HIV/AIDS: an overview of a world-changing pandemic

last updated: Oct 03, 2019

14 min read

It's hard to believe, but AIDS, and HIV, the virus that causes it, have only been recognized in the United States since the early 1980s. In the few short decades since they were discovered, HIV/AIDS has gone from being universally deadly to being a highly treatable chronic disease with an almost average life expectancy in those who are adequately treated. Furthermore, modern HIV regimens are very well tolerated. This means that most people with HIV can lead normal lives so long as they take their medicine.

Despite the success of modern medicine in addressing the HIV/AIDS epidemic, there is still a lot of misinformation out there. Don't worry; we have you covered. Read on for the lowdown on HIV/AIDS from screening and diagnosis to treatment and prevention.


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HIV is still a significant public health concern

While modern medical advances have made HIV a very treatable disease, it is still a significant public health concern. Without treatment, HIV is still deadly. The Centers for Disease Control and Prevention (CDC) estimates that about 1.1 million people over the age of 13 in the US are living with HIV, and about 14% of them are undiagnosed (CDC, 2019). This is important because undiagnosed people constitute a significant source of transmission of HIV. In 2017, there were almost 39,000 new cases of HIV diagnosed in the US. High-risk groups include men who have sex with men (MSM) and IV drug users (IVDUs), with about two-thirds of new cases in MSM. In 2016, approximately 16,000 people with HIV died, but many of these people died from causes other than HIV. This reflects the advances in diagnosis and treatment, considering that over 1 million people are living with the virus.

What's the difference between HIV and AIDS?

One of the things that sometimes confuses people is the difference between HIV and AIDS. HIV is the human retrovirus that causes AIDS if it is not treated properly. Retroviruses are viruses containing RNA as their genetic material. The virus uses an enzyme called reverse transcriptase to make DNA from RNA. The viral DNA is then inserted into the infected cell's DNA to make more viral particles, which go on to infect other cells.

AIDS is a disease of the immune system caused by the HIV virus. The HIV virus infects specific cells of the immune system (CD4+ T cells, macrophages, and dendritic cells) and, over time, destroys the populations of these cells. CD4 cells play an important role in directing the immune system. AIDS is the most advanced stage of HIV infection. It is defined as having a CD4 count of fewer than 200 cells/mm³ or having HIV and an AIDS-defining illness, such as Pneumocystis jiroveci pneumonia or Kaposi's sarcoma. Today, most people with HIV will never be diagnosed with AIDS, provided that they receive proper treatment with modern HIV regimens.

History and discovery of HIV

The history of HIV and the medical advances addressing the epidemic is a fascinating tale of a triumph of modern medicine. Scientists believe that HIV came from a virus in West Africa that infected chimpanzees called simian immunodeficiency virus (SIV). Humans contracted the virus when they came into contact with infected blood through hunting. At some point, the virus mutated into the human form, HIV, but it was not recognized until the 1980s (, 2019).

In 1981, doctors in the US began to see a new rash of young people, primarily MSM, with severe immunodeficiency (poor immune systems) and opportunistic infections (infections with organisms that usually don't cause disease). Most of these people were diagnosed with Pneumocystis carinii pneumonia (PCP), now called Pneumocystis jiroveci pneumonia (PJP), a rare lung infection, and Kaposi's sarcoma (KS), an aggressive cancer of the blood vessels. These and other opportunistic infections would later be recognized as AIDS-defining illnesses. In that year alone, there were 337 reported cases of severe immune deficiency and opportunistic infections, and over a third of them, 130, were dead by the end of the year. By 1989, the number of reported cases of AIDS in the US had reached 100,000. Panic gripped the public, as in those early years, AIDS was a terminal illness, killing its victims an average of 15 months after diagnosis. Even babies were dying of the disease.

The term AIDS, or acquired immune deficiency syndrome (or acquired immunodeficiency syndrome), was first coined in 1982, although the human immunodeficiency virus (HIV), the virus that causes AIDS, was not discovered until 1983, and not called HIV until 1986. In 1987, just six years after doctors saw the first cases of PCP and KS, zidovudine (AZT) was the first medication that was FDA-approved to treat AIDS. AZT is part of a family of drugs called nucleoside reverse transcriptase inhibitors (NRTIs). These drugs work by preventing reverse transcriptase from making viral DNA out of its RNA, an important step in the HIV life cycle.

