Human papillomavirus is a sexually transmitted virus that can cause cervical cancer. There are more than 30 different varieties of HPV that are sexually transmitted, though they are similar in some ways. Most women with HPV—which is actually nearly ubiquitous among sexually active people—will never develop cervical cancer, but almost every case of cervical cancer is a result of infection with HPV.
In fact, most women with HPV will never show symptoms at all, especially if they have one of the types that can lead to cervical cancer. That is why it’s important for a woman to get regular tests for the presence of HPV once she is sexually active, especially if she has not been vaccinated. Vaccination protects against the types that cause most cases of cervical cancer—type 16 and type 18, together responsible for more than two-thirds of HPV-related cancers—bot not the other types, which cause warts or nothing at all.
The screening test was developed by a Greek-born doctor, Georgios Papanikolaou, in America in 1928; the name is typically shortened to "Pap test." It is ordinarily painless if done correctly. The Pap test is performed by collecting cells from the cervix, depositing them onto a microscope slide, and dyeing them so that the cells are visible. In modern labs, the slides are initially examined by a computer, which is programmed to detect abnormalities. If a slide seems to have indicators of HPV infection, it is looked at by a doctor. If the doctor confirms the indications, a specific test is then performed to look for the virus directly.
Pap smears are generally not recommended for people under 21, because testing below that age has not been found to lead to reductions in the cancer rate, or for people who have never been sexually active, because that is the only way the cancer-causing virus is transmitted. However, people under 25 who show signs of possible HPV infection should be screened. Vaccinations, which are available for both men and women and can be given to children before they become sexually active, provide a significant amount of protection, but regular testing is still needed.