Tropical sprue was one of the illnesses contracted during the war, so I have looked up a bit more about it.
Tropical sprue is a malabsorption disease marked by inflammation of the lining of the small intestine and characterized by chronic diarrhoea, nausea, malabsorption of nutrients, weight loss and fatigue. This inflammation makes it difficult to absorb nutrients from food, in particular folic acid and vitamin B12. To avoid the complications and morbidity associated with this condition, it must be promptly diagnosed and treated.
Sprue generally occurs in the tropical areas of the Caribbean, India, South Africa and Southeast Asia. It is similar to, but different from, giardiasis, Crohn’s disease, ulcerative colitis and irritable bowel syndrome. It is treated with tetracycline antibiotics to kill the bacteria and with treatment for the malabsorption, by replacing the vitamins, nutrients, and electrolytes that the body is lacking, ie iron, folic acid and vitamin B12. Recovery can be quick and dramatic after the first large dose of folic acid, and folic acid may be enough to improve symptoms on its own. Most people show good outcomes after three to six months of treatment. Non-tropical sprue responds to a gluten-free diet.
At the end of the war, missionary Mildred Dibden had been ill for some while with tropical sprue, and was repatriated for treatment and recovery, leaving her friend Charlotte Bird in charge of the Fanling Babies’ Home. As there was no known prevention for tropical sprue other than avoiding tropical locations, she was advised on her recovery not to return to Hong Kong. However she returned in 1946 to continue her work.
Source: Mainly Healthline