<P> In International maritime signal flags, plain yellow, green, and even black flags have been used to symbolize disease in both ships and ports, with the color yellow having a longer historical precedent, as a color of marking for houses of infection, previous to its use as a maritime marking color for disease . </P> <P> The present flag used for the purpose is the "Lima" (L) flag, which is a mixture of yellow and black flags previously used . It is sometimes called the "yellow jack", which became a name for yellow fever . Cholera ships also used a yellow flag . </P>

Flag flown on a ship to indicate the presence of a disease