Transmission of HPV
Visible genital warts and subclinical HPV infection nearly always arise from direct skin to skin contact:
- Sexual contact. This is the most common way amongst adults.
- Oral sex. HPV appears to prefer the genital area to the mouth however.
- Vertical (mother to baby) transmission.
- Auto (self) inoculation from one site to another.
- Fomites (i.e. from objects like bath towels). It remains very controversial whether warts can spread this way.
Neonatal infection may arise by passing through an infected birth canal. This can lead to rare complications, such as laryngeal papillomatosis i.e. warts in the throat. Because this complication is unlikely, a caesarean section is rarely indicated simply because a pregnant woman has genital warts.
In small children, genital warts raise the possibility of sexual abuse but in many cases it is due to vertical transmission (see above).
Transmission is common as genital warts often go unnoticed. Subclinical infections can also be infectious.
Often, warts will appear three to six months after infection but latency periods of many months or even years have been reported. Developing genital warts during a long-term relationship does not necessarily imply infidelity.
Visible warts are probably more infectious than subclinical HPV infection. Treating warts seems to decrease the chance of passing on the infection. We cannot tell whether the immune system completely clears the virus from the body, or whether the virus remains hidden but undetectable, capable of re-emerging years later if the immune system weakens. As a result, it is unclear how long someone remains infectious.
The risk of HPV transmission is extremely low if no warts recur a year after successful treatment.
