We’ve all heard various conspiracy theories; we may or may not find them credible, and we might chalk up opposing viewpoints to simple differences in opinion. Sometimes, however, conspiratorial narratives are woven around matters of life and death — and in such cases, the spread of such ideas can influence dangerous changes in behavior and even government policy.

AIDS denialism is based on the idea that human immunodeficiency virus (HIV) does not cause AIDS. Although the existence of HIV and its causal connection to AIDS has been thoroughly demonstrated by scientists, denialists either reject the existence of HIV altogether, or cast it as a harmless virus that doesn’t cause illness. Denialism often relies upon rhetorical strategies that are superficially convincing but intellectually hollow, including the cherry-picking of evidence, appeals to unreliable “experts,” and untestable claims. Denialists also might cite early AIDS research from the mid-1980s while ignoring more up-to-date findings and improved medical procedures. Such rhetoric creates a sense of legitimate debate in an area where there is none, and the only new evidence welcomed into the discourse is that which confirms preconceived notions.

Health decisions must be shaped by the best available evidence, and when denialism misinforms, one cannot make an informed decision.

If AIDS isn’t caused by HIV, what do denialists claim is behind the unique symptoms that characterize it? Some say that conditions such as malnutrition, or diseases that have been around for a long time, are simply being labeled as AIDS. Other denialists cast antiretroviral drugs as the cause, rather than the preventive treatment, of AIDS. Some claim that AIDS is caused by behavior, such as drug use or promiscuity — with some even saying that an accumulation of semen in the anus can cause AIDS. None of the claims is true — while AIDS can leave someone vulnerable to a wide variety of diseases, and while sharing IV equipment and engaging in unprotected sex can increase risk, there is only one cause: HIV.

Most denialists are not actual HIV experts — in fact, the only prominent denialist with a background in retroviruses (though not specifically with HIV) is Peter Duesberg, whose groundbreaking work with cancer-causing genes and retroviruses brought him fame in the 1970s. In the 1980s, however, when his views on HIV strayed ever further from scientific consensus, he became a pariah in the scientific community — a fact that fits perfectly into the “rebel” narrative that comes up so often in conspiracy theories. However, his claim that HIV does not cause AIDS, which rather is caused by drug use and other lifestyle factors, is not backed up by the huge body of evidence that scientists have amassed since the 1980s.

Such views become harmful when they are translated into advice: Denialists tend to downplay the importance of condoms and discourage HIV testing and the use of antiretrovirals. They often claim that life-saving antiretroviral drugs are toxic poisons, a Big Pharma conspiracy to rake in cash while killing innocents. Ironically, by fostering doubt in medicine and science, denialists create a market for dubious alternative treatments that allows them to rake in quite a bit of cash as well. Their customers’ suspicions toward mainstream medicine are often exploited by self-proclaimed “experts” selling disproven (and often expensive) alternative AIDS therapies, ranging from potions, herbs, and vitamins to electronic gadgets. These treatments are unevaluated for efficacy — and often ingredients are kept secret or are different from what is claimed (some contain industrial solvents, pesticides, and other harmful chemicals). And, if the promoter of these treatments insists that their product only works when antiretroviral therapies are discontinued, patients might put their health at risk.

One peddler of an alternative treatment, Matthias Rath, claims that HIV medicines are toxic and that his vitamins should be taken instead. He conducted unethical trials of his treatment in South Africa, and in 2008 was found guilty of unlawful human studies. Rath, in a pamphlet promoting his program, claimed that his vitamins were “safe because they are natural” (seemingly oblivious to many natural yet dangerous chemicals, such as ricin, strychnine, and arsenic). While a balanced diet is important for everyone, vitamin megadoses are not supported by good evidence, and Rath’s regimen was no exception.

Encouragement to forgo antiretroviral medication is most insidiously directed at pregnant people. When proper treatment is initiated early in pregnancy, there is less than a 2 percent chance of delivering a baby with HIV — compared to a 25 percent chance when HIV is not correctly managed. One tragic example lies in the case of Christine Maggiore, a prominent HIV-positive denialist who refused treatment during pregnancy and breastfed her baby. Eliza Jane was 3 years old when she succumbed to AIDS in 2005. The United States has seen a dramatic drop in pediatric HIV infections since the widespread use of antiretroviral medication and HIV screening during pregnancy. Maggiore, however, remained an outspoken denialist until her death in 2008. As an activist, she gained a fair amount of media attention, even promoting her views via a film whose publicity was aided by a Foo Fighters soundtrack.

Marginalized populations are a target for denialist ideas, as such communities might experience more widespread suspicion toward the medical establishment. In many cases, this wariness is understandable — the Tuskegee syphilis study is considered to have sown distrust toward medicine among many African Americans, and the deeply entrenched homophobia that marred mainstream psychiatry until relatively recently might render some in the LGBTQ community suspicious of medical authority. According to one large study, AIDS-related conspiracy theories are fairly widespread among African Americans, and the acceptance of denialist ideas has also been preliminarily documented among gay and bisexual men. Such beliefs might have an impact on a person’s sexual behaviors or likelihood to seek testing or treatment.

In the United States, the movement doesn’t have much political clout, but its key players have international influence. Denialism is at its deadliest when it infects public policy, as it most notoriously did in South Africa under the presidency of Thabo Mbeki. Mbeki’s policy was driven by his denialist minister of health, Manto Tshabalala-Msimang, and an AIDS advisory committee skewed by denialists like Duesberg, resulting in a ban on antiretrovirals in public hospitals. Evidence for antiretrovirals’ efficacy didn’t sway Tshabalala-Msimang, who recommended plant-based treatments such as lemon, potatoes, and garlic instead.

In South Africa, HIV rates skyrocketed from almost zero in the early 1990s to around 20 percent of the adult population in 2007 (even more grim, an estimated 1 in 3 women in the 25-to-29 age group is estimated to be HIV positive). By the time Mbeki resigned in 2008, 2.6 million South Africans had died of AIDS; Harvard researchers attributed 365,000 deaths to Mbeki’s policies. (The new president immediately fired Tshabalala-Msimang; South African AIDS policy is being modernized.)

Conspiracy theories that arise from suspicions toward science and medicine undermine prevention, screening, and treatment of disease. Whether this suspicion is aimed toward HIV medications, vaccines, cancer treatments, obstetrics, or other evidence-based medicine, the result is the same: Patients are disempowered from making decisions based on the most complete and reliable information. When denialism misinforms, one cannot make an informed decision. Freedom of choice and bodily autonomy aren’t worth as much when we fall prey to junk science and pseudoscience, myth and misinformation.

More information about AIDS denialism can be found at Science magazine’s website. Avert.org provides tips for spotting bogus HIV treatments. HIV testing can be obtained at any Planned Parenthood health center.