Dr. Javier Del Pozo Roselló,

Approximately 20 million people are currently infected by HPV. It is the most common sexually transmitted virus. Most infections are transitory and asymptomatic and disappear after 12 or 18 months. At least 80% of women will have contracted an HPV genital infection by the time they are 50.

Early detection of infection by the human papillomavirus (HPV) by changes in cervico-vaginal cytology (Papanicolaou tests) is effective in reducing the incidence of cervical cancer.

Mainly by genital contact. Most HPV infections present neither signs nor symptoms; that is why most people who have the infection do not even realise it, although they can transmit the virus to their sexual partner.

Most people who have genital HPV infections do not know that they are infected. The "low-risk" types of virus cause visible genital warts or present precancerous changes in the uterine cervix, vulva, anus or penis.

Genital warts generally appear as pinkish or skin-coloured excrescences or wettish lumps, usually in the genital area. The warts may be flat or raised, single or multiple, large or small, and in certain cases may assume the shape of a cauliflower.

Genital warts can be diagnosed by a visual examination and can be eliminated with medication, although there is no one treatment that is better than another.

When the lesions are not apparent, they can mainly be diagnosed by Papanicolaou tests (Pap smears). Specific tests also exist for detecting HPV that can be performed in women giving slightly abnormal results for the the Papanicolaou test, or in those older than 30 when taking the Papanicolaou test. There are no tests for detecting HPV in men.

There is no "cure" as such for HPV, although in most women the infection disappears on its own.

The Papanicolau test is able to detect cancerous and precancerous cells in the uterine cervix. Regular Papanicolaou tests and careful medical monitoring, with treatment if required, can help to ensure that any precancerous changes in the uterine cervix caused by HPV infection do not develop into cervical cancer, which is potentially fatal.

The safest way is to avoid genital contact with another person. If people decide to be sexually active, the best strategy is a stable monogamous relationship with a medically tested, uninfected partner. HPV is so widespread that only those people who have had no sexual relations can be sure that they have not been exposed to it.

People who decide to be sexually active and are not in a long-term, mutually monogamous relationship can reduce their risk of infection by limiting their number of sexual partners, and by choosing one who has previously had few or no sexual partners in the past.

HPV infection can appear in both male and female genital areas, whether or not they are or have been covered or protected by a latex condom.

Condylomata acuminata or venereal warts are caused by some types of HPV. They are transmitted sexually and appear within 3 months after contact with an infected partner. In women, they appear in the labia of the vulva, vagina, uterine cervix or around the anus. In men, they appear on the penis and the scrotum, or around the anus if the patient has homosexual relations.

• Quadrivalent vaccine: recently approved by the USA Food and Drug Administration (FDA). It gives protection against four types of HPV: 6, 11, 16 and 18. It is administered in three injections over a period of 6 months.
• Bivalent vaccine: still undergoing trials; protects against two types of HPV: 16 and 18. It is also administered in three doses over a 6-month period. Both vaccines are based on a technology partly developed by scientists from the National Cancer Institute (NCI).

They work like other vaccines that protect against a viral infection. The unique surface components of HPV can create an antibody response capable of protecting the body against infection, and these components can be used as a basis for developing a vaccine.

They are extremely effective for preventing infection by the specific types of HPV for which they have been devised. The vaccine approved by the FDA (Food and Drug Administration) provided protection against almost 100% of the precancerous changes in cervical cells caused by these types of HPV, up to a period of 4 years after vaccination.

They are potentially capable of reducing the number of deaths from cervical cancer worldwide by two thirds. Furthermore, these vaccines can obviate the need for medical care, biopsies and invasive measures associated with follow-up procedures after abnormal results for the Papanicolaou test.

Before authorizing any vaccine, the FDA must verify that it is both effective and safe. These vaccines have been tested on thousands of people in the USA and many other countries. No serious secondary effects have been reported to date. The most common problem is a brief pain in the injected area and other symptoms normally associated with other approved vaccines.

This remains to be determined. To date, however, they are known to provide protection against HPV 16 for up to 4 years. Research on vaccines currently undergoing trials shows that they provide protection against infection by HPV 16 and 18 for more than 4 years.

Trials are being carried out to determine the necessity of booster shots (complementary doses of a vaccine, usually weaker than the first dose, that are given to maintain immunity).

Vaccines are only effective if they are given prior to HPV infection; it is advisable to administer them before the individual becomes sexually active. The FDA approved this vaccine for females between the ages of 9 and 26 years.

The preventive vaccines currently being researched do not treat infections, although in general they have been proved to be safe when administered to women already infected by HPV. At present, there is in general no examination available to check if a person has been exposed to HPV; it only shows whether a women has an HPV infection and identifies the HPV type. It provides no information about past infections. The decision whether or not to administer the vaccine on the basis of possible previous exposure to these types of HPV is currently being discussed by the Advisory Committee on Immunization Practices and by other advisory bodies.

The vaccine appears to be safe in women who present cervical abnormalities, but it is not known if the vaccine can help to remedy such abnormalities. Women should speak to their doctors about treatment for any abnormal changes in their cervical cells.

Given that the vaccine does not provide protection against all types of HPV, Papanicolaou tests and selective detection examinations are still essential for identifying cervical cancer and precancerous changes.