"The department says genital herpes can double a person's risk for contracting HIV. Herpes can cause painful sores, but most people have no recognizable symptoms. Among New Yorkers, the herpes rate is higher among women, black people and gay men."So, what to make of this. First, as with the previous post on chlamydia, I think one has to keep in mind which STD is being referenced here. Herpes and chlamydia, we're learning, are much more common than we previously thought, but do not mistake that to mean that all STDs are more common, or that this increase in reporting represents an increase in actual, underlying prevalence. The problem with both herpes and chlamydia is that both are asymptomatic What this means is that infected individuals do not get treated when they become innoculated, which therefore means the window of time a person remains both infected and connected actively to the sexual network is longer. Possibly much longer. Gonorrhea and syphilis, on the other hand, are relatively symptomatic infections, and it's probably at least partly due to that accidental feature of the infections that both have been falling over the last few decades (except among gay males, where syphilis has begun rising again). An STD that remains hidden will not be treated, and thus from the perspective of the infection's genetic fitness, seems to increase the probability of moving throughout the network from host to uninfected host. Infections that have symptoms, on the other hand, will get treated, thus limiting exposure to uninfected people, and therefore decreasing the chances of spread throughout the network.
But why higher among women, blacks and gay males? For the first explanation, it's got to do probably with the simple fact that the per-act probability of infection for male-to-female is 0.002 (ie, .2% of the time, an infected male will infect an uninfected female during unprotected vaginal intercourse), whereas it is 0.0004 for female-to-male (ie, .04% of the time). In other words, a female is five times more likely to get infected when having sex with an infected male than an uninfected male is when having sex with an infected female. You can therefore imagine that small differences in these infectivity rates can lead to sexual disparities in a longrun equilibrium.
But what about gay males? This is easy. Gay males engage are more likely to engage in anal receptive intercourse, which has both a higher condom failure rate than vaginal intercourse and independently has a higher transmission rate for nearly all STDs. But then what about Blacks? We don't know exactly why Blacks have higher rates of STDs, but one possibility is that it's due to the higher rates of "concurrency" within Black sexual networks. Adimora and Schoenbach are two epidemiologists at Chapel Hill who have written extensively on this. They argue that concurrency rates (that is, the occurrence of more simultaneous or overlapping sexual partnerships in a sexual network) are higher in Black networks due in part to higher rates of incarceration in the black community. Relatively higher rates of male incarceration leaves an imbalanced sex ratio in the mating markets, causing men with "tastes for promiscuity" to have opportunities for multiple girlfriends. Cunningham and Cornwell find some evidence consistent with this hypothesis in the working paper "Sex Ratios and Risky Sexual Behavior."
It's also independently possible that men are getting herpes in prison, and thus spreading it to female partners upon release. Some studies show this could be happening with AIDS, so it's possible assuming there is some herpes in prisons that it's happening with it too.
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