Holoendemic

Holoendemic is a term used in epidemiology to describe a disease pattern characterized by very high, persistent transmission within a population. In holoendemic settings, transmission remains strong throughout the year, resulting in high prevalence of infection across all ages, with most new infections occurring in childhood. Adults in holoendemic areas may acquire partial immunity and exhibit fewer or milder clinical symptoms, though they can still harbor infections. The disease burden thus tends to be concentrated in young children, who may experience higher morbidity.

The term is part of a broader endemicity spectrum that includes hypoendemic (low transmission), mesoendemic (moderate transmission), and hyperendemic (high transmission with ongoing infection across ages). Holoendemic differs from hyperendemic in that, although both involve intense transmission, holoendemic emphasizes the overwhelming infection burden in children and a relatively lower clinical disease burden among adults due to acquired immunity.

Public health implications of holoendemic transmission include a focus on reducing transmission intensity and protecting young children, often through vector control measures, prophylaxis, and early treatment. The concept helps characterize transmission dynamics and guide intervention priorities in areas where exposure occurs early and commonly.

Examples: the historic malaria endemicity in parts of sub-Saharan Africa has been described as holoendemic, where most children are infected early in life and adults carry partial immunity. The term can also apply, less commonly, to other pathogens with similar age-specific infection patterns.