Given the incubation period, we would have expected to see linked cases in late May and into early June.

At the same time, it’s not simply luck that those taken off the cruise ship haven’t passed it on to others. What does success look like in public health? It’s often the things we don’t see, the headlines we don’t read, the diseases that don’t develop. In this instance, success means containment, thanks to good leadership, rapid response and worldwide cooperation. It also means being better prepared next time, as 21 countries have now signed up to a coordinated hantavirus research programme based on studying those exposed on the ship. This means we’ll know more about the virus and how to develop effective treatments and vaccines – which is one silver lining from the outbreak.