When the maritime “Yellow Jack,” is flown by ships entering a harbor, it means the ship is under quarantine. According to Adnan Qureshi in his book Ebola Virus Disease: From Origin to Outbreak, the color yellow has historical precedent “for marking houses of infection and maritime marking color for disease. But Qureshi points out that the disease yellow fever probably derived its name from the flag and not from the color of the victim!
