A virus is a small parasite that cannot reproduce by itself. Once it infects a susceptible cell, however a virus can direct the cell machinery to produce more viruses. The most common type of viral disease is the common cold, which is caused by a viral infection of the upper respiratory tract (nose and throat). Chikungunya disease is mostly confined to people living in tropical Africa and Asia and is characterized by a sudden and severe fever, skin rash and joint and muscle pain. Infection with the virus, spread by two mosquito species, typically is not fatal but can cause debilitating symptoms including fever, headache and severe joint pain lasting weeks or months. There is no current treatment and no licensed vaccine to prevent it. Scientists at the National Institute of Allergy and Infectious Diseases, Texas branch of Purdue University have developed a working vaccine for Chikungunya. Several vaccine candidates have reached the stage of human clinical trials. The progress achieved so far suggests that the development of a safe and effective CHIK vaccine is within reach.