Although AZT showed early activity against the HIV virus, the virus rebounded shortly after starting the drug, only this time the virus had changed; it had mutated to be resistant to the effects of AZT. Drug development continued slowly, with three new NRTI drug approvals in the early 1990s.

In 1995, the first protease inhibitor (PI), saquinavir (brand name Invirase), was approved and marked the beginning of the era of HAART, or highly active antiretroviral therapy. PIs block another important step in the HIV life cycle. As it became apparent that no single drug was the answer, drug combinations began to be recommended for HIV treatment, and, within two years, AIDS-related deaths had decreased by almost 50%. The 1990s and early 2000s saw an HIV drug explosion, with 16 new drugs from four different families and five fixed-dose combinations (FDCs). The medical community continued to study various combinations of medications to produce the best response with the least side effects, and this quest continues today. The first integrase strand transfer inhibitor (INSTI), raltegravir (brand name Isentress), was approved in 2007. Since then, three other INSTIs have been approved, and these drugs now form the backbone of modern HIV multi-drug regimens due to their high effectiveness and favorable side effect profile. INSTIs work by preventing viral DNA from being inserted into the infected cell's DNA, which is required for the virus to multiply.

Evolution of understanding & early misconceptions

One of the early misconceptions about HIV/AIDS was regarding the populations at risk for the disease. This is reflected in the term Gay-Related Immune Deficiency (GRID), which was used in the press and by some researchers in the early 1980s. Since most of the people being diagnosed were MSM, some people thought that it was a "gay disease." While MSM continue to represent two-thirds of new infections in the US and three-quarters of new infections in men, we know that there are other high-risk groups. Along with other forms of transmission, heterosexual contact accounts for approximately 25% of new cases of HIV in the US. 

Another early misconception about HIV was that it could be transmitted through casual contact with an infected person. The CDC ruled out the possibility of transmission through air, water, environmental surfaces, and casual contact in 1983. In 1984, a report in the New York Times suggested that HIV could be transmitted through saliva. This was proven false two years later.

Since people were initially being diagnosed at very advanced stages of HIV in the 1980s, some people thought they could tell if potential partners were sick just by looking at them to see if they looked healthy. What was not appreciated at the time is that HIV can be asymptomatic for ten years or more after the initial infection. During this time, HIV is highly transmissible to sex partners and through needle sharing.

Some myths about HIV persist today. For example, some people think condoms are no longer necessary if they and their partners are both HIV positive. It's important to understand that it is possible to transfer different strains of HIV from one person infected with HIV to another. This becomes especially problematic if one partner is infected with a mutated, drug-resistant virus. 

Another myth that persists is that an HIV diagnosis is a death sentence. This was true until the advent of modern HIV drug regimens. However, with proper treatment, HIV no longer carries this sort of prognosis, and people with HIV can live a long and healthy life.

How is HIV transmitted?

HIV can be transmitted through certain body fluids, including blood, semen (including pre-cum), vaginal fluids, and breast milk. These fluids must come in contact with a mucous membrane or damaged tissue or be directly injected into your bloodstream. Mucous membranes are the shiny, pink skin lining the mouth, throat, nose, vagina, and male urethra. HIV can also be transmitted from mother to child during childbirth. 

It's important to remember that these are the only ways that HIV is transmitted.

HIV is not transmitted through:

  • Hugging 

  • Social (closed mouth) kissing 

  • Breathing the air of someone who is infected

  • Tears

  • Pets

  • Insects

  • Touching inanimate objects

The risk of acquiring HIV from blood products or a blood transfusion is virtually zero, with an estimated risk of less than one in a million since the widespread screening of donated blood products. 

The vast majority of cases of HIV transmission are caused by anal or vaginal sex with an infected person or sharing needles or other injection paraphernalia with someone who is HIV positive.

