Is HPV infection really only transmitted through sexual contact?

Many people may have seen similar statements such as "HPV infection is caused by X", "HPV infection is caused by her chaotic private life"... When the Man Shuke incident was trending on the Internet, I read the comments and saw many similar statements. Is HPV infection really only transmitted by X?

Of course not! In our land where x is a secret, such misunderstandings will make people underestimate the possibility of being infected with HPV, and may also cause some patients to be slandered or even humiliated without reason, so it is very necessary to let everyone correctly understand the various ways of HPV infection!

Today, let’s start with what HPV is and talk about the ways HPV is transmitted.

01. What is HPV?

What exactly is HPV? HPV is the abbreviation of human papilloma virus, which is a virus that easily infects the squamous epithelium of the human epidermis and mucous membranes [1].

A characteristic of this virus is that it is epithelial-tropic, which means it likes to infect epithelial tissues, such as the epithelial cells of our skin and mucous membranes[2].

I believe that seeing this, you will realize that HPV is not only transmitted through x-ray. After all, epithelial tissue is not only found in x-ray organs, but also in other organs of the body.

In fact, the sites that HPV can infect include the mouth, throat, penile skin, vulva, anus, vagina, cervix and rectum[1][2].

02. What are the ways of HPV infection?

There are several ways that HPV can be transmitted, including:

Sexual transmission[1]: The main route of transmission. Mucous membrane contact during homosexual or heterosexual intercourse can cause infection.

Mother-to-child transmission[1]: It is common for mothers with genital tract HPV to transmit the virus to their newborns during delivery.

Skin-to-mucosal contact[1]: In addition to the cervix, HPV can also infect other parts of the body: the mouth, throat, skin, and anus, and may induce corresponding tumors. After the hands come into contact with HPV-contaminated objects, the virus may be introduced into the reproductive organs when using the toilet or bathing, or the reproductive organs may be infected when they come into contact with HPV-contaminated bath towels, underwear, etc.[3]

Therefore, if HPV-contaminated towels, underwear, public places, public bathrooms, swimming pools, door handles, etc. are not cleaned and disinfected properly, they may also be infected with HPV [4].

Therefore, even if you have never had sex, you can still be infected with HPV! Many people only know that it is transmitted through sexual intercourse, but ignore the possibility of infection through other transmission routes, and thus associate HPV infection with sexual life, which is wrong. Many people also mistakenly believe that HPV infection means a promiscuous sexual life, and that if they have only one sexual partner, they will not be infected. However, even sexually active people who have only had sex with one person can still be infected with HPV [5].

HPV infection has almost no symptoms. Many people do not know that they are infected with HPV, nor do they know that they can transmit the virus to others [6]. People may develop symptoms years after having sex with an HPV-infected person, which makes it difficult to determine when they were first infected with the virus [5]. So it is possible to be infected with HPV with the same sexual partner!

Does this mean that if we take safety precautions and use condoms every time we have sex, we can completely avoid HPV infection? Actually, not really. Using condoms correctly can reduce the chance of HPV infection, but HPV can infect areas not covered by the condom, so HPV that survives on the skin can continue to be transmitted. Therefore, condoms cannot provide complete protection against HPV infection [7].

03. What are the types of HPV?

As can be seen from the above, HPV infection is actually much closer to us than we think! However, most HPV infections can be cleared by the immune system. Most HPV infections are transient and asymptomatic. However, persistent infection with certain types of HPV can lead to precancerous lesions. The time from HPV infection to cervical cancer varies. Usually, persistent HPV infection develops into cervical cancer after 10-20 years of natural evolution[1] [9]. Almost all cervical cancers (99.7%) are related to HPV infection[2] [8].

However, there is not just one type of HPV. More than 200 types of HPV have been discovered [1]. So we often see the number HPV+, which actually refers to different HPV types. Not every type of HPV is dangerous. Researchers divide it into two types: high-risk and low-risk types based on their carcinogenicity [1].

HPV16/18/52/58 are highly correlated with cancer and are therefore considered high-risk types, while HPV6 and other types are considered low-risk types because they rarely develop into cancer[10].

