COVID-19 Case in Cruise Tested Negative with Original Sample; 2nd New Sample also Tested Negative

Turning back a ship carrying over 2,800 guests and crew members during a cruise because one person is ill would have sounded extreme in any year other than this awful one we’re currently in.

But in 2020, it’s just another unexpected occurrence that we’ve come to expect.

On Wednesday (9 Dec), Royal Caribbean’s cruise ship Quantum of the Seas had to return to Singapore earlier than scheduled after a passenger on board tested positive for Covid-19.

The cruise to nowhere was supposed to be a four-day trip, but turned back on Wednesday (9 Dec) – its third day – due to the infection.

However, after returning to Singapore, disembarking, and carrying out deep cleaning of the ship, the same passenger has tested negative for the disease.

Twice. 

Negative Prior to Boarding, Positive On Board

The confirmed Covid-19 case is an 83-year-old man who reported to the medical centre on the ship with diarrhoea.

According to the Ministry of Health (MOH), he then underwent a polymerase chain reaction test as part of the on-board protocols.

Prior to boarding, the man, along with the other passengers, underwent a mandatory PCR test, but tested negative.

On the ship, however, he tested positive.

As a result, the man was isolated, as was all of his close contacts, and the ship returned to Singapore.

Fortunately, all the man’s close contacts have tested negative for Covid-19.

Original Sample Later Tested Negative; 2nd New Sample also Tested Negative

Then, something strange happened.

The man’s original sample was sent to the National Public Health Laboratory (NPHL) for a follow-up test, according to TODAYonline.

He tested negative. 

A subsequent test of a second fresh sample by NPHL has also come back negative.

MOH said NPHL will conduct another test today (10 Dec) to confirm his Covid-19 status.

In the meantime, all of the man’s identified close contacts will remain in isolation as a precautionary measure.

The Singapore Tourism Board said that all passengers on board the ship started disembarking on Wednesday at 7.30pm, with the process expected to be completed at around midnight.

They will undergo mandatory Covid-19 testing before they are allowed to leave the terminal at Marina Bay Cruise Centre.

Deep cleaning will also be carried out on board the ship.

Royal Caribbean has also cancelled its Quantum of the Seas cruise on Thursday “in an overabundance of caution” after the man’s positive Covid-19 test.

Sailings will resume next Monday (14 Dec), they said.

False Positive? 

If the man tested positive for Covid-19 but then tested negative on two subsequent tests, that surely means the first was a false positive, right?

Not quite. 

In November, the U.S. Food and Drug Administration warned clinical laboratory staff and healthcare providers that false positives can occur with Covid-19 tests, but were referring to antigen tests. 

This man, however, had undergone a polymerase chain reaction (PCR) test.

Antigen tests, while faster, cheaper, and easier to administer, aren’t as accurate as PCR tests.

According to Harvard Health Publishing, while there’s a chance of false negatives occurring –  test that indicates you don’t have the virus when you actually do have the virus – the false positive rate should be close to zero.

“Most false-positive results are thought to be due to lab contamination or other problems with how the lab has performed the test, not limitations of the test itself,” it said.

We’ll just have to wait for the man’s follow-up tests to determine what happened.

Featured Image: Igor Grochev / Shutterstock.com