(May 2001) The human papillomavirus is the most common sexually transmitted infection (STI) in the United States, with an estimated 24 million active cases and 5.5 million new cases each year, according to the National Cancer Institute. Various strains of HPV cause the great majority of cases of cervical cancer. Despite this fact, public ignorance about HPV is high. Recent studies have shown that there are high levels of HPV infection among women, with the highest levels among young women, according to the U.S. Centers for Disease Control and Prevention (CDC). One recent study among female college students indicated that an average of 14 percent become infected with genital HPV each year. Levels of current infection in men of the same age appear to be similar.
According to the Kaiser Family Foundation, 70 percent of American adults 18 and older have never heard of HPV. Furthermore, most (89 percent) have never discussed the issue with their health provider. Although cases of HPV are not formally reported in the United States, available data from the CDC indicate that at least 75 percent of the reproductive-age population has been exposed to the sexually transmitted HPV. Fifteen percent of Americans ages 15 to 49 are estimated to be infected. Risk factors of infection include lifetime multiple sex partners, history of infection with other sexually transmitted infections (STIs), early age at first intercourse, a weakened immune system, and the presence of HIV.
HPV is typically spread by direct, skin-to-skin contact during vaginal, anal, or oral sex with someone who has the infection. Despite their potential severity, the health consequences of HPV (and other STIs) often are hidden and can occur years after infection. Thus, many people do not know that they are infected or that they can pass the virus on to others.
Vietnamese Women Have the Highest Incidence of Invasive Cervical Cancer in the United States
Cervical cancer, which is associated with HPV infection, is now the ninth most common cancer among women in the United States. According to the American Cancer Society, in 1999, nearly 12,800 cases of this type of cancer were diagnosed. Of these cases, about one-third will ultimately die of the disease.
In the United States, Vietnamese women have the highest incidence of invasive cervical cancer (43 per 100,000); this probably reflects the lack of prior screening with a Pap smear, which can detect cervical cancer at an early treatable phase. Alaska Native, Korean, and Hispanic women represent other at-risk populations, with incidence rates of 15 per 100,000 or higher. African American women are more than twice as likely to die from the disease (6.7 per 100,000) than their white counterparts (2.5 per 100,000). This is due to the high number of cervical cancer deaths among older African American women, according to the National Cancer Institute. Women ages 65 and older, particularly African Americans, have much lower screening rates than their younger counterparts.
Prevention and Controversy: From Pap Smears to Politics
There is no effective way to prevent HPV infection. While condoms can reduce the risks, the virus can still be transmitted through even minor cuts in the skin. According to Penny Hitchcock, chief of the Sexually Transmitted Diseases Branch of the U.S. government's National Division of Microbiology and Infectious Diseases, further research on topical microbicides and effective vaccines is critical. In addition, she strongly encourages young women to obtain regular Pap smears to help monitor the possible presence of pre-cancerous lesions that could lead to invasive cervical cancer.
Controversy exists about how best to handle the issue of HPV. One former U.S. legislator, Rep. Tom Coburn, R-Okla., has argued that several steps need to be taken to reduce the incidence of HPV. These include reporting new cases of HPV to the CDC and placing warnings on condom packages that condoms do not protect against HPV and that the virus is connected to cervical cancer. Many public health experts believe that a more targeted public health and research effort would have greater impact. This response involves encouraging greater sex education in schools and by health professionals regarding HPV and other STIs, promoting more regular Pap smears, and using HPV DNA testing.
The U.S. Food and Drug Administration have approved one HPV DNA test for use as a follow-up to irregular Pap smears. The test, which detects HPV on the cervix through administration of a cervical swab done by a health provider, distinguishes between high- and low-risk types of HPV.
A new vaccine against the most common strains of HPV may also be able to protect against 80 percent of cervical cancers. The vaccine, developed by a Johns Hopkins University researcher, produced a strong immune response against HPV when tested on more than 70 volunteers. This vaccine may hold particular promise for less developed countries, where rates of cervical cancer are higher because women cannot afford Pap tests to detect the disease.
It is also imperative to continue using condoms. Condoms, particularly when used with spermicidal foams, creams, and jellies, may reduce the risk of transmitting HPV and other STIs for those who are sexually active. Sexual abstinence is another option.
The Magnitude of the STI Epidemic in the United States
In addition to HPV, there are other diseases that are spread primarily through sexual activity. Taken together, they represent a significant public health problem in the United States. According to the latest CDC estimates, more than 65 million people in the country currently live with an incurable STI. Of these, 20 million Americans carry HPV. In addition, researcher Willard Cates estimates that there are 15 million new STI cases in the United States each year. Genital HPV represents one-third of all new STI infections each year. About one-fourth of these infections occur in adolescents. Even though some of the STIs, such as syphilis, are declining, others, like gonorrhea, chlamydia, and genital herpes persist in the population.
According to a speech given Dr. Judith Wasserheit, director of the STD Prevention Program at the CDC, gonorrhea represents one of the key diseases for American youth. Gonorrhea is a curable bacterial disease that if left untreated can cause pelvic inflammatory disease and infertility in women. Those infected with gonorrhea also face greater risk of transmitting or becoming infected with the AIDS virus.
