But the sickness did not start until five weeks after leaving port. It would have been impossible to have spread from someone already sick if that were the case.
The only conclusion I can come up with is that this is indeed airborne.
"It's hard to establish how this crew was infected, considering that for 35 days, they had no contact with dry land and that supplies were only brought in from the port of Ushuaia," said Alejandra Alfaro, the director of primary health care in Tierra del Fuego.
So they had contact with supply ships during that time.