What does a quarantine flag indicate to other vessels?

The quarantine flag, traditionally a yellow flag, signals to other vessels that the ship may have health concerns on board, such as contagious diseases or other medical issues. This flag serves as a precautionary measure to alert other boats and harbor authorities that they should exercise caution and maintain a safe distance. The primary purpose is to protect the health of crews and passengers on surrounding vessels and to ensure the safety of the public. By displaying the quarantine flag, the affected vessel is indicating that it requires medical attention or that it carries potential health risks, which necessitates the notification to others in the area. This practice is an important part of maritime health protocols to reduce the spread of disease.