Epidemiology

Infestations in the US are most common among children 3-12 years of age. All socioeconomic groups are affected. It has been suggested that race or ethnicity influences rates of infestation, but head lice are common worldwide.[5][6][7]

True prevalence and incidence data in the US are unavailable as there is no standardized system for collecting such information. Estimates are often based on the sales of pediculicides, a method likely to overestimate the actual incidence of infestations. Prevalence has been estimated in some communities in other countries, revealing significant variation not only between communities but also among schools within the same community.[7] Some examples include Australia (prevalence in school children of 13%, with a range between schools of 0% to 28%), the UK (prevalence of 2%), China (prevalence of 14%, with a range of 0% to 52%), and Tunisia (prevalence of 18%).[8][9][10][11]​ In developing countries, prevalence in children may be up to 60%; in such settings, head lice infestation may also be frequently present in adults.[12]

Infestations are more common in girls than in boys.[2][11]​​[13][14]​​ Head lice do not infest animals.

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