The longer folks stay on the ship, the more victims there will be because cruise ships are metal containers full of Wifi. The Wifi pings and pings some more. This lowers The passengers' electrical immunity with a mild virus turning into a more serious situation.

Our membrane potential is electircal with a negative charge inside our cells. The potential repels viruses and bacteria which are both also negatively charged.

It's an electric system of defense and the Wifi is too, with it's pulsed positively charged ions wreaking havoc sometimes slowly but always surely.