The fact that all members of an immunologically naive population are exposed to a new disease simultaneously increases the fatalities. In populations where the disease is endemic, generations of individuals acquired immunity; most adults had exposure to the disease at a young age. Because they were resistant to reinfection, they are able to care for individuals who caught the disease for the first time, including the next generation of children. With proper care, many of these "childhood diseases" are often survivable. In a naive population, all age groups are affected at once, leaving few or no healthy caregivers to nurse the sick. With no resistant individuals healthy enough to tend to the ill, a disease may have higher fatalities.