Infestations in the US are most common among children 3 to 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]American Academy of Pediatrics, Nolt D, Moore S, et al. Head Lice. Pediatrics. 2022 Oct 1;150(4):e2022059282.
https://publications.aap.org/pediatrics/article/150/4/e2022059282/189566/Head-Lice
http://www.ncbi.nlm.nih.gov/pubmed/36156158?tool=bestpractice.com
[6]Downs A, Oxley J. Head lice infestations in different ethnic groups. Int J Derm. 2001 Mar;40(3):237-8.
http://www.ncbi.nlm.nih.gov/pubmed/11422534?tool=bestpractice.com
[7]Falagas ME, Matthaiou DK, Rafailidis PI, et al. Worldwide prevalence of head lice. Emerg Infect Dis. 2008 Sep;14(9):1493-4.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2603110
http://www.ncbi.nlm.nih.gov/pubmed/18760032?tool=bestpractice.com
True prevalence and incidence data in the US do not exist as such data are not collected in any standardized way, and are often inferred by the sale of pediculicides, which in itself most likely represents an overestimate of true incidence. Prevalence has been estimated in some communities in other countries, but can vary widely among communities, and even among schools in the same community.[7]Falagas ME, Matthaiou DK, Rafailidis PI, et al. Worldwide prevalence of head lice. Emerg Infect Dis. 2008 Sep;14(9):1493-4.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2603110
http://www.ncbi.nlm.nih.gov/pubmed/18760032?tool=bestpractice.com
Some examples include Australia (prevalence in school children of 13%, with a range between schools of 0% to 28%), the UK (prevalence of 2%), and China (prevalence of 14%, with a range of 0% to 52%).[8]Counahan M, Andrews R, Buttner P, et al. Head lice prevalence in primary schools in Victoria, Australia. J Paediatr Child Health. 2004 Nov;40(11):616-9.
http://www.ncbi.nlm.nih.gov/pubmed/15469530?tool=bestpractice.com
[9]Harris J, Crawshaw JG, Millership S. Incidence and prevalence of head lice in a district health authority area. Commun Dis Public Health. 2003 Sep;6(3):246-9.
http://www.ncbi.nlm.nih.gov/pubmed/14708276?tool=bestpractice.com
[10]Fan CK, Liao CW, Wu MS, et al. Prevalence of pediculus capitis infestation among school children of Chinese refugees residing in mountainous areas of northern Thailand. Kaohsiung J Med Sci. 2004 Apr;20(4):183-7.
http://www.ncbi.nlm.nih.gov/pubmed/15191220?tool=bestpractice.com
In developing countries, prevalence in children may be up to 60%; in such settings, head lice infestation may also be frequently present in adults.[11]Lesshafft H, Baier A, Guerra H, et al. Prevalence and risk factors associated with pediculosis capitis in an impoverished urban community in lima, peru. J Glob Infect Dis. 2013 Oct;5(4):138-43.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3958982
http://www.ncbi.nlm.nih.gov/pubmed/24672174?tool=bestpractice.com
Head lice do not infest animals.