Microbes and disease. A few harmful microbes, for example less than 1 % of bacteria, can invade our body (the host) and make us ill. Microbes cause infectious diseases such as flu and measles.There is also strong evidence that microbes may contribute to many non–infectious chronic diseases such as some forms of cancer and coronary heart disease. Different diseases are caused by different types of micro-organisms.icrobes and disease. A few harmful microbes, for example less than 1 % of bacteria, can invade our body (the host) and make us ill. Microbes cause infectious diseases such as flu and measles.