Cervical cancer is a type of cancer that occurs in the cervix. The cervix connects the lower part of a woman’s uterus to her vagina. Cervical cancer was once a leading cause of death among U.S. women. That changed when the Pap smear became widely available. This test allows doctors to find precancerous changes in a woman’s cervix and treat them. According to the American Cancer Society (ACS), the mortality rate has declined by 50 percent within the last 40 years.

The ACS estimates that in 2017, approximately 12,820 American women will be diagnosed with cervical cancer and 4,210 will die from the disease. Most instances will be diagnosed in women who are between the ages of 20 and 50.

The uterine cervix is also known as “the mouth of the womb.” If you’re a woman, it’s the hollow cylinder that connects your uterus to your vagina. Your uterus is where a fetus grows during a pregnancy.

The surface of your cervix faces outward into your vagina. It’s made up of types of cells different from the lining of your cervical canal. Most cervical cancers start on the surface of the cervix.

Almost all cervical cancers are caused by the sexually transmitted human papillomavirus (HPV). There are a number of different strains of HPV. Only certain types are associated with cervical cancer. The two types that most commonly cause cancer are HPV-16 and HPV-18.

Infection with a cancer-causing strain of HPV doesn’t mean you’ll get cervical cancer. Your immune system eliminates the vast majority of HPV infections. Most people are rid of the virus within two years. However, HPV is extremely common. The Centers for Disease Control and Prevention estimates that most sexually active men and women will become infected by HPV during their lifetime.

HPV can also cause other cancers in women and men. These include:

However, infection from the two most common cancer-causing strains of HPV is preventable by vaccine. Vaccination is most effective before a person becomes sexually active. Both boys and girls can be vaccinated against HPV.

The risk of HPV transmission can also be reduced by practicing safe sex. However, condoms can’t prevent all HPV infections. The virus can also be transmitted from skin to skin.

A Pap smear is a test doctors use to diagnose cervical cancer. To perform this test, your doctor collects cells from the surface of your cervix. These cells are then sent to a lab to be examined under a microscope for evidence of precancerous or cancerous changes. If such changes are found, your doctor may suggest a colposcopy, a procedure for examining your cervix. Early lesions can be removed before they cause too much damage.

Routine Pap smears have greatly reduced the number of deaths from cervical cancer.

The five-year survival rates for cervical cancers that are caught early are excellent. This isn’t the case for larger, invasive cancers. When the cancer has spread, or metastasized, within the pelvic region, the five-year survival rate drops to 57 percent. If the cancer spreads beyond this area, the rate drops to 16 percent, according to the ACS.

Routine Pap smears are important. Caught early, cervical cancer is very treatable. Precancerous changes are often detected and treated before cervical cancer can develop. Testing and treatment stops cervical cancer before it starts. According to the ACS, the majority of American women who are diagnosed with cervical cancer have either never had a Pap smear or not had one in the last five years.