HPV


Cancer of the uterine cervix is a sexually transmitted disease; it is the second most common cancer of women in the world and it is spread sexually. Who would have guessed? The clues were there all along, of course: it was more common in sex workers, and women who had become sexually active at an early age; it was rare in nuns… But it took a while to connect the dots -and for technology to catch up with suspicions: viruses couldn’t even be visualized until the invention of the electron microscope, although their existence was suspected much earlier using filters with holes too small for bacteria to pass through. And then their DNA had to be identified in cervical cancer cells… and classified. It was a long journey all right.

But sexual transmission? The jump from abnormal Pap smear to the bedroom was -and is- a hard sell.  The fact that more than 80% of sexually active humans have been exposed to the virus was hard enough, but add to that the knowledge that the vast majority of teenage infections will clear on their own because of the vigorous immune response at that age, and you have a recipe for confusion. Or complacency.

Cancer of the cervix is rare before the age of 25 -the virus has a long prodromal developmental period- so after telling women how important Pap smears were in preventing, or at least detecting, this infectious cancer, raising the age of the initial Pap smear from the time of first sexual activity to age 21 in North America, did little to foster understanding. And then playing with the frequency and mode of surveillance for the rest of the age groups… Well, it was almost a breach of trust; changing the rules after years of teaching was just not on.

I mention this only to put the contemporary problems of counselling young women into some perspective. Especially now that vaccination against some of the more common and troublesome varieties of Human Papilloma Virus is possible. Vaccination has always had its opponents, and HPV is no different. But for my practice, there seem to be two major questions that arise: the need for continuing screening after vaccination, and the need for vaccination if a woman has already had a pre-cancerous condition treated.

These are confusing, if not vexing questions. There are at least 15 types of HPV that cause cancer but only two major varieties that account for the vast majority of cases in the community: types 16 and 18 (they’re numbered, rather than given cutesy names). These are the strains that are incorporated into the current vaccines. So if a woman has already had dysplasia -the pre-cancerous condition caused by the virus- it will have been caused by only one of those types and she is still vulnerable to the other. And therefore she still needs to be vaccinated. I get asked this every day, I think. Fortunately the schools in my province have incorporated the HPV vaccination into the early grades at school -hopefully before sexual exposure- so the question may well be an anachronism in the foreseeable future.

But the need for continuing screening in a vaccinated population is more difficult to understand in an era brought up on the concept of herd immunity: the idea that the more people who are vaccinated, the less prevalent the virus, and hence the less chance of being exposed to it. What tends to get forgotten, however, is that there is never a completely protected group: we are a heterogeneous society with new, unprotected people entering it from outside; immunity may wane; less common strains or perhaps novel viruses might gain prevalence and not be incorporated into the contemporary vaccine products. No, there are many reasons not to let down the guard of vigilant surveillance.

But a problem still persists: HPV doesn’t behave at all like a sexually transmitted infection in the minds of most people. We have come to expect cause and effect to be temporally accountable: the unprotected sexual encounter last week results in identifiable symptoms this week. Blame is assignable; lessons are learned. But with HPV, cause and effect are often separated by uncharted and imponderable years of time. There are seldom symptoms, seldom acquired wisdom. No one -or everyone- seems culpable: a difficult take-home message indeed. As I have already suggested, the voyage from Pap to Prevention is a stormy one.

But maybe this is just a generational thing: what we find difficult to assimilate today, will be greeted with a knowledgeable shrug tomorrow. We are creatures of more than structural evolution; more than linear accrual. As Shakespeare says: We know what we are, but know not what we may be. Or even better: Lord, what fools these mortals be!

One thought on “HPV

  1. gozzter says:

    Hi Cameron. What was your question?

    Like

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