Around there I woulds imagine. In the Domesday Book the town that my family originated in had a population of 250, that was in 1068, in 1279 the population was about 1500 with about the same area.
I do think though that small pox was a symptom of decline reather than a cause.
Listened to an author of a book on small pox in the US and seemed to spread as different people came into contact with each other. The English or the French gave it to the Indians. It spread across the plains and some plains Indians gave it to the Spanish in New Mexico when they took other Indians there to sell them as slaves. Another aside: Geo Washington had the Americans innoculated against small pox after some British prisoners came up with it. Maybe the most significant strategic move of the war, at least right up there with the French Navy blocking the harbbor at Yorktown.