From the Black Death to COVID: why diseases 'love' ships

This is not to say that every cruise is dangerous. The risk depends on the specific infection, sanitary measures, ventilation, age of passengers, itinerary and how quickly the crew and authorities recognise the problem.

The occasion for the new discussion was the outbreak of a rare hantavirus on the cruise ship MV Hondius. Several people have fallen ill, three passengers have died, and authorities in various countries have begun tracing the contacts of those who left the ship early.

The latest information on the hantavirus on the MV Hondius

According to the European Centre for Disease Prevention and Control as of 13 May, there have been a total of 11 cases linked to MV Hondius: eight confirmed, two probable and one inconclusive. Three deaths have been reported. No new cases or new deaths were recorded by ECDC since the previous update. The vessel arrived at the port of Granadilla in Tenerife on 10 May, disembarkation of passengers and part of the crew was completed on 11 May, after which they were repatriated by country. The MV Hondius itself has headed for the Netherlands and is due to arrive there on 17 or 18 May.

The virus identified is Andes hantavirus. It is a rare variant of hantavirus for which person-to-person transmission is possible, but usually requires close and prolonged contact. The ECDC rates the risk to the EU/EEA population as very low.

The Associated Press reports that more than 120 passengers and crew members have been evacuated from the ship in the Canary Islands and are being isolated in different countries. According to AP, the ship must undergo extensive cleaning and disinfection in Rotterdam after the outbreak; operator Oceanwide Expeditions is awaiting separate authorisation from authorities before the ship can set sail again.

In the UK, some of the evacuated passengers are undergoing prolonged isolation. UKHSA reported that 22 passengers and crew were in isolation at Arrowe Park Hospital; all have tested negative and remain symptom-free. Six have already been released to complete their 45-day isolation at home, while a further ten Britons linked to the flight are due to be flown in from St Helena and Ascension for precautionary observation

Details

This case is a reminder: ships can be challenging environments for infection control. On board, people are around each other for long periods of time, sharing facilities, eating in the same areas, and having contact with crew and cabin neighbours. If an infection is transmitted by airborne droplets, aerosols, food, water or surfaces, these conditions can accelerate its spread.

There is a second risk: the ship does not remain isolated forever. Passengers go ashore, transfer to aeroplanes, return home to different countries. So a disease that starts on board can quickly become an international problem for health services.

Such situations have already happened. During the COVID-19 pandemic, the virus spread rapidly on cruise ships and military vessels. Passengers on some liners refused to be accepted by ports, and crews and tourists were quarantined.

But shipboard outbreaks didn't start with COVID. For centuries, sea routes have helped diseases move between regions. It was ships, trade and ports that played an important role in spreading infections long before aviation.

Why it matters

A ship is a near-perfect model of a closed community. If an infection appears on board, it is difficult to isolate it immediately: people have already been in contact with each other and medical options are limited.

Cruise ships are particularly vulnerable, where passengers often include many elderly people. Even common respiratory or intestinal infections can be more dangerous for them than for young and healthy seafarers.

That said, modern ships are safer than they used to be. Since the COVID-19 pandemic, more attention has been paid to ventilation, medical protocols, isolation of those who fall ill, training of shipboard doctors and contact tracing.

But it is impossible to completely remove the risk. Any ship remains a space where people are around for long periods of time, and help may be far away.

Background

Historically, ships have often been the vectors of infection between continents. Before the advent of aircraft, it was sea routes that connected cities, armies, trading centres and colonies.

One of the most famous examples is the Black Death of the fourteenth century. According to one historical version, the plague reached Europe via maritime trade routes from the Black Sea region. Ships carrying sick people and infected rats could carry the infection to Mediterranean ports, from where it spread further.

Later quarantine measures were also often linked to the sea. Suspicious ships could be kept away from ports, and the sick and those arriving from dangerous regions were sent to special quarantine islands - infirmaries.

Today, the approach has changed. Instead of simply keeping a ship out of port, authorities are trying to identify sick people, isolate contacts, conduct testing and safely evacuate patients. But the problem itself remains the same: infection on a ship requires swift and co-ordinated action.

Source

Science X / AFP From Black Death to Covid, ships have long hosted outbreaks looks at why ships have been the site of infection outbreaks throughout history. The text cites examples from the Black Death and influenza of 1918 to COVID-19 and the recent hantavirus outbreak on the cruise ship MV Hondius.