>>13814581Chances are a significant portion of people just died, and those that didn't and did suffer brain damage maybe have still been able to function in more primitive societies with little impact to their lives. Though I'm sure there were a lot of cases where they were labelled as being possessed or cursed when personality changes set in. People may not have been able to understand exactly what was going on because they didn't understand the mechanics at play (similar to how people with genuine learning disabilities were labelled as just being "slow").
That being said humans do have innate behaviours when it comes to trying regulate temperature, if you feel hot you will instinctively seek shade or a cooler environment. You will fan yourself or apply cool water. So people with fevers may have attendants or carers to care for them by bringing them water or fanning them if they were unable to do so themselves. If they lived near a body of water they may have gone and sat in a river or lake to help cool themselves.
