HPV Modes of Transmission - An Overview

Introduction:

The issue of transferring HPV between the mouth and genitals is rarely explored in research because it involves very personal matters. Also, little information is available about how the body clears HPV from the upper airways. A lot of cancers in the head and neck, especially in the throat, are caused by HPV. The rise in HPV-related cancers might be because of changes in sexual behaviors, but the understanding of how HPV gets into the mouth is still incomplete.

Many sexually active people get HPV at some point without knowing it because it does not always cause symptoms. How likely someone is to get HPV and how long they have it depends on things like their sexual activity, the amount of virus in their body, where it is located, their immune system, and how well their body clears the virus. As people get older, they are less likely to get new HPV infections but more likely to keep the virus they already have, maybe because of changes in sexual habits or how their immune system works as they age.

What Is HPV Infection?

Human papillomaviruses (HPVs) are viruses that do not have an outer coating and carry genetic material. There are over 200 kinds of HPVs. All types of HPV are attracted to and infect the squamous epithelial cells found in the skin and mucous membranes. HPV infections are very common. This infection is the most common sexually transmitted infection for both men and women. HPV infections usually do not show any symptoms and often go unnoticed.

What Are the Different Modes of Transmission for Human Papillomavirus Infection?

The human papillomavirus virus spreads when there is direct contact with the skin or mucosa where HPV warts are present. Being around someone with the virus is not usually enough to cause a problem. But if rubbing or friction causes tiny cuts, the virus can get through the skin. That is why sexual activity (like vaginal or anal sex) is the main way HPV spreads. Other types of sexual activity (like touching genitals with hands, skin-to-skin contact without penetration, oral sex, or sharing sex toys) can also lead to problems if there are cuts on the skin and the immune system is not working well. Still, these are less common ways the virus spreads.

What Are the Different Pathways Involved in HPV Transmission?

HPV can spread through various pathways involving different parts of the body and interactions between individuals.

• Autoinoculation Within One Host: HPV can spread within the same person's body. This means the virus moves from one area to another on the same person's skin or mucous membranes.

• Transmission Between Individuals: HPV can pass from one person to another through direct contact or indirectly through surfaces contaminated with the virus.

Interindividual transmission occurs in various ways:

1. Perinatal Transmission: HPV can be transmitted from a mother to her baby during childbirth.

2. Sexual Transmission: HPV can spread through sexual activities such as oral-genital sex, deep kissing, and indirect contact with hands.

3. Deep Kissing: Deep kissing, also known as French kissing, involves intense contact between the inner lips, tongue, and teeth. This can facilitate the transmission of HPV if one partner is infected.

4. Indirect Transmission Through Contact With Hands: HPV can be transferred indirectly through touching surfaces contaminated with the virus and then touching the mouth or genitals.

HPV transmission models are based on established patterns of multi-site transmission and natural immunity, which vary depending on the location of the mucosal site.

• Multi-site transmission pathways:

• Extragenital to extragenital.

• Extragenital to genital.

• Genital to genital.

• Genital to extragenital.

The extragenital site can refer to either the oral or anal region. Each pathway has its likelihood of transmission, which depends on factors such as the duration of sexual partnerships, the specific sexual acts performed, and the number of acts within a partnership.

How Does Autoinoculation Take Place in Individuals With HPV Infection?

• Autoinoculation between the genital and oral or anal areas may happen when there is contact with the hands or when the virus is shed in the genital region.

• Some studies show differences in how common oral HPV is in women who have HPV in their cervix. There is debate about whether women with cervical HPV also have HPV in their mouths.

• Some studies suggest a link between cervical HPV, cervical dysplasia, or cancer and a higher chance of having HPV in the mouth.

• Other studies suggest there is not much connection between HPV in the cervix and mouth.

• So, testing for HPV in both the throat and cervix might not be a good way to screen for HPV infections in the future.

• People with HPV in their genitals are at risk of getting HPV in their mouth, too, which could lead to throat cancer.

What Are the Methods of Perinatal Transmission of HPV Infection?

HPV infection can be acquired in utero via the placenta or umbilical cord blood, perinatally, or through breast milk. Vertical transmission may occur in utero through ascending infection (transplacental transmission), during vaginal delivery, at a Cesarean section, or through periconceptual transmission from the male sexual partner.

HPV can also be transmitted vertically to neonates through breastfeeding. Transmission just after delivery can occur via body-to-body contact. High carriage rates of HPV DNA detected in oral samples from newborns decrease gradually during the first three years of life. Perinatal transmission of LR-HPV (low risk) to neonates at birth has been confirmed to be associated with recurrent respiratory papillomatosis (RRP) development.

LR-HPV-related diseases such as RRP can occur in neonates and children. These can be transmitted in utero, as a transplacental or ascending infection, or during passage through an infected birth canal. Cesarean deliveries do not completely protect neonates against HPV.

HPVs, including high-risk types 16 and 18, have also been detected in tonsillar or adenoid samples from children with tonsillar or adenoid hyperplasia, chronic tonsillitis, and normal mucosa. Children may represent a reservoir of 'silent' high-risk HPV types that may be the key to HPV persistence and related carcinogenesis in adulthood.

How Does Inter-Site Transmission of HPV Infection Occur?

• Inter‐site transmission between individuals occurs through various modes, including oral sex, anal sex, or indirect transmission through contact with hands. HPV acquisition at each anatomical site can happen independently through an infected partner. Still, it is challenging to determine which sexual behaviors are responsible for HPV transmission from the genital tract to the mouth.

• Mouth‐to‐mouth transmission, through deep kissing, remains a possible source of the viruses.

• Non‐genital virus sources present under fingernails could serve as an alternate reservoir for future infection.

• Orogenital Transmission - Orogenital transmission has been proven to be the most documented route for oral HPV infection. In cases of genotype‐concordant vaginal and oral HPV infections, recent oral sexual exposure was a more significant risk factor than cumulative sexual exposure.

Conclusion:

Gardasil-9 is a vaccine available for males and females aged 9 to 26 years. It helps protect against the types of HPV that cause most cases of cancer and genital warts. People aged 27 to 45 also consider getting the HPV vaccine if they have not already. They should discuss it with their doctor to see if it is right for them. The best way to avoid sexually transmitted diseases is to avoid sexual contact altogether or be in a long-term relationship with a partner who has been tested and is not infected.