HPV is a non-enveloped small double-stranded circular DNA virus, and its persistent infection is closely related to condyloma acuminatum, cervical precancerous lesions, and cervical cancer. To date, more than 200 HPV genotypes have been identified.
According to the relationship between HPV and cancer, HPV infected with anal genitalia can be divided into high-risk type, suspected high-risk type and low-risk type. Common high-risk types are: 16, 18, 31, 33, 35, 39, 45, 51. 52, 56, 58, 59 total 12 types; suspected high-risk types: 26, 53, 66, 67, 68, 70, 73, 82 a total of 8 types; low-risk types: 6, 11, 40, There are 11 types of 42, 43, 44, 54, 61, 72, 81, and 89. Among them, low-risk HPV mainly causes wet lesions and CIN, and the probability of causing cervical cancer is less than 5%, while high-risk HPV causes more than 90% of cervical lesions above CINII.
In the type distribution, HPV 16 and 18 are the main categories in cervical cancer. Most types of infection in patients with condyloma acuminata are HPV 6 and 11 type.
Characteristics of HPV infection
The HPV infection process can be divided into three stages: latent infection, subclinical infection, and clinical symptomatic period. Its infection has the following characteristics:
(1) Humans are the only natural host of HPV.
(2) HPV has strict tissue specificity and mainly infects skin and mucosal squamous epithelium. HPV has a certain infection rate in the vulva, genital tract, anus and even the oropharynx of normal people. Its infection and replication and proliferation depend on the differentiation of epithelial cells.
(3) Most (80%) of HPV infections are transient, which is the most common outcome of HPV infection. 90% of HPV infections resolve within two years, and the time to resolve is mainly determined by the HPV type. Low-risk HPV infection takes 5 to 6 months, and high-risk type takes 8 to 24 months.
Special attention: Only a small number of HPV-infected patients have clinically visible lower genital warts (about 1% of HPV infections with condyloma acuminata), squamous intraepithelial lesions and cancer.
(4) HPV infection of the anal reproductive organs is usually transmitted by sexual contact, but direct skin contact is also considered a mode of transmission.
(5) Because all high-risk HPVs spread in the same way, it is extremely common to infect multiple HPVs at the same time.
(6) The immune response plays an important role in the fight against HPV infection, with cellular immunity.
HPV infection and sex life
Young women will contract HPV infection shortly after starting a sexual life, but sex is the main route of HPV infection, not the only way.
Sexual life frequency is not a major risk factor for cervical lesions, and the number of sexual partners is a major factor affecting HPV infection, cervical precancerous lesions and cervical cancer.
Studies have found that the use of condoms can slightly reduce the chance of women getting HPV, but in general the effect of condoms on HPV is extremely limited, as condoms sometimes do not cover all genital skin.
Male factors also play an important role in HPV infection and even cervical cancer. The presence of male penile HPV increases the risk of cervical infection in female sexual partners by a factor of nine. The age of women’s first-time life is also important. The younger the first sexual intercourse, the higher the HPV infection rate.
HPV infection and cervical lesions
According to China’s census data, cervical cancer is rare in married women younger than 30 years old. After 30 years old, the incidence of cervical cancer increases with age, 55-65 years old is high-risk age group, and after 65 years old, it shows a downward trend. . However, the incidence of cervical cancer has become younger in recent years. High-risk HPV is detected in approximately 96% of patients with cervical cancer, and HPV has been recognized as the primary cause of cervical cancer.
It is important to note that persistent infection with HPV is essential for the development of cervical lesions into CINII-III and even cervical cancer. Simple HPV infection does not mean that cervical cancer will occur. The average time from HPV infection to invasive cervical cancer needs 25 to 30 years. This is a long process from quantitative change to qualitative change to gradual change to mutation.
For women with persistent HPV infection, smoking is a synergistic factor for severe cervical intraepithelial neoplasia, and the incidence of cervical cancer in smoking women is higher than in non-smokers.
Cervical cancer screening
Guidelines for cervical cancer prevention and early diagnosis screening suggest that cervical cancer screening should begin at the age of 21.
For women <21 years of age, screening should not be conducted regardless of sexual life or other risk factors. Because women with <21 years of age are rare with cervical cancer, they do not need to be protected by cytology screening.
For women between the ages of 21 and 29, a separate cytology test is recommended every three years. Women with 21 to 29 years of age have a high HPV infection rate, but the incidence of cervical cancer is low. The new ASCCP guidelines do not recommend HPV testing for cervical cancer screening during this time period.
For women between the ages of 30 and 65, it is best to have a combined cytology + HPV test every 5 years, or a separate screening of cytology every 3 years. If the cytology screening is negative and the high-risk HPV test is negative for people aged 30 years and older, the chance of developing CINII or III in the next 4 to 6 years is very low.
Cases with negative cytology over 30 years of age and positive HPV tests should be treated as follows: (1) Repeat the combined test one year later. If the result of the repeated test is ASC-US or higher, or HPV is still positive, a colposcopy should be performed. Otherwise, joint screening is repeated after 3 years. (2) Immediate HPV16 and 18 typing. Any high-risk type is positive for colposcopy. If the high-risk type is negative, the joint test will be repeated 1 year later.
In short, HPV infection, and condyloma acuminata and cervical cancer are three concepts, HPV infection is not equal to genital warts and cervical cancer.