Girls, boys, young men and women, parents: the HPV vaccine helps to prevent cervical, anal, penile, vulvar, throat and esophageal cancers.

The news Wednesday that former "Desperate Housewives" actress Marcia Cross may have gotten anal cancer from the human papillomavirus and her husband who had throat cancer about a decade ago, provides a Hollywood health lesson on the importance of the controversial HPV vaccine.

Here's what you need to know:

Q: How common is HPV?

A: HPV is very common and nearly everyone who is sexually active and doesn't get the vaccine will get infected with it at some point in their lives, says the Centers for Disease Control and Prevention. It's the most common sexually transmitted disease in the world, but it can also be spread skin-to-skin. Nearly 80 million Americans — most in their late teens and early 20s — have HPV, the CDC says.

Q: What's the link between HPV, warts and cancer?

A: HPV can lead to cancer, but the infections usually go away by themselves. About 10 to 20% of people who aren't vaccinated against it, have HPV, DC says. The vaccination can also prevent genital warts, which CDC says do not lead to cancer. Low-risk types of HPV can cause warts, while the high risk types can cause cancers. More than 90% of anal cancers are caused by HPV.

Dr. Benigno Varela, a gastroenterologist with the Gastroenterology Center of CT, says the strains of HPV that lead to anal warts are different than the ones linked to anal cancer, but "patients who do have anal warts are more likely to also have the (HPV) strains that lead to anal cancer." Vaginal, genital and anal warts are also so close in proximity that people are likely to have been exposed all strains of HPV, he says.

Q: Isn't the HPV vaccine for young girls to prevent cervical cancer?

The CDC recommends the vaccine for girls and young women age 11 to age 26 and males 11 to 21. It protects against cervical cancer as well as other cancers that can affect men.

Q: I'm a one-partner woman (or man). Why do I need the vaccine?

A: Even monogamous married couples can pass HPV to each other contracted years or decades earlier. Cross told CBS This Morning on Wednesday that doctors suspect her cancer and her husband Tom Mahoney's throat cancer came from the same type of HPV. It can be transferred through vaginal or anal intercourse, oral sex or other skin-to-skin contact. Condoms are about 70% effective in preventing the spread, the CDC says.

Read more:Marcia Cross wants to destigmatize anal cancer, says hers was linked to husband's battle

Q: You don't hear much about anal cancer? Why?

A: It's extremely rare and it's also down there. Cross told CBS This Morning that it was hard for her to even say the word "anal" or "anus" until recently. Besides, it wasn't too long ago that women didn't even talk about having breast cancer. The American Cancer Society estimates there will be 8,580 new cases of anal cancer in the U.S., including 5,620 in women and 2,960 in men. An estimated 1,160 of these people will die. Almost all cases of anal cancer are in people 35 years of age or older.

Anal cancer may be rare, but Dr. Patrick Boland, a medical oncologist with Buffalo-based Roswell Park Comprehensive Cancer Center, says he's seen several patients with new diagnoses in the last two weeks alone.

Q: How would I know if I had anal cancer?

A: Most cases of anal cancer are caught early because of anal bleeding or tenderness and pain. After all, there are a lot of nerve endings in the region, notes Boland. But CDC says HPV and anal cancer generally do not cause symptoms in the very early stages. Other symptoms include warts that itch or bleed in the anal canal or a hard lump that appears to increase in size, says the CDC.

Q: What should I do if I'm worried I might have anal cancer?

A: There are no strict guidelines currently for screening for anal HPV, says Varela. Those with HIV — even if they are on antiretroviral drugs, which don't reduce the risk of anal cancer — should consider being screened, he says. So should men who have sex with men, women who have had HPV or HPV-related warts or cervical dysplasia and anyone with anal warts be screened for anal cancer, Varela says.

Prevention, however, is the place to start.

"The biggest thing as a society we can do is impress about the importance of HPV vaccination," says Boland. "This is a preventive cancer vaccine so I'm glad it’s in the news to spread awareness."