Although rare, it is possible to transmit HIV through the following activities:

  • Deep (open mouth) kissing if both partners have bleeding gums

  • Oral sex

  • Being bitten by someone with HIV 

  • Contacted between blood or other body fluids (semen, vaginal fluid) that is infected with HIV and an open wound

  • Blood transfusions (the risk is estimated to be less than 1 in a million)

What are the risk factors for HIV infection?

Knowing the risk factors for HIV allows you to minimize the risk of contracting the virus. The most important risk factors for HIV are:

  • Having unprotected anal or vaginal sex, especially with multiple sexual partners 

  • Sharing needles or other paraphernalia for injecting drugs

When it comes to sex, some behaviors carry more risk than others. Here is a list of various types of sex in order of highest to lowest risk for HIV transmission:

  • Receptive anal intercourse ("bottoming")

  • Insertive anal intercourse ("topping")

  • Receptive vaginal intercourse

  • Insertive vaginal intercourse

  • Receptive or insertive oral intercourse (low risk)

There are various ways to lower the risk of acquiring HIV. Being in a monogamous relationship with a partner who is HIV negative is the best way to prevent HIV. Condoms are also an important tool for HIV prevention. When using condoms to prevent HIV, make sure to use latex or polyurethane condoms. Do not use lambskin condoms as these do not reliably protect against HIV. If you inject drugs, do not share needles or other materials. Needle exchange programs may be an effective tool for preventing HIV transmission at the population level. For certain people, taking medication before they have HIV is an effective preventive strategy.

Pre-exposure prophylaxis (PrEP)

It may sound odd, but research shows that taking a medication called Truvada (emtricitabine/tenofovir disoproxil fumarate) can reduce the risk of HIV transmission by about 99% in people at high risk due to sexual exposures and 74% in those at high risk due to injection drug use when taken daily. Truvada is a single pill containing two medications that are usually used as part of a three-drug regimen when used to treat someone already infected with HIV. The following groups are eligible for PrEP according to the CDC (CDC, 2018):

  • MSM (including bisexual men) who are not in monogamous relationships with an HIV negative partner and have had unprotected anal sex (top or bottom) or a bacterial sexually transmitted infection (STI) such as syphilis, gonorrhea, or chlamydia in the past six months.

  • Heterosexually active men and women (MSW or WSM) who are not in monogamous relationships with an HIV negative partner and does not consistently use condoms during sex with one or more partners of unknown HIV status who are known to be at substantial risk of HIV infection (MSM or IVDU)

  • People who inject drugs and have shared needles or other drug preparation materials in the past six months

A negative HIV test is required before starting PrEP because taking Truvada in someone with HIV is not considered a full HIV regimen and can induce viral resistance. HIV tests are required every three months to continue PrEP, and testing for other STIs is also recommended. In addition, kidney function should be tested once before starting PrEP and every six months thereafter.

On October 3, 2019, the US Food and Drug Administration (FDA) approved Descovy for PrEP, excluding those at high-risk due to receptive vaginal sex (FDA-c, 2019). Descovy has the same two active ingredients as Truvada, but the tenofovir is in a different form (tenofovir alafenamide). This form of tenofovir is considered a safer form of the drug. It remains to be seen what role Descovy will play in PrEP in the future. Several methods of long-acting PrEP are also being studied but are not yet available (, 2019).

Post-exposure prophylaxis (PEP)

As the name suggests, post-exposure prophylaxis (PEP) is indicated for people who may have been recently exposed to HIV. To be effective, PEP needs to be taken within 72 hours after a possible exposure to HIV, whether it was a needlestick injury or unprotected sex with an individual of unknown HIV status. PEP is then taken for a further four weeks. You can think of the difference between PrEP and PEP as similar to the difference between the birth control pill and the morning after pill. In both instances, the latter is not intended for regular use but emergencies. While PEP is not 100% effective, it can decrease the chances of acquiring HIV if started early enough.

HIV in the US vs. the rest of the world

Worldwide, there were 37.9 million people living with HIV in 2018, according to the World Health Organization (WHO) (WHO, 2019). HIV prevalence varies significantly by region and country. For example, in the US, approximately 0.3% of the population is infected with HIV, while some countries in Southern Africa have prevalence rates that exceed 20%. 25.7 million of those infected with HIV are living in Africa. The lowest HIV rates in the world are countries with approximately 1 in 1,000 people infected. 

