At the end of November 1915, Sing suffered from myalgia and was confined to the hospital ship HMHS "Gloucester Castle" for almost two weeks. During this time, he was conveyed to Malta, then Ismaïlia, Egypt. While in Egypt, he was also hospitalised with parotitis and mumps, but rejoined his unit at the end of March 1916. Australian soldiers stationed in Egypt including Billy Sing were major customers of Egyptian prostitutes in the local red light districts and brothels. High prices by the prostitutes led to the Wasser red light area becoming the scene of a major riot by New Zealand and Australian soldiers on Good Friday in 1915.