**4. Epidemiology of ANOGenital hpv infections**

### **4.1. Anogenital HPV infections in women**

#### *4.1.1. Prevalence*

#### **Cervical HPV infections**

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].

#### **Anal HPV infections**

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, other important route of transmission have been suggested such as no penetrative sexual contact (for example, involving the fingers or mouth of partner), non-sexual contact, or HPV shedding from the vagina to the anus given the close proximity of these two areas[33, 34].

#### **Vaginal and vulvar HPV infections**

It has been suggested that vaginal and vulvar HPV infections are also very common in healthy women although much less data in available for these site specific areas. Some studies have detected HPVs in cervicovaginal samples compare to cervical samples and showed positivity for HPV in cervicovaginal swabs are higher compared to cervical specimens suggesting a higher prevalence HPV in the vagina or vulva than in the cervix only[35]. For example, a prevalence of 42.5% has been observed among females in United States using self-collected cervicovaginal specimen[36].
