Duesberg hypothesis
The Duesberg hypothesis is the claim, associated with University of California, Berkeley professor Peter Duesberg, that various non-infectious factors such as recreational and pharmaceutical drug use are the cause of AIDS, and that HIV (human immunodeficiency virus) is a harmless passenger virus. The most prominent defenders of this hypothesis are Duesberg himself, biochemist and vitamin proponent David Rasnick, and journalist Celia Farber. The majority of the scientific community considers that Duesberg's arguments are the result of cherry-picking predominantly outdated scientific data and selectively ignoring evidence in favour of HIV's role in AIDS. There is broad scientific consensus that the Duesberg hypothesis is incorrect, and that HIV is the cause of AIDS.

# Role of legal and illegal drug use
Duesberg argues that there is a statistical correlation between trends in recreational drug use and trends in AIDS cases. He argues that the rapid increase of AIDS cases in the 1980s corresponds to a supposed epidemic of recreational drug use in the United States and Europe during the same time frame. According to the majority of experts, this claim is not supported by epidemiologic data. Duesberg's claim that recreational drug use, rather than HIV, was the cause of AIDS was specifically examined and found to be false.
Duesberg has also argued that nitrite inhalants were the cause of the epidemic of Kaposi sarcoma (KS) in gay men. However, this argument has been described as an example of the fallacy of a statistical confounding effect; it is now known that a herpesvirus, potentiated by HIV, is responsible for AIDS-associated KS.
Moreover, in addition to recreational drugs, Duesberg argues that anti-HIV drugs such as zidovudine (AZT) can cause AIDS. Duesberg's claim that antiviral medication causes AIDS is regarded as disproven by the scientific community.

## Scientific study and rejection of Duesberg's risk-AIDS hypothesis
Several studies have specifically addressed Duesberg's claim that recreational drug abuse or sexual promiscuity were responsible for the manifestations of AIDS. An early study of his claims, published in Nature in 1993, found Duesberg's drug abuse-AIDS hypothesis to have "no basis in fact".
A large prospective study followed a group of 715 homosexual men in the Vancouver, Canada area; approximately half were HIV-seropositive or became so during the follow-up period, and the remainder were HIV-seronegative. After more than 8 years of follow-up, despite similar rates of drug use, sexual contact, and other supposed risk factors in both groups, AIDS developed only in those patients who were HIV-seropositive. Similarly, CD4 counts dropped in the patients who were HIV-infected, but remained stable in the HIV-negative patients, in spite of similar rates of risk behavior. The authors concluded that "the risk-AIDS hypothesis... is clearly rejected by our data", and that "...The evidence supports the hypothesis that HIV-1 has an integral role in the CD4 depletion and progressive immune dysfunction that characterise AIDS."
Similarly, the Multicenter AIDS Cohort Study (MACS) and the Women's Interagency HIV Study (WIHS)  which between them observed more than 8,000 Americans  demonstrated that "...the presence of HIV infection is the only factor that is strongly and consistently associated with the conditions that define AIDS."

# Current AIDS definitions
Duesberg argued in 1989 that a significant number of AIDS victims had died without proof of HIV infection. However, with the use of modern culture techniques and polymerase chain reaction testing, HIV can be demonstrated in virtually all patients with AIDS. Since AIDS is now defined partially by the presence of HIV, Duesberg claims it is impossible by definition to offer evidence that AIDS doesn't require HIV. However, the first definitions of AIDS mentioned no cause; the addition of HIV positivity to the diagnostic criteria occurred only after a scientific consensus was established that HIV caused AIDS.

# AIDS in Africa
Reported AIDS cases in Africa and other parts of the developing world, where only limited attempts are made to test for HIV infection, include people who do not belong to Duesberg's preferred risk groups of drug addicts and male homosexuals, and it would be difficult to separate the collected data to exclude non-drug users and non-gays.  Presence of HIV is not required to designate a person as having HIV, in African populations.  In fact, Duesberg writes on his website that "There are no risk groups in Africa, like drug addicts and homosexuals."
According to Duesberg, the majority of African AIDS cases may be explained as malnutrition, parasitic infection, and poor sanitation, even though African AIDS cases have increased in the last two decades as HIV's prevalence has increased and as malnutrition and poor sanitation have declined in Africa.
The diseases developed by people with AIDS differ radically between African and Western populations. For example, tuberculosis is much more commonly diagnosed among AIDS patients in Africa than in Western countries, while PCP conforms to the opposite pattern. The aggressive, AIDS-associated form of Kaposi's sarcoma is fairly common among heterosexuals in some parts of Africa, but is largely restricted to gay men in the USA and Europe.

