*4.1.2. Incidence*

It is possible that transmission occurs through semen since it has been demonstrated that HPV DNA is found in sperm in a proportion of 8–64% of asymptomatic men[27]. Studies in vitro shown that HPVs may attach to sperm head, and that infected spermatozoids are able to penetrate oocyte and deliver HPV genome into it. Oocyte can actively transcribed HPV genes,

272 Human Papillomavirus and Related Diseases – From Bench to Bedside A Diagnostic and Preventive Perspective

Other non-sexual skin contact transmission has been documented such as horizontal trans‐ mission via fingers, mouth and fomites[5, 17]. For example, it has been shown that HPV infected individuals may have HPVs in genital sample and in their hands showing that they can not only infect their sexual partners but also themselves somewhere else on their body

According to a recent meta-analysis that included data from more than 1 million women with normal cytology in 59 countries, the prevalence of cervical HPV infection ranges from 1.6% to 41.9%, with a global prevalence estimated at 11.7% [29]. Sub-Saharan Africa (24.0%), Eastern Europe(21.4%),andLatinAmerica(16.1%) showedthehighestprevalencesandtheregionswith the lowest prevalences are: Northern America with 4.7% and Western Asia with 1.7%. Also, it is important to consider that these percentages are probably underestimated as the laboratory methods used to detect HPV do not necessarily included the detection of all HPV geno‐ types[30]. The 5 most common genotypes worldwide are HPV-16, 18, 52, 31 and 58. Typically, HPV prevalence increases rapidly in adolescence following sexual debut, followed by an agerelated decline, and occasionally a second but more modest peak in prevalence among older women in some regions of the world such as in America (Northern, Central and South) and in Europe[31]. Although the reason for this "menopausal" peak is not clear, it could plausibly be attributed to one or more non-mutually exclusive mechanisms, such as reactivation of latent infections acquired earlier in life due to a gradual loss of immunity, or to acquisition of new

infections due to sexual contacts with new partners later in life (cohort effect)[5].

Less research has been conducted to determine the prevalence of HPV in anal tract of women. A prevalence of 42% has been observed in healthy women [32] and by contrast to cervical prevalence that shows an age-related decline, the prevalence of anal infection seems relatively steady in all age groups[33]. Some studies also shown that women with cervical HPV infection had more than three fold increased risk of concurrent anal-cervical infection with a high correlation between the concordance of HPV genotypes, indicating a common source of infection[33]. As anal intercourse is not strongly associated with anal HPV infection in women,

(hands, conjunctive, etc.) as well as other individuals outside sexual contacts[16, 18].

**4. Epidemiology of ANOGenital hpv infections**

**4.1. Anogenital HPV infections in women**

for transmission to occur[28].

*4.1.1. Prevalence*

**Cervical HPV infections**

**Anal HPV infections**
