Here we summarize the fake “questions” Leung raises in the film, and provide real, evidence-based answers.
“House of Numbers” asks if there is really a scientific consensus about HIV/AIDS. The real answer is: YES.  There is an overwhelming scientific consensus, based on incontrovertible evidence, that HIV exists and is the cause of AIDS. The scientific evidence has shown conclusively that HIV exists, is transmitted by the blood and sexual fluids of infected people, and gradually destroys the human immune system, resulting in AIDS, a syndrome manifesting in various diseases that healthy people fight off but that cause illness and ultimately death in people with advanced HIV disease.  Before the advent of antiviral medications, people with advanced HIV disease had multiple, devastating infections and symptoms that would not seriously harm a person with a healthy immune system.  Since 1981, over 25 million people worldwide have died from HIV/AIDS.

The makers of “House of Numbers” deceived legitimate HIV researchers, infectious disease doctors, and AIDS activists and philanthropists to get interviews with them, and they edited the footage to make it seem that there is disagreement that HIV exists and is the necessary cause of AIDS. These facts have been established in laboratories, clinically, and by epidemiology, and published in tens of thousands of peer-reviewed publications. We have much still to learn about HIV and AIDS, and some scientists don’t like each other, but no legitimate, qualified scientist or doctor questions the existence or consequences of the virus.

“House of Numbers” questions the reliability of the HIV test. Does the HIV antibody test actually tell us anything at all?
The real answer is: YES. HIV tests are extremely reliable, sensitive and specific. What is usually referred to as the “HIV test” is just one step in HIV screening and diagnosis. The ELISA or EIA test screens for the presence of HIV antibodies in blood or oral fluids.  In any diagnostic tests, there is a balance between sensitivity (recognizing everyone who is a true positive, who has the virus or whatever is tested for) and specificity  (recognizing everyone who is a true negative, who doesn’t have the virus or whatever is tested for).  Greater sensitivity always means more false positives, because very sensitive test will react to some things that are not the virus as if it were.  Although rare, HIV false positives can happen: they are caused by the ELISA test reacting to antibodies produced in pregnancy or from some autoimmune diseases.  (It is not true, as denialists claim, that 70 different conditions can cause false positives. And false positives are a feature of all screening tests, not just those for HIV.  For example, some men will test positive for pregnancy. It doesn’t mean they are pregnant, or that pregnancy tests are totally useless, or that pregnancy doesn’t exist: it only means that the test is calibrated to capture all pregnancies when used correctly because a false negative is a bigger problem than a false positive.)

The ELISA test for HIV is very sensitive, because it is used to screen the blood supply and any false negatives could result in the HIV infection of hundreds of people.   A positive ELISA test is 99.5% sensitive after the “window period” following infection, before HIV antibodies have developed.  Because there is a small risk of a false positive, every HIV test is then confirmed with a Western Blot test.  The two-test protocol is over 99.9% accurate, and clinical monitoring of a patient’s viral load and immune system by a physician further confirms the diagnosis.   Misdiagnoses of HIV infection resulting in inappropriate treatment with antiretroviral drugs are extremely rare and are considered malpractice. (In 2007, an HIV-negative Massachusetts woman, Audrey Serrano, sued and won $2.5 million in damages against the doctor who treated her for AIDS without confirming that she was HIV infected.  The HIV testing technology is so good that there is simply no excuse for the mistake that her doctor made.)

“House of Numbers” questions the practice of asking about risk factors in testing and diagnosis. Don’t doctors just want to know if you are gay or a drug user, and isn’t the diagnosis really bogus?
The real answer is: NO.  Questions about risk factors are part of good screening, diagnosis and care. One step in many HIV testing protocols is an interview to assess the individual’s risk of infection.  This has value as for prevention education; in addition, knowledge about risk helps frame the accuracy of a screening test.  For straightforward statistical reasons, the likelihood of a false positive is higher where there are no risk factors and low prevalence than where risk factors and prevalence are high.  But every positive ELISA test is still confirmed by a Western Blot or other test.   The HIV tester in the movie who says that an AIDS diagnosis would be dependent on risks being acknowledged in an interview was simply wrong.  It seems likely that she was asked misleading questions by the interviewers.