For us, high-risk HPV deserves special attention because it is closely related to cancer, especially cervical cancer. The 2023 ICO/IARC China HPV and Related Diseases Report shows [11] that about 98% of cervical cancer in Chinese women is caused by high-risk HPV.

A systematic review of 198 studies in China in 2019 showed that the high-risk HPV infection rate among the general female population aged 25-45 in China was 19.9%. This means that, on average, 1 in 5 general female population aged 25-45 may be infected with high-risk HPV [13,a]. (General female population includes women with symptomatic outpatient clinics or health check-ups) At the same time, studies have shown that people usually develop high-risk HPV infection soon after starting sexual intercourse [1]. This means that women are often at high risk of HPV infection after having sex.

04. About high-risk HPV

However, the same high-risk HPV has different distribution in the population. For example, the high-risk HPV types that Chinese women are susceptible to are different from those in foreign countries. According to the 2023 ICO/IARC Global and Chinese HPV-related Disease Report, the top three high-risk HPV types infected in Chinese women with normal cervical cytology are HPV52/16/58, and compared with the world, the infection rate of HPV52/58 in Chinese women with normal cervical cytology (4.5%) is nearly twice that of the world (2.5%) [11] [12].

Comparison of the ten most common oncogenic HPV types in Chinese women with normal cervical cytology[11]

Comparison of the ten most common oncogenic HPV types in women with normal cervical cytology worldwide[12]

In recent years, the incidence of cervical cancer has been on the rise, and the age of cervical cancer onset has been getting younger[14]. A study on the epidemiology of cervical cancer showed that the youngest age for diagnosis of cervical cancer can be as young as 17 years old[15,b]. The 2023 ICO/IARC Global and Chinese HPV and Related Diseases Report pointed out that in 2020, there were about 110,000 new cases of cervical cancer and about 60,000 deaths from cervical cancer in China, which means that about 300 women are diagnosed with cervical cancer every day in China, and about 7 women die from cervical cancer every hour[11]. This has to make us alert to the harm of cervical cancer.

05. How to prevent cervical cancer?

So how do you prevent cervical cancer? I believe that over the past few years, everyone's understanding of immunology has greatly improved, so they can blurt out "vaccine". Yes, for a virus that is widely present and easily infected, vaccines are a very good strategy. Vaccination can greatly enhance protection and reduce the risk of HPV infection.

The launch of the HPV vaccine has made cervical cancer the only cancer that can be prevented early and is expected to be completely eradicated[16]. In 2023, China's "Guidelines for Comprehensive Prevention and Control of Cervical Cancer (2nd Edition)" proposed a three-level prevention strategy[14], of which HPV vaccination is the first step.

Three-level strategy for cervical cancer prevention

So when is it necessary to get the HPV vaccine? If women have already had sex, do they no longer need it? Not necessarily. A multicenter, population-based study in China showed [17,c] that the HPV infection rate among Chinese women is bimodal by age: the first peak is between 17 and 24 years old, and the second peak is between 40 and 44 years old.

HPV vaccines are not only effective for women who have never been infected with HPV, because the vaccine is multivalent. Even if infected with one HPV type, the vaccine can also prevent lesions caused by infection with other HPV types covered by the vaccine [18]. The "Guidelines for Comprehensive Prevention and Control of Cervical Cancer (2nd Edition)" of the Women's Health Branch of the Chinese Preventive Medicine Association stated: "HPV vaccination will achieve the best preventive effect in women who have not had sexual intercourse; but for women who have already had sexual intercourse, research experiments have shown that HPV vaccination also has a good protective effect [3]."

Can little girls be vaccinated? HPV vaccination before the first sexual intercourse can have a better preventive effect for girls of appropriate age[19][20]: Before sexual intercourse begins, the chance of HPV infection is lower, and HPV vaccine is more effective in protecting uninfected people, so vaccination before infection can be more effective in preventing HPV[19][20]. Young age can easily stimulate a better immune response, helping adolescent girls get better protection[21-25]. Therefore, WHO recommends that girls aged 9-14 who have not had sexual intercourse should be the first to be vaccinated[26].

