Does anyone know if the ship is flying the yellow flag?
The Yellow Jack ("Quebec") signal flag, is a plain yellow banner that was historically used to signify a vessel was, or might be, harboring a dangerous disease and needed to be quarantined (the flag represents the letter “Q”).
A ship flying two Quebecs ("QQ"), or "Double Quebec", is signaling: "I require health clearance." In both cases, if and when free pratique is granted, the vessel may lower the Quebec(s), raise the national ensign of the port, and do business there. In the event that, for health reasons, the vessel is not granted free pratique, it continues to fly the Quebec, in effect indicating that it is in quarantine until such time as any health concern is resolved.