jueves, 3 de mayo de 2012
HPV transmission—still feeling the way
Lancet. 1999 Dec 18-25;354(9196):2097-8.
Some sexually transmitted infections such as gonorrhoea, syphilis, molluscum contagiosum, hepatitis B, herpes simplex virus, pubic lice, and scabies can be transmitted via non-sexual routes (fomites, fingers, nonsexual skin-to-skin contact, and perhaps flies).1
However, sexual intercourse (including genital-togenital, orogenital, and anogenital contact) remains by far the most important route of transmission.
Most cases of genital human papillomavirus (HPV) infection are transmitted sexually.2 However, understanding of the exact modes of and risk factors for transmission of genital HPV has been hampered by the high rate of subclinical infections and the lack of a routine test that is sensitive and specific. Non-sexual transmission of genital HPV has been thought to occur among adults and among children. In the first half of this century, genital warts were believed to be transmitted by hand-genital rather than sexual contact.3 More recently, anogenital warts in children have been reported to occur as a result of hand warts in the child or relatives, mostly via non-sexual contact.4,5 This conclusion is supported by the observation that many anogenital warts in children are caused by HPV types 1–4, the types commonly found on the hands.6 Now, C Sonnex and colleagues7 have shown that HPV DNA of the genital types can be detected on the fingers of some men and women with genital HPV infections, evidence which supports the possibility that these infections could be transmitted via fingers from one adult to another.
Sexual activity often involves contact between hands and genitals. However, for transmission to occur several steps are necessary. First, intact, live virus needs to be transferred from the genitals to the fingers. The detection of HPV DNA does not necessarily imply the presence of intact, infectious virus.8 Second, most HPV types seem to be site specific.2 Consequently genital HPV types probably do not cause finger warts, rather contaminated fingers just carrying a virus may transfer HPV to the genitals. This seems to differ from the situation of “active” transfer of skin warts from hands to genitals as described above in children, and as occasionally occurs in adults. Third, a sufficient quantity of live virus would need to be transferred from fingers to the partner’s genital tract. Hand-washing probably reduces the quantity of infectious virus. The “ infectious dose” of HPVs including genital HPV types is unknown.
Finally, some breach of the genital skin or mucosa may be necessary to allow entry of the virus, since infection takes place in the basal-cell layer of the genital squamous epithelium.9
Although each of these steps is possible, the whole sequence of events probably rarely occurs. In addition, in most circumstances, contact between hands and genitals is usually accompanied by genital-to-genital contact by which transmission is far more likely to occur because of the presence of a large amount of infectious virus and the microtrauma that commonly occurs with sexual intercourse.9
Carriage of HPV DNA on the hands of individuals with genital warts probably does not have any major
public or personal health implications. And apart from general advice about personal hygiene and handwashing, there does not seem to be any specific advice to offer. A recommendation to wear rubber gloves for all sexual contact is unlikely to enjoy much support from the general public. On the other hand, a recent casecontrol study has shown that condoms may offer substantial protection against genital warts.10 In that study, in both sexes, failure to use condoms was independently associated with an increased risk of genital warts in men (odds ratio 3·0 [95% CI 2·2–4·3]) and in women (1·7 [1·0–2·9]), whereas consistent condom use was associated with a decreased risk of warts in men and women (0·7 [0·3–0·9] and 0·7 [0·4–1·0], r espectively).10
Transmission of genital HPV by fingers may occur occasionally. However, most infections almost certainly occur because of genital-to-genital contact. At present, the only intervention that is proven to reduce the risk of genital warts is consistent condom use. Consequently, current efforts should remain directed at convincing sexually active individuals to cover their genitals, rather than their hands, with rubber.
*Adrian Mindel, Robin Tideman
Academic Unit of Sexual Health Medicine, S ydney Hospital, S ydney,
New South Wales 2001, A ustralia
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