Done. One of the shipwrecked sailors has measles and introduces the disease to the Amerindians in the *South Carolina area. I wonder what might happen there... As to your last question, I have no idea what kind of 16th century medical technology would have been used against measles.
Here is what
Wikipedia has to say on measles introduced to the Old World.
In populations not exposed to measles, exposure to a new disease can be devastating. In 1529, a measles outbreak in Cuba killed two-thirds of the natives who had previously survived smallpox. Two years later, measles was responsible for the deaths of half the population of Honduras, and had ravaged Mexico, Central America, and the Inca civilization.
Now, the
source cited after that entry doesn't actually say that (or if it does I can't find where) so take that with a grain of salt. Regardless, it's evident that this will be devastating and not just to the Carolina natives. All of the Eastern North America was linked through extensive trade routes centered on the Mississippi River.
Now, if we can delay the second contact by a decade or two, will have burned out its epidemic and while the populations will not nearly have recovered, some cushion is a better scenario then no cushion.
I was looking around for medieval European treatments for measles and apparently the only thing that can help in the pre-antibiotic age is a lot of rest. However, I did find
this site which claims the following.
Measles
Symptoms of the measles are runny nose, dry coughing, high fever, sensitive eyes and in rare cases can cause brain damage. Nine out of ten people who come in contact with the virus will catch the disease. But most people will get better on their own,about one of of ten people die. measles started as an animal disease, probably related to distemper (a disease found in dogs). Because people lived with dogs, at some point it evolved to attack people as well. This would have happened around the time that people began living in cities, because the measles virus needs a big population to keep it going (Otherwise it dies out).
I can't vouch for the validity of that site either, and I think we can all agree that Native Americans in 1507 would have been more severely affected than the "most people" referred to in the quote. However, I don't think we necessarily need to assume measles kills off half of all eastern North American populations.
Does anyone else have more reliable data on how various diseases affected the natives?