# Duesberg's offer to infect himself
Duesberg's most radical challenge to the HIV-AIDS hypothesis is his offer to infect himself with HIV.  However, he claims that it is not permissible for him to do so without the approval of the U.S. National Institutes of Health and the university that employs him. Critics regard this as a stunt, because the NIH cannot ethically give "approval" for a person to knowingly infect themselves with HIV.

# Duesberg claims that retroviruses like HIV must be harmless to survive
Peter Duesberg argues that retroviruses like HIV must be harmless to survive, because after reverse transcription of their RNA to DNA, they depend on cell division to replicate. They cannot replicate in neurons, for example, because these cells do not divide (after the age of one year). He claims that the normal mode of proliferation of retroviruses is from mother to child, thus implying the survival of the infected mother and the child for decades.
This claim may be related to the fact that about 8% of the human genome is composed of harmless retroviral sequences called retrotransposons. These sequences, such as the Alu sequence, are molecular fossils and can no longer form active virus particles. However, the presence of these fossil sequences can influence the genome around them. For example, the gene encoding for amylase production in saliva is due to a reterotransposon inserted just upstream of the body's amylase gene. The retroviral DNA's promoter sequence induces the gene to be transcribed in the mouth.
Most researchers believe that some retroviruses can cause cancer. Peter Duesberg rejects this idea.

# Scientific response to the Duesberg hypothesis
The current consensus in the scientific community is that the Duesberg hypothesis has been refuted by a large and growing mass of evidence showing that causation of AIDS by HIV is clear, that virus numbers in the blood correlate with disease progression, that a plausible mechanism for HIV's action has been proposed, and that anti-HIV medication decreases mortality and opportunistic infection in people with AIDS but.
In the December 9 1994 issue of Science (Vol. 266, No. 5191), Duesberg's methods and claims were evaluated. The authors concluded that:
- it is abundantly evident that HIV causes disease and death in hemophiliacs, a group generally lacking Duesberg's proposed risk factors.
- HIV fulfills Koch's postulates, which are one set of criteria for demonstrating a causal relationship between a microbe and a disease.
- the AIDS epidemic in Thailand cited by Duesberg as confirmation of his hypothesis is in fact evidence of the role of HIV in AIDS.
- According to researchers who conducted large-scale studies of AZT, the drug does not cause AIDS. Furthermore, researchers acknowledged that recreational drugs do cause immune abnormalities, though not the type of immunodeficiency seen in AIDS.

## Effectiveness of antiretroviral medication
The vast majority of people with AIDS have never received antiretroviral drugs, including those in developed countries prior to the licensure of AZT in 1987, and people in developing countries today where very few individuals have access to these medications.
In the mid-1980s, clinical trials enrolling patients with AIDS found that AZT given as single-drug therapy conferred a modest (and short-lived) survival advantage compared to placebo. Among HIV-infected patients who had not yet developed AIDS, placebo-controlled trials found that AZT given as single-drug therapy delayed, for a year or two, the onset of AIDS-related illnesses. Significantly, long-term follow-up of these trials did not show a prolonged benefit of AZT, but also did not indicate that the drug increased disease progression or mortality. The lack of excess AIDS cases and death in the AZT arms of these placebo-controlled trials effectively counters the argument that AZT causes AIDS.
Subsequent clinical trials found that patients receiving two-drug combinations had up to 50 percent improvements in time to progression to AIDS and in survival when compared to people receiving single-drug therapy. In more recent years, three-drug combination therapies have produced another 50 to 80 percent improvement in progression to AIDS and in survival when compared to two-drug regimens in clinical trials. Use of potent anti-HIV combination therapies has contributed to dramatic reductions in the incidence of AIDS and AIDS-related deaths in populations where these drugs are widely available, an effect which clearly would not be seen if antiretroviral drugs caused AIDS.

## AIDS in Africa
The Duesberg hypothesis argues that AIDS in Africa is the result of poor sanitation and malnutrition, not HIV.  Critics note the following facts:
- AIDS in Africa has increased during the last two decades, in tandem with the prevalence of HIV.
- Sanitation and nutrition, on the other hand, have noticeably improved since the 1980s, when the Ethiopian famine was prominent in the news, yet AIDS case rates continued to increase.
- AIDS in Africa largely kills sexually active working-age adults.
- The groups that have HIV are those dying from AIDS.  For example, in areas where surveys show 50% of people with HIV are women, that area will show that 50% of people dying from AIDS are women.  In areas where 20% of HIV+ people use recreational drugs, then 20% of the people dying from AIDS use recreational drugs.

## Opponents claim that nearly all HIV-positive people will develop AIDS
Duesberg claims as support for his idea that many drug-free HIV+ people have not yet developed AIDS; other scientists note that many other drug-free HIV+ people have developed AIDS, and that if they wait long enough, it is very likely that nearly all of the HIV+ people will develop AIDS.  Mainstream scientists also note that drug-using HIV-negative people do not seem to suffer from immune system collapse.