No matter what age we are, it is very necessary for us to prevent HPV infection in advance. After all, health comes first. Protecting your cervical health will make you and your family feel more at ease and give you more confidence to unlock the infinite possibilities of future life!

References:

1. Vaccine and Immunity Branch of Chinese Preventive Medicine Association. Expert consensus on immune prevention of human papillomavirus-related diseases such as cervical cancer [J]. Chinese Journal of Preventive Medicine, 2019, 53(8): 761-803.

2. Qiao Youlin. Current status of epidemiological research on human papillomavirus infection and cervical cancer in Chinese women and prospects for vaccine prevention [J]. Chinese Journal of Epidemiology, 2007, 28(10): 937-940.

3. Wang Linhong, Zhao Gengli. Comprehensive prevention and control guidelines for cervical cancer (1st edition) [M]. Beijing: People's Medical Publishing House. 2017.8

4. Healthy Hangzhou. http://www.hangzhou.gov.cn/art/2022/3/1/art_1228974667_59050840.html.

5. CDC. Genital HPV Infection – Basic Fact Sheet. https://www.cdc.gov/std/hpv/stdfact-hpv.htm#print.

6. Human Papillomavirus: A Hidden Epidemic in the United States. https://www.prb.org/resources/human-papillomavirus-a-hidden-epidemic-in-the-united-states/.

7. CDC Fact Sheet_Genital HPV Infection: https://www.cdc.gov/std/hpv/hpv-Fs-July-2017.pdf.

8. Walboomers JM, Jacobs MV, Manos MM, Bosch FX, Kummer JA, Shah KV, Snijders PJ, Peto J, Meijer CJ, Muñoz N. Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J Pathol. 1999 Sep;189(1):12-9.

9. Gravitt PE. The known unknowns of HPV natural history. J Clin Invest. 2011 Dec;121(12):4593-9. doi: 10.1172/JCI57149. Epub 2011 Dec 1.

10. Muñoz, Nubia, et al. "Epidemiologic classification of human papillomavirus types associated with cervical cancer." New England journal of medicine 348.6 (2003): 518-527.

11. Bruni L, et al. ICO/IARC Information Center on HPV and Cancer (HPV Information Centre). Human Papillomavirus and Related Diseases in China. Summary Report 10 March 2023.

12. Bruni L, et al. ICO/IARC Information Center on HPV and Cancer (HPV Information Centre). Human Papillomavirus and Related Diseases in the World. Summary Report 10 March 2023.

13. Li K, Li Q, Song L, Wang D, Yin R. The distribution and prevalence of human papillomavirus in women in mainland China. Cancer. 2019 Apr 1;125(7):1030-1037.

a. Study design: A Chinese systematic review of 198 studies was conducted, using PubMed, Web of Science, Medline (Ovid), CNKI and Wanfang databases to search for epidemiological studies on high-risk human papillomavirus in women in mainland China published from January 2000 to June 2018. A total of 3,177,080 general female population (women with symptomatic outpatient clinics or health examinations) and 85,743 women with cervical lesions (including 24,925 women with cervical cancer) were included to evaluate the epidemiology of high-risk HPV infection in women in mainland China.

Results: The overall infection rate of high-risk HPV in the general female population in mainland China was 19.0% (95% CI, 17.1%-20.9%), and the top five subtypes with the highest infection rates were 16, 52, 58, 53, and 18. The infection rate among symptomatic outpatients was 25.7% (95% CI, 22.2%-29.2%), and the infection rate among healthy women undergoing physical examinations or routine cervical cancer screening was 12.9% (95% CI, 11.7%-14.1%). The infection rates of high-risk HPV in the general female population aged <25 years, 25-45 years, and >45 years were 24.3% (95% CI, 19.0%-29.6%), 19.9% ​​(95% CI, 16.4%-23.4%), and 21.4% (95% CI, 17.3%-25.5%), respectively.

