A suspected Covid-19 outbreak on a cruiseship in Greece proved to be a false alarm and the vessel can continue its journey with all its 1,588 passengers and crew.

The cruise was interrupted when twelve crewmembers on the 98,800-gt Mein Schiff 6 (built 2017) tested positive for the disease and were put in isolation on 28 September.

Subsequent testing, however, showed that the initial results were wrong, Greek authorities announced a day later.

The Mein Schiff 6, a vessel controlled by the TUI Cruises joint venture of German holiday giant TUI and Royal Caribbean Group, will therefore continue its journey on 30 September from Piraeus, Greek coastguard sources told TradeWinds.

Both TUI executives and Greek officials will sigh with relief at the news.

The Mein Schiff 6 is the first cruiseship to ply Greek waters after a six-month hiatus for such trips caused by the coronavirus.

An outbreak on board could have spelled the death-knell for Greek efforts to revive the cruise scene.

It would also have dealt a heavy blow to TUI, which has bet heavily on the Greek market to sustain its business in Germany. Greece has been the first Mediterranean country in which TUI Cruises started its sailing programme this year.

The incident nevertheless shows that conducting coronavirus tests on ships and interpreting them correctly can be fraught with uncertainty.

The initial, mistaken tests were carried out onboard the Mein Schiff 6 by a private contractor hired by TUI. Their results were just “marginally positive,” Greek health official Gikas Mayiorkinis told reporters in a briefing on Tuesday.

“It’s a matter of concern to us that the laboratory failed to observe the protocol for [assessing] the positivity of the sample,” Greek deputy minister for civil protection Nikos Hardalias said in the same briefing.

Given the heightened risk of large breakouts on cruiseships, both TUI and the Greek government ordered a triple-check of the suspected victims as well as their known contacts. All subsequent tests turned out negative.

Mein Schiff 6 is underway in the Aegean with 666 crewmembers and 922 passengers. The vessel left the Greek port of Heraklion late on Sunday and was en route to Piraeus and later to Corfu.

TUI and Greek authorities said they put maximum-hygiene rules in place to prevent any outbreaks on board, such as a 60% capacity ceiling.

Greece has been one of Europe’s most successful countries in coping with the coronavirus. In recent weeks, however, the number of cases has shot up and reached record levels, albeit from a very low base.