A lot of people think in the beginning that chickenpox and measles are the same simply because those who are affected get red spots. They are both contagious, and they are considered to be infectious diseases. Take note that one difference between the two is the type of virus that causes these diseases.
Chickenpox is caused by the varicella-zoster virus, while measles is caused by the measles virus. There are also some differences with the type of spots that will appear. The spots in chickenpox will usually contain water inside, which can make them look like they are pimples with pus while the spots in measles will not contain water.