New infections continue to be a problem, as well. In 2018, there were approximately 1.7 million new infections worldwide. While in the US, MSM are the population with the highest rates of HIV infection, 52% of people infected worldwide are female, and heterosexual contact is actually the predominant method of HIV transmission.

What are the signs and symptoms of HIV?

Things would be simpler if people with HIV had signs and symptoms. People would be diagnosed earlier in the course of the disease, and transmission rates might be lower if fewer people went untreated. Unfortunately, HIV is usually asymptomatic for most of its course, but it can still be transmitted during this time. In fact, 90% of transmissions in the US are from those who don't even know they're infected (Gunthard, 2016).

There are three stages of HIV infection:

  1. Acute HIV Infection: About 2–4 weeks after an infection, a person may develop a flu-like illness, including fever, rash, headaches, sore throat, body aches, and swollen lymph nodes. Some people have no symptoms at all. During this time, the viral load is very high, and the risk of transmission from the newly infected person is high. Many people will just think they have a garden variety viral illness, which becomes incorrectly confirmed when they start feeling better within a couple of weeks. During this time, the body has not yet mounted an antibody response, but newer HIV tests may still be positive in this timeframe. 

  2. Chronic HIV Infection: After the body mounts an immune response, the viral load decreases, but the virus persists in the body. During this period, HIV continues to replicate, but there are no symptoms. People usually stay in this phase for years, even up to a decade or more, and with treatment, this stage can last indefinitely. Even though there are no symptoms at this stage, the virus can still spread. Over time, the body's immune system gets damaged until people reach the third stage of the disease.

  3. AIDS: This stage is defined in one of two ways. A CD4 count of <200 cells/mm³ or an AIDS-defining illness. 

What are the signs and symptoms of AIDS?

The signs and symptoms of AIDS are often related to opportunistic infections people get when their immune systems are weakened. Some examples include:

  • Rapid weight loss

  • Recurring fever or profuse night sweats

  • Extreme fatigue

  • Swelling of the lymph nodes in the armpits, groin, or neck

  • Chronic diarrhea

  • Sores of the mouth, anus, or genitals

  • Pneumonia (this can be PJP pneumonia or community-acquired bacterial pneumonia)

  • Red, brown, pink, or purplish lesions on or under the skin or inside the mouth, nose, or eyelids 

  • Memory loss, depression, and other neurologic disorders

These symptoms can be caused by other diseases also, and it's important that you be evaluated by a healthcare professional if you are experiencing any of these.

HIV testing

HIV testing has gone through different phases since they were first introduced in 1985. Currently, there are three main types of HIV tests in use. There are also recommended tests for people who have already been diagnosed with HIV.

There are three basic types of HIV tests. These include:

Antibody tests

These were the original tests available for HIV. They test for the presence of antibodies against HIV that are made by the body. It can take up to 12 weeks until the body makes enough antibodies to turn these tests positive, so there may be false positives during this time. This period is called the "window period." These tests can be done by drawing blood from a vein or with a finger prick. There is also an at-home test available, called Oraquick, that tests for the antibodies with an oral swab and does not require a blood draw (OraQuick, n.d.).

4th generation HIV testing

This tests for antibodies that the body makes in response to the HIV virus as well as a protein (antigen) that the virus makes called the p24 antigen. This is the preferred test for HIV screening and diagnosis. One reason is that these tests usually turn positive earlier (2–6 weeks) after infection than antibody tests. However, it is still recommended that you get retested after three months if you are worried about a potential exposure to HIV. It usually requires drawing blood from a vein, but these can also be done with a finger prick, although they may take longer to turn positive.

RNA tests

These tests look for HIV RNA (genetic material) in the blood and usually turn positive 1–4 weeks after infection. This is also the test used to measure the viral load after someone is diagnosed with HIV. While these tests turn positive early after infection, they are also costly and are usually not recommended for screening or diagnostic purposes.

