A study of field volunteers organized by the National Council of Churches found that about three-quarters of health problems were infectious. These include common infectious diseases, such as diarrheal disease and respiratory tract infection, but also tropical diseases such as malaria and tuberculosis. Vaccine-preventable diseases, such as measles, were also reported. (Ref: Lange WR, Frankenfield DL, Frame JD. Morbidity among refugee relief workers. Journal of Travel Medicine. 1994; 1: 111-112.)