Typhus is a disease caused by infection with one or more rickettsial bacteria. Fleas, mites (chiggers), lice, or ticks transmit it when they bite you. Fleas, mites, lice, and ticks are types of invertebrate animals known as arthropods. When arthropods carrying around rickettsial bacteria bite someone, they transmit the bacteria that causes typhus. Scratching the bite further opens the skin and allows the bacteria greater access to the bloodstream. Once in the bloodstream, the bacteria continue to reproduce and grow.
Chickenpox is a very contagious infection caused by the varicella-zoster virus. It mainly affects kids, but adults can get it, too. The telltale sign of chickenpox is a super-itchy skin rash with red blisters. Over the course of several days, the blisters pop and start to leak. Then they crust and scab over before finally healing.