Should There Be Prison Time for Unknowingly Transmitting HIV?

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

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New fossils suggest human ancestors evolved in Europe, not Africa

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  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
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Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.