The HPV infection prevalence vary considerably from geographically to populations. Globally, the highest HPV infection rate is Sub-Saharan (25.6%), South America (14.3%), Asia (8.7%), Europe (5.2%) of women with normal cytology, .Even within a country, the HPV infection rate varies., It is 28.4% in northeast china, 20.16% in south China and 14.2% in northwest China[13–15]. The prevalence of neighboring southwest provinces is 26.2% in Chonqing, 16.95% in Guizhou, 12.9% in Yunnan[16–18]. For Sichuan, the fourth largest population province located in southwestern China, several studies have investigated its HPV epidemiology and genotype distribution, but the HPV infection prevalence varies, ranging from 10.15–31.3% [7–12]. In our study, the HPV infection prevalence of the total population is 23.84%, which is basically consistent with the result of Li et al (24.1%). By further analyzing of population, we found HPV infection prevalence of HEC group is significantly lower than that of OGOC group, which is 15.29% and 37.62% respectively. Among the HPV studies related to Sichuan Province, there is only one focused on the HEC population, and the prevalence of HPV infection is 12.6%. But this study only calculated the high-risk HPV, which may result in the lower prevalence rate than ours. For OGOC population, our prevalence rate is slightly higher than that of Zhu’s study (32.0%). Compared to other province of China, our result of HEC group is lower than that of Guangdong (17.25%) and Zhejiang (19.5%)[13, 19]. Our result of OGOC group is higher than that of Hubei (17.68%), Guangdong (20.16%) and Zhejiang (22.3%), but lower than that of Fujian (38.3%)[13, 20–22]. Thus, women in Sichuan area are facing with the great threat of HPV infection, especially the women undergoing gynecological clinical symptoms.
Concern to the age of infected women, we found prevalence of HPV infection reached a peak at 21–30 years and 41–50 years group. This double peak result also appeared in other area of China, such as Hangzhou and Chongqing[18, 21]. However, after dividing the population into different groups, we found the prevalence of HPV reached peak at 41–50 years group in HEC group, but at 21–30 years group in OGOC group. A possible explanation is young women have frequent sex and their immune systems are not sensitize to HPV infection, which result in a high infection rate in 21–30 years group. The high infection rate of 41–50 years group may due to reduced immune functions[21, 23, 24]. This double peak result remind women of 21–30 or 41–50 years old should pay more attention to the HPV infection.
In our study, among the HPV positive population, we demonstrated the single genotype infection was the most common form, accounted for 62.06% in total, 74.36% in HEC and 54.01% in OGOC HPV positive women. And the most genotype of coinfection is Septuple Infection. These results are basically consistence with data of Tao et al. .
According to HPV prevalence survey, the most prevalent genotype worldwide is HPV 16 (2.41%), followed by HPV 58 (1.25%) and 31(1.07%). However several studies have demonstrate than HPV16, 52, 58 is the major infection genotype in China[13, 20–22]. In our study, the three most prevalent HPV types were HPV 52 (5.02%), 58 (3.61%), and 16 (3.24%) in the total screening population. Among the HPV positive women, HPV 52 genotype is the most prevalent genotype in Sichuan area, which consist with the data of Li et al, a pattern that was also seen Yunnan and Guizhou Province. However, in a previous study about Sichuan, HPV 16 has been identified to be top prevalent genotype (19.4%). In this study, HPV 52 was the second with 17.0%.Even though there are some discrepant results, the most prevalent genotype in Sichuan area were HPV 58, 16, 52. Among the low-risk HPV genotypes, HPV CP8304 is the most prevalent genotype in both HEC and OGOC group, which is consistent with Le’s research. In OGOC group, HPV 16, 18,6, 11 subtype detections were significantly higher than HEC group, and HPV 53 and CP8304 subtype detections were significantly lower than HEC group. This information may be meaningful for the generating strategies for both cervical cancer screening and vaccine exploitation.
Persistent infection of high-risk HPV is strong carcinogenic factor to induce cervical cancer. In present study, the prevalence of high-risk HPV is 81.41%, 88.57%, and 100% in ASCUS, LSIL and HSIL respectively. The top three genotypes were HPV52, 16, 58 in ASCUS, HPV 66, 58/16/39, 52 in LSIL, HPV 58 in HSIL. HPV 52, 58, 16 accounted for 41.84% of cytology abnormalities. These results is consistent with the data of He et al, except the HPV 66, 39 in LSIL, which may due to the bias of sample size.
Among histological abnormalities, the prevalence of high-risk HPV is 89.83%, 96.30%, 100%, and 100% in CIN Ⅰ, CINⅡ, CIN Ⅲ and CA. The top three genotype is HPV 58 (21.62%), 52(27.03%), 16(21.62%) in CIN Ⅰ group, HPV 16 (70.59%), 52/33(23.52%), 51/39(11.76%) in CINⅡgroup, HPV 58/16 (50%) in CIN Ⅲ and HPV16/18/51/58 (25.00%) in CA group. HPV 52, 58, 16 accounted for 56.52% of histological abnormalities, which was consistent with several studies that investigated the relationship between HPV genotype and histological abnormalities in Sichuan area. These studies demonstrated HPV 16, 58, 52 infection accounts for a large percentage of histological abnormalities [10, 11, 25] [26, 27].
HPV vaccines was introduced to China in 2017. The bivalent vaccine (Cervarix, targeted at HPV16/18) is available since August 2017, and the quadrivalent vaccine (Gardasil, targeted at HPV6/11/16/18) is available since December 2017 in Sichuan province. Thus, our study is a survey before the mass use of HPV vaccine in Sichuan area. According to our study, these tow kind cannot provide enough protection because of the high prevalent of HPV 52, 58 genotype. Therefore, the nonavalent vaccine (Gardasil, targeted at HPV6/11/16/18/31/33/45/52/58) is more suitable for women of Sichuan province, which should be introduced as soon as possible. And according to He’s study, at least half women in western China are willing to take the HPV vaccine, which is beneficial to the prevention and treatment of HPV infection.
There are several limitations in this study. One is absence of data of other area in Sichuan province, which meant these results may not represent all women in Sichuan.. Second, detailed information of population was not available for us to evaluate the effect of these characteristics on the prevalence of HPV infection. And the case of cervical cytology or histology abnormalities is limited. Therefore, larger and prospective studies about the mechanism are also needed to validate our findings.