Syphilis cannot be eradicated

Syphilis is back. As the most widespread venereal disease in the 1930's it was curtailed after huge efforts, both in developed and developing countries. And ten years ago a push was made to finally eradicate it. But syphilis is quietly making a comeback, hidden in the shadows of AIDS. And because the transmission of this disease is primarily driven by risky sexual behavior, it can be a leading indicator of other sexually transmitted diseases on the rise.

David Aadland, David Finnoff and Kevin Huang use a model of human behavioral response to study this resurgence and come to the conclusion that there is a fundamental cycle that cannot be broken. The point is that the transmission model that epidemiologists use has constant parameters tracing back to biological features of the disease, but these parameters can change through human intervention, and they do. Call this a Lucas Critique of epidemiology. The key here is that when prevalence is low, individuals in a riskier fashion and in particular have more sexual partners. No reasonable policy can overcome this.