[evan_au (OP)]

There were several severe outbreaks of COVID-19 on cruise ships - one was quarantined in Japan for a month, while another disembarked many cases in Sydney without testing.
- The confusion in Sydney seemed to be caused by the assumption of port staff in Sydney that if there were any COVID-19 cases on board, they would have been diagnosed on board and notified
- At that time, there were no commercially available antibody tests for COVID-19 (and the ones that are available 6 months later have questionable accuracy); even if there were one available, you could not practically deliver to a ship  at sea.
- Or, indeed, to doctors in many countries around the world

So that leaves the possibility of diagnosis via PCR (Polymerase Chain Reaction to multiply small DNA/RNA samples), which can work for any pathogen, including a novel coronavirus. This has been the gold standard for COVID-19 diagnosis on land-based laboratories. But is this technology now small enough and cheap enough (and robust enough) to install on a cruise ship?

Then you have the problem of detecting the new pathogen. This could be done by sequencing all the DNA in the sample, and looking for snippets of the new pathogen. Would these expensive machines be affected by the motion of a ship at sea?

Or could you synthesize RNA or single-stranded DNA for a characteristic snippet of the new pathogen, anchor it to some glassware, and wash the PCR-multiplied DNA over it? This might allow detection of a new pathogen without a full DNA sequencing capability.

If future disease outbreaks are also accompanied by rapid publication of a pathogen genome, would cheap and robust PCR+DNA synthesis allow rapid testing and diagnosis in remote locations like cruise ships (and in many countries around the world)?

PS: I have a vested interest in this - I quite enjoy cruising, and I would like to return as soon as it is safe (after a tested vaccine becomes available!).

[Bored chemist]

Cruise ships have swimming pools because the passengers asked for them...

[alancalverd]

Cruise ships now have up to 6000 passengers and 2000 crew. The UK's entire  "world beating test, track and trace" system can just about handle 200,000 PCR tests in a day, with a turnround of at least 24 hours, so your ship will need to be very well organised!

Sympathy, anyway. I've had the cruise of a lifetime (Faeroes, Iceland, Greenland) cancelled and, being a realist, I've turned down a 150% voucher for next year to spend the refund on a new greenhouse.