Quarantine "yellow jack" but this was also a name for yellow fever, which probably derives its common name from the flag, not the color of the victims (cholera ships also used a yellow flag). The plain yellow flag ("Quebec" or Q in international maritime signal flags) probably derives its letter symbol for its initial use in "quarantine", but this flag in modern times indicates the opposite—a ship that declares itself free of quarantinable disease, and requests boarding and routine port inspection. Australia has perhaps the world's strictest quarantine standards. Quarantine in northern Australia is important because of its proximity to South-east
Flag of Saint Helena taken from the colonial seal of the colony. Ships registered in Saint Helena fly the Red Ensign; there is no defaced variant for the territory. Flag of Saint Helena The flag of Saint Helena was adopted on October 4, 1984. It is a defaced (ie. differentiated) Blue Ensign, i.e., a blue field with the Union Jack in the upper hoist-side quadrant and the shield from the coat of arms of Saint Helena centred on the outer half of the flag. The shield features a rocky coastline and three-masted sailing ship, with a Saint Helena plover, also known as a wirebird,