Imagine you wake up tomorrow with a headache, sore throat and fever, perhaps nothing unusual at this time of the year. You drag yourself out of bed and head to your doctor to ask her for something to make you feel better. However, if you had first looked up your symptoms on the net, you would have been surprised to find that headache, sore throat and fever can be caused by 136 different conditions, among them typhoid fever, measles, and brain tumour.