“House of Numbers” questions why some people who are exposed to HIV are not infected. Maybe HIV isn’t communicable?  Maybe it doesn’t exist?
The real answers are NO and NO. There is no virus for which exposure always leads to infection. It should be obvious that not everyone exposed to a pathogen gets sick.  Everyone knows that when someone in an office has a cold, some co-workers will catch it, and others won’t: how many do get sick depends in part on what steps people take to reduce the possibility of transmission.  In the film, denialist Liam Scheff says that scientists say that HIV is so infectious it “leaps of penises into vaginas.” That’s a lie—people knowledgeable about HIV are clear that HIV is a hard virus to get—but the consequences of infection are serious, so prevention is crucial.  The likelihood that a virus, including HIV, will be transmitted depends on many factors, including the nature of the contact, the innate transmissibility of the particular virus, the nature of the exposure or contact, how long the virus survives outside the body, and the viral load of the person who has it (people recently infected have very high levels of virus, while people on antiretroviral HIV medications have low, sometimes undetectable levels).  This may be complicated, but it isn’t unusual at all. (And be aware that many HIV denialists reject the existence not only of HIV but of ALL viruses, and even of the role of germs in disease!)

“House of Numbers” questions how one disease varies so much in different people.  Could it be that there’s no such disease as AIDS?
The real answer is: No. HIV infection will, over time, destroy the immune system in almost all infected people.  The immune system is then unable to fight off opportunistic infections that are present in the environment, and they will get sick and die.  Different strains of the virus and different regionally endemic diseases that affect immune-compromised people account for geographic variation in HIV disease patterns.  Once a person is infected, the rate of disease progression is affected by many factors—the strain of the virus and the person’s age, overall health, environment, nutrition.

Causality does not require uniformity to be demonstrated. While there is a period averaging ten years when an HIV-positive person is clinically asymptomatic (that is, has no major symptoms), there is great variation between people’s HIV disease progression, even within the same region or even household.  For example, Christine Maggiore, an HIV-infected denialist, said she first tested positive in 1992: she survived without HIV treatment for fifteen years until her death from AIDS last December. Her daughter, to whom she transmitted the virus perinatally, survived only 3 ½ years without treatment: she died, tragically and unnecessarily, of AIDS in 2005.

“House of Numbers” asks if a disease that is diagnosed differently on different continents is really only one disease.
The real answer is: YES.  It is all HIV disease, and how the doctors and public health officials in different countries decide to mark the point at which it becomes full-blown  “AIDS” doesn’t alter the reality of the virus and its effects.  The virus doesn’t care what you call it, and the progression of the untreated disease is not driven by, but only expressed in, diagnostic language.  Differences in diagnostic criteria by region reflect lack of access to HIV testing technologies and different clinical approaches: specifically, most African countries’ health systems cannot afford HIV testing. That doesn’t mean that HIV doesn’t exist or that poverty causes AIDS. Where HIV tests are not available, an AIDS diagnosis obviously cannot include HIV status as an element of an AIDS diagnosis, so the diagnosis is based on the presence of opportunistic infections that would only afflict a person with a compromised immune system.

“House of Numbers” asks if the profits that pharmaceutical companies make from HIV drugs might in fact be the reason for the invention of HIV/AIDS.
The real answer is: NO. The fact that the pharmaceutical industry does make money from HIV drugs does not mean that there is no such thing as HIV or AIDS.  From the earliest days of the epidemic, AIDS activists have demanded the pharmaceutical industry and the government do smarter, more ethical, and expanded research. Activists have fought for the rapid development of better, more effective, more tolerable, and more affordable treatments for HIV, and the current generation of antiretroviral drugs for HIV are effective and easily tolerated by most people living with the virus.  But that can lead to complacency and even the HIV denialism showcased by “House of Numbers. ”  We must continue to fight to make HIV treatment accessible and affordable to everyone who needs it, including through the production of generics and international trade strategies like compulsory licensing that cut into the drug companies’ profits. We need to fight for prevention strategies that are science-based and really work, like needle-exchange and condoms, and more fundamentally address the structural injustices that render some populations much more vulnerable to HIV, as well as to other diseases.  And we must press for the development of vaccines, other prevention technologies like microbicides and post-exposure prophylaxis, and ultimately for a cure.