Holoendemic

A disease is holoendemic when essentially every individual in a population is infected. As the disease is ubiquitous, the young are more likely to express pathogenic responses, whilst the older hosts will carry the disease asymptomatically, or with reduced damage, due to adaptive immunity. Examples of this holoendemic pattern are seen with malaria in areas of sub-saharan Africa (where 75% of the deaths are in children under 5) and trachoma in areas of Saudi Arabia.