the anus and rectum due to their fragility. Unprotected penile-anal penetration, colloquially known as barebacking, carries a higher risk of passing on sexually transmitted infections (STIs) because the anal sphincter is a delicate, easily torn tissue that can provide an entry for pathogens. Use of condoms, ample lubrication to reduce the risk of tearing, and safer sex practices in general, reduce the risk of STIs. However, a condom can break or otherwise come off during anal sex, and this is more likely to happen with anal sex than with other sex acts because of the tightness of the anal sphincters during friction. Unprotected receptive anal sex (with an HIV positive partner) is the sex act most likely to result in HIV transmission. Other infections that can be transmitted by unprotected anal sex are human papillomavirus (HPV) (which can increase risk of anal cancer); typhoid fever; amoebiasis; chlamydia; cryptosporidiosis; E. coli infections; giardiasis; gonorrhea; hepatitis A; hepatitis B; hepatitis C; herpes simplex; Kaposi's sarcoma-associated herpesvirus (HHV-8); lymphogranuloma venereum; Mycoplasma hominis; Mycoplasma genitalium; pubic lice; salmonellosis; shigella; syphilis; tuberculosis; and Ureaplasma urealyticum. As with other sexual practices, people without sound knowledge about the sexual risks involved are susceptible to STIs. Because of the view that anal sex is not "real sex" and therefore does not result in virginity loss, or pregnancy, teenagers and other young people may consider vaginal intercourse riskier than anal intercourse and believe that a STI can only result from vaginal intercourse. It may be because of these views that condom use with anal sex is often reported to be low and inconsistent across all groups in various countries. Although anal sex alone does not lead to pregnancy, pregnancy can still occur with anal sex or other forms of sexual activity if the penis is near the vagina (such as during intercrural sex or other genital-genital rubbing) and its sperm is deposited near the vagina's entrance and travels along the vagina's lubricating fluids; the risk of pregnancy can also occur without the penis being near the vagina because sperm may be transported to the vaginal opening by the vagina coming in contact with fingers or other non-genital body parts that have come in contact with semen. There are a variety of factors that make male-to-female anal intercourse riskier than vaginal intercourse for women, including the risk of HIV transmission being higher for anal intercourse than for vaginal intercourse. The