Not at all the same thing. Measles is a virus, scarlet fever a bacterial infection. That a measles infection might result in an opportunistic bacterial fever is certainly possible.

In English speaking countries there are two diseases called measles, morbilli is the more serious but rubella is the one that causes birth defects. Some think that canine distemper, a similar virus to morbilli, originated when measles jumped the species barrier. The measles vaccine was sometimes used to give dogs immunity to distemper before the distemper vaccine was developed. Some evidence exists that live measles and/or distemper vaccines can grant immunity to cohabitants of the other species but this has not been proven.

Measles epidemics in the New World decimated native populations several times before some residual tribal immunity developed. A measles epidemic among the Inca ruling families led to dynastic instability resulting in an easy conquest by the Spanish. Mumps helped do the same in Mexico. The eastern seaboard of the US had suffered repeated measles and smallpox outbreaks before the English colonized the area. Something, and it may have been measles, depopulated South Africa shortly before European and Central African colonization of the area that had formerly been home to tribes related to the !Kung of the Kalahari.

Hugs,
Erin

= Give everyone the benefit of the doubt because certainty is a fragile thing that can be shattered by one overlooked fact.