Gonococcal infections rose 9 percent from 1997 to 1999, especially among young people, gay and bisexual men, and African Americans. While 360,000 new cases are reported each year, Wasserheit believes that the actual numbers are twice as high. The Southern states are the most heavily affected. Poverty and inadequate access to quality health care and preventive services are primary reasons for the increase. Being infected with gonorrhea can cause pelvic inflammatory disease (PID) and infertility if untreated in women. It can also raise the risk of transmitting or becoming infected with HIV/AIDS.
Chlamydia is the most common bacterial STI in the United States. If left untreated, 20 percent to 40 percent of women with genital chlamydial infections develop PID, which can lead to infertility, ectopic pregnancy, and chronic pelvic pain. Recent studies have also linked chlamydia with increased risk of developing cervical cancer.
More than one in five Americans is infected with genital herpes. The prevalence of herpes simplex virus type two (the virus that causes genital herpes) has remained relatively stable at 19 percent among youth, according to the CDC.
American Cancer Society, "Cancer Facts and Figures" (2000).
American Social Health Association, "Sexually Transmitted Diseases in America: How Many Cases and At What Cost?" (December 1998).
W. Cates et al., "Estimates of the Incidence and Prevalence of Sexually Transmitted Diseases in the United States," in Sexually Transmitted Diseases, 1999.
Couto Ilka and Cynthia Dailard, "Wanted: A Balanced Policy and Program Response to HPV and Cervical Cancer," in the Guttmacher Report on Public Policy, December 1999.
Kaiser Family Foundation, "HPV and Cervical Cancer" Fact Sheet, February 2000.
U.S. Centers for Disease Control and Prevention, "Tracking the Hidden Epidemics: Trends in STDs in the United States," 2000.
Table 1: Incidence/Prevalence of STIs in the US
||Incidence (Estimated number of new cases every year)
||Prevalence* (Estimated number of people currently infected)
|Human papillomavirus (HPV)
* No recent surveys on national prevalence for gonorrhea, syphilis, trichomoniasis, or bacterial vaginosis have been conducted.
** Bacterial vaginosis is a non-sexually transmitted genital infection that causes most vaginal symptoms among women of childbearing age.
Sources: Kaiser Family Foundation, "HPV and Cervical Cancer" Fact Sheet (February 2000); American Social Health Association, "Sexually Transmitted Diseases in America: How Many Cases and at What Cost?" (December 1998); U.S. Centers for Disease Control and Prevention, "Tracking the Hidden Epidemics: Trends in STDs in the United States" (2000); and W. Cates et al., "Estimates of the Incidence and Prevalence of Sexually Transmitted Diseases in the United States," in Sexually Transmitted Diseases, 1999.
What is HPV?
HPV is the name of a group of more than 100 types of viruses. Thirty of these viruses are sexually transmissible and constitute genital HPV. There is debate about whether some strains of HPV are transient infections that may be cleared from the body, or whether these strains of HPV permanently reside there but may be difficult to detect at times. Other types of HPV can cause visible, and sometimes troublesome, genital warts. Research also shows that a small number of more persistent HPV strains may lead to cervical cancer. HPV has no cure but symptoms (including genital warts and early stages of cervical cancer) can be treated.
Measures of STIs
Estimates of the incidence and prevalence of STIs, including HPV, in the U.S. vary according to the source of data and the methods used to detect infections. Sources include reportable infections to the CDC such as gonorrhea, syphilis, and chlamydia; diagnoses made during visits to office-based health practitioners; national surveys of representative populations; prevalence data for those attending special health facilities such as family planning clinics; and data from other national STI surveys such as the National Disease and Therapeutic Index. There is no national reporting requirement for the other five major STIs — genital herpes, HPV, hepatitis B, HIV, and trichomoniasis.
Steps Taken by CDC to Address HPV
In response to the HPV situation, the U.S. Congress in the 2001 appropriations bill required CDC to conduct further research and activities regarding HPV. Over the next few years, CDC will
- carry out a study to determine the incidence of HPV infection in adolescent girls aged 12–19 years of age in Atlanta;
- establish additional HPV prevalence and epidemiology surveillance in nationally representative samples using the National Health and Nutrition Examination Survey with special focus on HPV 16, the most common "high risk" type of HPV associated with cervical cancer;
- establish four to eight sentinel surveillance sites to monitor the prevalence of high-risk HPV types in women;
- implement a research and patient survey to develop and pilot health messages for HPV patients and their partners;
- conduct a survey of health providers to assess knowledge, attitudes, and practices regarding HPV diagnosis and treatment to improve testing, treatment, and counseling of HPV patients and their partners.
For More Information
More information about STIs in the U.S. and Canada, including HPV, can be found on these websites:
CDC's Division of Sexually Transmitted Disease Prevention www.cdc.gov/std/
American Social Health Association www.ashastd.org
Health Canada www.hc-sc.gc.ca/
Joan R. Cates, MPH, vice-president for development and policy, American Social Health Association, Dr. Thomas Wong, chief, STD Prevention and Control, Health Canada, and Dr. Robert Semenciw, statistician, Centre for Chronic Disease Prevention and Control, Health Canada, provided valuable advice and review for this article. Liz Creel is a population specialist at PRB.