About 26,000 cases of cancer diagnosed in the U.S. each year are caused by infection with the human papillomavirus (HPV), according to a new government report.
Of these cases, 18,000 occur in females and 8,000 occur in males, according to researchers from the Centers for Disease Control and Prevention. The most common of these cancers was cervical cancer, with 11, 500 yearly cases, on average, attributable to HPV infection. There are also 7,400 cases of oropharyngeal cancer (which occurs in the mouth or throat), 4,500 cases of anal cancer, 1,600 cases of vulvar cancer, 500 cases of vaginal cancer and 400 cases of penile cancer that are due to the virus.
Most HPV infections clear within a year or two, but those that persist can progress to cancer, according to the report.
Transmission of HPV can be reduced through condom use and limiting the number of sexual partners, according to the report. Cervical cancer can be prevented with HPV vaccinations and early screening for the disease.
The report is based on an analysis of data reported in 2004 through 2008 to the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute.
The data showed that on average, 33,369 cases of cancer were diagnosed every year at sites in the body where HPV-related cancers are known to occur. Previous studies, in which researchers looked at the DNA of cancer cells, have yielded information about the percentages of cancer cases occurring at a given site in the body that are, in fact, caused by HPV. For the new report, the CDC researchers took these percentages into account when calculating the number of HPV-related cancers that are actually caused by HPV.
Two vaccines are available to protect against HPV 16 and 18, the strains that cause most cancers. The CDC's Advisory Committee on Immunization Practice recommends routine vaccination of girls ages 11 or 12 with three doses of either vaccine, and routine vaccination of boys at ages 11 or 12 with three doses of the Gardasil vaccine, which also offers protection against HPV 6 and 11, the strains linked with genital warts.
One previous study of HPV transmission found that if one person in a heterosexual couple has HPV, there's a 20 percent chance his or her partner will pick up the virus within six months.