Hantavirus Outbreak Risk General Public Cruise Ship Group

The hantavirus outbreak has been well-handled – but there are still dangerous days ahead | Devi Sridhar

All the protocols that health experts like me look for have been followed. But outbreaks on cruise ships are notoriously hard to control, says public health expert Devi Sridhar

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Hantavirus: the disease you wish you’d never heard of, as visions of the Covid pandemic flash through your head. I’ve seen lots of breathless coverage and some bizarre takes on social media, so I imagine many people are confused as to what’s going on.

Let me start by saying that this isn’t the Covid pandemic – only Covid was Covid. Previous hantavirus outbreaks have been contained (although none were on a cruise ship). So, for now, the risk to the general public is low – colleagues and I are still carrying on as normal and watching to see whether new infections arise outside the original cruise ship group. Those new infections would be the key step-change determining whether we see further spread and higher-risk public health alerts – or whether we’re at the end of this outbreak.

The first thing to know is that Hantavirus outbreaks happen all the time across the world. You just don’t hear about them. In fact, you probably didn’t hear about the Andes strain hantavirus outbreak in 2018 in Argentina, with 34 confirmed cases and 11 deaths.

Part of what makes the current outbreak unique – and newsworthy – is it being on a cruise ship with about 150 people of 23 nationalities. Cruise ships are notorious for making outbreak control difficult, given the close living conditions, the frequent stops in various ports, the globetrotting nature of passengers and the difficulty in managing a public health response on the ship once a virus is detected.

Do you keep everyone on the ship, with the risk that further people become infected and unwell? Or do you take people off the ship and risk spread in each of their home nations? In this instance, quite a few passengers disembarked before the outbreak was detected and took commercial flights back home, meaning there is already wider potential exposure to the virus. We’ll only know for sure in the weeks to come.

When hantavirus was first mentioned, public health experts were hoping it was any strain beside the Andes strain, which can transmit from human to human and has previously caused super-spreading events. Add to that the fact that it has an incubation period of one to eight weeks, which means that just because someone tests negative today, it doesn’t mean they’re not infected. They could still become symptomatic and infectious later.

We also don’t have an approved vaccine, specific therapeutic or rapid diagnostic test that could be deployed against this strain. This means having to rely on traditional public health measures of isolation and quarantine, N95 masks and stopping chains of infection.

We will know how many others were infected on the cruise ship in a matter of days, so expect more positive cases. We will also know within a few weeks if secondary contacts on flights and elsewhere were infected from passengers who disembarked before the outbreak was identified. None have been identified so far, which is good news. But it’s also early days.

And it’s imperative that those returning to their home countries are supported logistically, medically and emotionally to quarantine for the full WHO-recommended 42 days and do not infect their close contacts, such as family and friends that they might want to see. With the long incubation period, this could mean cases emerging one to two months in the future and more chains of infection to shut down. We’re also in a unique situation of relying on 23 different governments to successfully manage their nationals returning home.

Finally, this has all been made more difficult by the fact that the US has traditionally been the leader in outbreak investigation and response through the Centers for Disease Control and Prevention (CDC). But it recently quit the World Health Organization (WHO) and fired all of the CDC’s cruise inspectors. To its credit, the WHO has taken the lead on the response, working with the staff on the ship and multiple governments to coordinate a coherent and integrated response. All of these different countries are welcoming their nationals back and should all be following a similar containment protocol.

Here, the UK Health Security Agency (headed by Prof Susan Hopkins) has been leading on this – and to its credit has taken a sensible, scientific and proactive response to managing the outbreak. For instance, using self-contained flats at Arrowe Park hospital in Wirral, Merseyside to house all those coming off the ship and ensuring they have a supported isolation arrangement with regular testing and medical assessments. They managed the Kent meningitis outbreak well, too.

Even if more cases arise, scientists are already looking for solutions: vaccine studies are being expedited, existing drugs that might work against hantavirus are being studied and diagnostics are being tested. Knowing some of the brightest minds in the world are looking for solutions will hopefully help you sleep better at night, too.