Beriberi is a nervous system ailment caused by thiamine (vitamin B1) deficiency; its symptoms include weight loss, emotional disturbances, impaired sensory perception (Wernicke's encephalopathy), weakness and pain in the limbs, and periods of irregular heart rate. Edema (swelling of bodily tissues) is common. In advanced cases, the disease may cause heart failure and death.
Due to the lack of food and especially nutritious food, many American POWs in the Kalihi Valley camp contracted beriberi. Jim Peterson was educated in the diseases' details by observing his fellow prisoners and by contracting it himself. For instance, he had not realized there was a "wet" beriberi and a "dry" beriberi. With the wet cases, men retained fluids and swelled into a parody of good health. Dry cases had a lean and hungry look with fiery pins and needles pain in their hands and feet.
Beriberi was one of many diseases American soldiers stranded on the Bataan Peninsula in 1942 had to deal with. The Associated Press reported on this dire situation, which added fuel to the anti-war fire burning in the country.