"Read a textbook. It will tell you. These are the things for instance on the African continent that will contribute to immune deficiency, various tropical diseases because of poor infrastructure, general levels of poverty don’t get treated. Syphilis untreated or not properly treated, which as it happens is a big problem as I hear, gets treated, the symptoms disappear but in fact… it … that impacts on the immune system. You’ve got to deal with these things."