Scurvy is not just a disease confined to historical pirates but a disease that ravages people today who for various reasons have vitamin C deficiencies. Just like Gout is making a comeback because of people drinking high-fructose corn syrup. Among things you don't need, Gout should be up there near the top.
But, today is about Scurvy, from the wikipedia:
Modern Incidences of Scurvy are still rare but can occur in infants and people with additional health problems.
Scurvy was probably first observed as a disease by Hippocrates. In the 13th century the Crusaders suffered from scurvy frequently, and it has inflicted terrible losses on both besieged and besieger in times of war. Scurvy was one of the limiting factors of marine travel, often killing large numbers of the passengers and crew on long-distance voyages. It even played a significant role in World War I.
The British civilian medical profession of 1614 knew that it was the acidic principle of citrus fruit which was lacking, although they considered any acid as acceptable when ascorbic acid (Vitamin C) was unavailable. In 1614 John Woodall (Surgeon General of the East India Company) published his book "The Surgion's Mate" as a handbook for apprentice surgeons aboard the company's ships. In it he described scurvy as resulting from a dietary deficiency. His recommendation for its cure was fresh food or, if not available, oranges, lemons, limes and tamarinds, or as a last resort, Oil of Vitriol (sulfuric acid).
Symptoms of Scurvy include:
- Dark purplish spots on skin, especially legs.
- Spongy gums, often leading to tooth loss.
- Bleeding from all mucous membranes.
- Bleeding gums.
- Sunken eyes
- Opening of healed scars and separation of knitted bone fractures.
Though the connection between Vitamin C and scurvy was identified specifically in the 1950s, many treatments had been used by sailors and pirates alike in past centuries.
"The plant known as 'scurvy grass" acquired its name from the observation that it cured scurvy, but this was of no great help to those who spent months at sea. During sea voyages, it was discovered that sauerkraut was of extremely limited use in preventing scurvy. In the Royal Navy's Arctic expeditions in the 19th century it was widely believed that scurvy was prevented by good hygiene on board ship, regular exercise, and maintaining the morale of the crew, rather than by a diet of fresh food, so that Navy expeditions continued to be plagued by scurvy even while fresh meat was well-known as a practical antiscorbutic among civilian whalers and explorers in the Arctic. At the time Robert Falcon Scott made his two expeditions to the Antarctic in the early 20th century, the prevailing medical theory was that scurvy was caused by "tainted" canned food.
The use of limes by the British Royal Navy to prevent scurvy gave rise to the name "limey" for an English immigrant in the former British colonies (particularly America, New Zealand and South Africa). The use of this word has been extended to include all British people in American slang. 
In 1927, Hungarian biochemist Szent-Györgyi (who won the 1937 Nobel Prize for Medicine) isolated the compound "hexuronic acid" while working with antioxidant compounds in the adrenal cortex.  It was not until 1932 that the connection between vitamin C and scurvy was established by American researcher Charles Glen King of the University of Pittsburgh.