What to expect when taking an HIV test

Depending on the type of test you undergo, you may have blood drawn from a vein or a finger stick, or you may just do an oral swab. You may also be tested for other STIs. This may be done through urine testing or through any combination of penile, vaginal, cervical, or throat swabs, depending on the type of sex you have and your individual risk factors.

If you do a rapid test, you may get the results in as little as 20 or 30 minutes. Some tests are sent to the laboratory for analysis and take days for results to be reported. If you are having the test performed by a healthcare provider or an HIV counselor, they will likely counsel you on safe sex practices and safe use of injection drugs if you use injection drugs regardless of the outcome of the test.

Outcome and accuracy of HIV tests

Modern HIV tests are very accurate, but there are a few things to keep in mind.

  1. It's possible to test negative and still have HIV. This usually happens if you get tested during the "window period," and it's the reason that healthcare professionals recommend repeat testing after three months if you had an exposure that you are concerned about. False negatives more than 12 weeks after infection are extremely rare. This is especially true for 4th generation tests that look for both antibodies to HIV and the p24 antigen. People with risk factors for HIV should generally get tested using 4th generation tests when possible as they miss fewer early infections.

  2. It's possible to test positive and not have HIV, but it isn't likely. This is more common with antibody only tests, and it's the reason these tests require confirmation before a diagnosis can be made.

  3. RNA tests may be used for diagnosis under certain special circumstances. Examples would be if someone had an "indeterminate" result or if a person had exposure to HIV-2, the type of virus that is mostly found in Western Africa. 

As you can see, HIV testing can get pretty complicated pretty quickly, which is why it's a good idea to talk to a healthcare professional about testing.

Modern HIV treatment

Modern HIV treatment is usually accomplished with a combination of 3 or 4 drugs that are active against HIV. Over the years, these combination drug regimens have been called HAART (short for highly active antiretroviral therapy), cART (short for combination antiretroviral therapy), or just ART (short for antiretroviral therapy). These days, the term ART is the most commonly used. Combining drugs is necessary because it was found that the virus was able to rapidly mutate if only one or two drugs active against HIV were used. In 2019, the first complete two-drug combination was approved by the FDA to treat HIV in certain people (FDA-b, 2019). However, most HIV regimens still consist of 3 or 4 drugs.

How does HIV treatment work?

HIV regimens use drugs that have different mechanisms for preventing the HIV virus from multiplying. Together, these drugs can keep the level of the virus so low in the blood that it cannot be measured through HIV RNA blood tests. While this does not mean that the person is no longer infected, it does mean that the virus is prevented from further infecting the body's immune cells and destroying the immune system. This means that people who are properly treated for HIV infection can stay in the chronic, asymptomatic stage for a long time, and they may never progress to AIDS. 

Studies of gay and heterosexual couples have shown that when HIV positive people are treated to full viral suppression, the risk of transmission through sexual contact is essentially zero. This is sometimes referred to as "treatment as prevention" because treating those who are infected decreases the risk of transmission to their uninfected partners. It is still possible to transmit the virus through sharing needles or from mother to child when viral levels are undetectable.

What is the life expectancy of people with HIV who receive treatment?

In the '80s and early '90s, HIV had a very poor prognosis, and most people died within a few years of their diagnosis. But now we have probably the best news yet! Several recent studies done in various populations have shown that some people with HIV who are on proper treatment can have life expectancies that approach those of the general population (May, 2014). Several factors affect the prognosis of someone living with HIV.

These include:

  • How advanced the disease is when diagnosed

  • How well you respond to treatment (including viral load and CD4 count)

  • Whether you have had HIV-related illnesses in the past

  • The presence of other chronic conditions and injection drug use

The good news is that modern drug therapy significantly prolongs life for people with HIV, and those who get diagnosed early and start ART right away can live fairly normal lives so long as they faithfully take their medicine and stay plugged into the healthcare system.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

October 03, 2019

Written by

Tzvi Doron, DO

Fact checked by

Mike Bohl, MD, MPH, ALM

About the medical reviewers

Dr. Tzvi Doron is Board Certified in Family Medicine by the American Board of Family Medicine.

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.