In 2008, 41,269 people in the U.S. were diagnosed with HIV, an increase of 8% from only three years earlier. Known infections make up only 75% of total infections, leaving 25% of HIV infected people unaware that they have the disease. The transmission of HIV by people who are unaware is estimated to be at least three and half times the rate of the transmission of HIV by people who are aware of their infection status.* The penalty for exposing another individual to HIV varies from state to state, but there is not one state that considers unknowingly infecting another individual with HIV a criminal offense. With the prevalence of this disease increasing, is it time for a new set of laws that send an individual to prison for transmitting the disease—even when they don’t know that they have it?
The probability of being infected with HIV, even if you are having sex with an infected person, is quite low. For example, the probability of infection from the riskiest behavior, anal receptive sex, is less than 1% (on a per-act basis). The probability of infection for a woman having vaginal sex, 0.09%, is so small that it is hard to argue that you are likely to be infected. These low rates of transmission are over the life of the disease, however, and don’t accurately reflect the transmission rates in the early stages of infection when most people are likely to be unaware. The probability of transmission is considerably higher before, and for about 6 months after, the antibodies are detectable in the blood. This explains why people who are unaware of their infection status are significantly more likely to transmit the disease.
It may not seem very fair to send someone to prison for transmitting a disease that they don’t know they have, but according to a paper written by two economists at Emory University, that is the socially optimal policy. A policy is socially optimal if it reduces the overall infection rate—fairness has nothing to do with it. They suggest that any individual who transmits the HIV to another person, knowingly or unknowingly, should receive between one and two years of prison time. They also suggest that anyone who exposes another individual to the disease without transmission should have no penalty. Both of these results seem counter-intuitive, but in a game theoretic sense, where individuals are making choices based on expected outcomes, these policies should both lead to lower infection rates.
Let’s deal with the exposure without transmission issue first: Should someone who exposes another individual to HIV be penalized even if they do not infect the other person? Most states impose penalties for knowingly exposing another individual to HIV, with penalties ranging from minor fines to serious jail time (and exceptions made in some cases for disclosure and/or condom use). Only one state imposes a penalty just for transmission and not exposure (Utah, which has a maximum fine of $2,500 for transmission).
Imagine that you have HIV and you are about to have sex with someone who doesn’t know your HIV status. You have no intention of informing them that you are infected, but can choose to use a condom to protect them from transmission. If the penalty for transmission is the same as exposure then what is the incentive, from a legal perspective, of making the choice to reduce the partner’s risk? In the current set of laws there is none and, if you don’t care about infecting the other person, you might very well forgo the condom.
This may seem a bit crazy, since you might reasonably assume that if you are having sex with someone you care about their well-being. But imagine that the infected person is a sex worker and that they can charge a premium for sex without a condom. If they are already infected with HIV then they have little to lose from condomless sex. If the legal penalty is the same for exposure as it is for transmission, then why not have condomless sex with a person who is willing to pay a little more for the privilege?
The law that treats exposure the same way as transmission increases risky sex, and changing the law to penalize only transmission should, in a perfect game theory world, increase condom use.
So should people who unknowingly transmit the infection be penalized along with everyone else? Unfair as it may seem, imposing penalties for those who are unaware of their status should increase both the rate of HIV testing and of condom use. According to the Center for Disease Control and Prevention (CDC) an estimated 1.1 million people living in the US are infected with HIV. If 25% of those have an unknown infection, this means there are about 275,000 people who could be unknowingly spreading the disease. Add to this the medical fact that these people have the highest probability of transmitting the disease, it isn’t that difficult to accept the notion that prison time for unknowing transmission is the socially optimal policy.
This is the decision to be made: Is reducing the transmission of the HIV worth the price of sending individuals, who already have a chronic medical condition, to prison for two years when they were unaware that they were likely to infect another person? That isn’t a question for an economist. My guess, though, is that for most societies that is too high a price to pay.
* Marks, Gary, Nicole Crepaz and Robert S. Janssen (2006). “Estimating sexual transmission of HIV from persons aware and unaware that they are infected with the virus in the USA.” AIDS Vol. 20(10): pp. 1447-1450. doi: 10.1097/01
** Francis, Andrew M. and Hugo M. Mialon (2006). “The Optimal Penalty for Sexually Transmitting HIV.” American Law and Economics Review Vol. 10(2). doi:10.1093/aler/ahn013