HIV might still be the most feared se_xually transmitted disease, but it’s not necessarily the easiest to contract. Human papillomavi_rus is one of the leading killers of humans worldwide—and a condom is only 60 percent effective at stopping it.

The disease is believed to have already killed thousands in Limpopo, South Africa.

If s_ex education classes have managed to teach anyone anything, it’s the power of the condom. Co_ndoms are supposed to make s_ex safe—from pregnancy, from HIV, and from a host of other se_xually transmitted infections.

Co_ndoms have one huge weakness that often gets overlooked: they can’t fully protect against the Human papillomavirus, better known as HPV. It doesn’t sound pretty, it doesn’t look pretty, and especially for women, HPV is a silent killer that can lie dormant for years unnoticed before it strikes, Imzansi reports.

The HPV Nightmare

HPV is the most commonly transmitted STI in the United States. It’s actually a catch-all category for nearly 150 strains of similar viruses, many of which cause nasty looking warts.

A Prolific Virus

HPV is so common, almost all se_xually active men and women contract it at some point in their lives. The virus is spread by intimate skin-to-skin contact, meaning that anywhere two bodies touch, HPV can be spread—which makes co_ndoms only somewhat effective in preventing it.

HPV can be passed from person to person, even when the infected individual has no signs or symptoms of the virus. It can take years for any symptoms to show up after being infected with HPV, and some people never experience any symptoms at all.

Ties to Cancer

HPV is none too pretty to look at, but for women especially, the virus can prove deadly. It’s closely tied with cervical cancer, which is a leading killer of women. Two types of the virus, HPV types 16 and 18, account for nearly 70% of all cervical cancer cases.

Danger to Women

Women are also at a much higher risk of contracting the virus than men. Male-to-female transmission has a 5% higher rate of occurrence than female-to-male transmission.

Absolute Prevention

It can be nearly impossible to tell whether or not a se_xual partner has been infected with HPV. The only way to be 100% sure you don’t get the virus is to maintain complete abstinence—which means no kissing or even touching of anyone’s no-no parts.