14. Chinese Preventive Medicine Association Women's Health Branch. Comprehensive Prevention and Control Guidelines for Cervical Cancer (2nd Edition)[M]. Beijing: People's Medical Publishing House. 2023

15. Zhang Jingfei, Wang Tong, Wu Minghui, et al. Epidemiological status and clinical characteristics of 1399 cases of cervical cancer in Beijing. Chinese Medical Journal. 2011;91(43):3058-3061.

b. Research design: A stratified cluster sampling method was used to select 2 tertiary specialized hospitals, 10 general tertiary hospitals, and 10 suburban secondary hospitals in Beijing. A total of 1399 medical records of cervical invasive pain from 1990 to 2009 were retrospectively investigated. The years were divided into 4 groups according to 5 years, and the clinical characteristics of each group were statistically analyzed. Research results: (1) The number of new cases of cervical cancer has been increasing in the past 20 years. (2) Age: 17-88 years old, the average age decreased from 58.2 years to 46.0 years old, and the difference was statistically significant (P < 0.01); stage: stage I 772 cases (57.1%), stage II 380 cases (28.1%), stage III 182 cases (13.5%), stage IV 18 cases (1.3%), the proportion of stage I and stage II increased from 69.6% (16/23) to 89.4% (530/856) year by year. Pathology: There were 1135 cases of squamous cell carcinoma (83.1%) and 182 cases of adenocarcinoma (13.3%). There was no significant change in the pathological type over the past 20 years, and squamous cell carcinoma was still the main type (P＞0.05).

16. Wang Panpan, Liu Lei, Zhu Li. Research progress on human papillomavirus vaccine and cervical cancer screening in the vaccine era[J]. Chinese Journal of Postgraduate Medical Education, 2019, 42(4): 369-372.

17. Wu EQ, et al. Prevalence of type-specific human papillomavirus and pap results in Chinese women: a multi-center, population-based cross-sectional study. Cancer Causes Control. 2013 Apr;24(4):795-803.

c. Study design: A multicenter, population-based study conducted in China from 2006 to 2007. HPV testing data of cervical exfoliated cells from 4215 women aged 17-54 years in five regions were collected to assess the disease burden of HPV infection in sexually active women in China. Results: The prevalence of HPV was 14.3%. The most common types were HPV16 (2.9%), HPV52 (1.7%), HPV58 (1.5%), HPV33 (1%), and HPV18 (0.8%).

18. Wei Lihui, Qiao Youlin. 100 Questions and Answers on Preventing Cervical Cancer[M]. Beijing: People's Medical Publishing House. 2018

19. Human papillomavirus vaccines: WHO position paper, October 2014. Wkly Epidemiol Rec. 2014 Oct 24;89(43):465-91. English, French. PMID: 25346960.

20. Schiller JT, Castellsagué X, Garland SM. A review of clinical trials of human papillomavirus prophylactic vaccines. Vaccine. 2012 Nov 20;30 Suppl 5(0 5):F123-38.

21. Chinese Society of Gynecologic Oncology, Chinese Society of Eugenics, Colposcopy and Cervical Pathology, Martin, et al. Chinese expert consensus on the clinical application of human papillomavirus vaccine[J]. Journal of Peking Union Medical College, 2021, 12(2): 189-201.

22. Zhu F, Li J, Hu Y, et al. Immunogenicity and safety of the HPV-16/18 AS04-adjuvanted vaccine in healthy Chinese girls and women aged 9 to 45 years. Hum Vaccin Immunother. 2014;10(7):1795-1806. doi:10.4161/hv.28702

23. Li R, Li Y, Radley D, et al. Safety and immunogenicity of a vaccine targeting human papillomavirus types 6, 11, 16 and 18: a randomized, double-blind, placebo-controlled trial in Chinese males and females. Vaccine. 2012;30(28):4284-4291.

24. Hu YM, Guo M, Li CG, et al. Immunogenicity nonin -feriority study of 2 doses and 3 doses of an Escherichia coliproduced HPV bivalent vaccine in girls vs. 3 doses in young women [J]. Sci China Life Sci, 2020, 63: 582-591

25. Lei JY, Ploner A, Elstrom KM, et al. PV Vaccination and the Risk of Invasive CervicalCancer [J]. N Engl J Med, 2020, 383: 1340-1348

26. Human papillomavirus vaccines: WHO position paper, December, 2022: https://www.who.int/publications/i/item/who-wer9750-645-672.