Human immunodeficiency virus, better known as HIV, has changed dramatically from the disease first recognized more than four decades ago. HIV remains a major global public health challenge, but advances in testing, prevention, and antiretroviral treatment have transformed what an HIV diagnosis means.
With effective treatment, people living with HIV can live long and healthy lives. Treatment can suppress the amount of virus in the blood to an undetectable level, protecting the immune system and preventing progression to AIDS. Crucially, a person who takes effective treatment and maintains an undetectable viral load does not sexually transmit HIV. This principle is known as U=U: Undetectable = Untransmittable.
HIV, however, has not disappeared. The World Health Organization estimates that approximately 41 million people were living with HIV at the end of 2025, while about 1.2 million people acquired HIV during that year.
Understanding how HIV is actually transmitted is essential not only for preventing infection but also for challenging misconceptions and stigma surrounding people living with HIV.
What Is HIV?
HIV stands for human immunodeficiency virus.
It is a virus that attacks the immune system, particularly important white blood cells involved in protecting the body against infections.
Without treatment, HIV gradually damages immune function. As immune defenses become weaker, the body becomes increasingly vulnerable to infections and certain cancers that a healthy immune system would normally be better able to control.
HIV infection is currently considered a lifelong condition because available treatments suppress the virus rather than completely eliminating it from the body.
However, modern antiretroviral therapy can reduce HIV replication so effectively that the immune system can remain healthy and the amount of virus circulating in the blood can become undetectable on standard laboratory tests.
This means that HIV today is very different from untreated HIV during the early decades of the epidemic.
What Is AIDS?
HIV and AIDS are related, but they are not the same thing.
HIV is the virus.
AIDS stands for acquired immunodeficiency syndrome and represents the most advanced stage of HIV infection.
Without effective treatment, HIV can progressively weaken the immune system until serious opportunistic infections, cancers, or other AIDS-defining conditions develop.
Modern treatment can prevent this progression.
HIV.gov describes three broad stages of untreated infection: acute HIV infection, chronic HIV infection, and AIDS. With effective treatment, most people living with HIV do not progress to AIDS.
Therefore, someone who has HIV should not automatically be described as having AIDS.
What Does HIV Do to the Immune System?
HIV particularly targets immune cells known as CD4 cells.
These cells help coordinate immune responses against infections.
The virus enters susceptible cells and uses their biological machinery to reproduce. Over time, untreated infection can reduce the number and function of CD4 cells.
As immune function deteriorates, infections that would normally be controlled can become more severe.
Tuberculosis is an especially important infection among people with advanced HIV globally. Other serious illnesses can include cryptococcal meningitis, severe bacterial infections, lymphoma, and Kaposi sarcoma.
Antiretroviral treatment interrupts HIV replication and allows the immune system to recover or remain strong.
Early Symptoms of HIV
One of the most important facts about HIV is that symptoms cannot reliably tell someone whether they have the infection.
Some people develop an illness shortly after acquiring HIV, while others experience no noticeable symptoms.
When acute symptoms occur, they often develop approximately two to four weeks after infection.
The illness can resemble influenza or another common viral infection. Fever, sore throat, rash, swollen lymph nodes, fatigue, night sweats, muscle aches, chills, and mouth ulcers may occur.
According to HIV.gov, approximately two-thirds of people experience some flu-like symptoms during acute HIV infection.
These symptoms are extremely nonspecific.
Having a fever, sore throat, rash, or swollen glands does not mean that someone has HIV. Numerous common infections can produce identical symptoms.
Testing, rather than symptoms, is the only reliable way to determine HIV status.
Acute HIV Infection
Acute HIV infection is the earliest stage of the disease.
During this period, HIV is reproducing rapidly and the viral load can be very high. This makes transmission more likely when exposure occurs.
The immune system begins responding to the infection, which is why some people develop the flu-like illness associated with acute HIV.
However, a person may not yet realize they have HIV.
This creates an important prevention challenge because someone can transmit HIV without knowing they have acquired it.
If a person has experienced a potential HIV exposure and subsequently develops flu-like symptoms, they should seek appropriate testing rather than attempting to diagnose themselves based on symptoms.
Chronic HIV Infection
After the acute phase, HIV typically enters a chronic stage.
Without treatment, the virus remains active but may reproduce at lower levels. Someone can feel completely healthy during this period.
The absence of symptoms does not mean that the virus has disappeared.
Untreated chronic infection can continue for years while gradually damaging the immune system.
HIV.gov notes that untreated chronic HIV can sometimes last 10 to 15 years, although progression varies between individuals.
With effective antiretroviral therapy, however, people can remain in excellent health and avoid progression to AIDS.
Symptoms of Advanced HIV and AIDS
When HIV is untreated and immune damage becomes severe, more significant illness can develop.
Persistent or recurrent fever, substantial unexplained weight loss, prolonged diarrhea, night sweats, extreme fatigue, persistent swollen lymph nodes, pneumonia, and other recurrent or unusual infections can occur.
Certain cancers and neurological problems may also become more likely.
However, none of these symptoms alone diagnoses AIDS.
Many other medical conditions can cause similar problems.
Healthcare professionals use clinical findings, laboratory tests, CD4 measurements, viral load, and the presence of certain AIDS-defining illnesses when assessing advanced HIV disease.
How Is HIV Transmitted?
HIV transmission requires exposure to certain body fluids containing the virus.
Important fluids include blood, semen, vaginal fluids, rectal fluids, and breast milk. Transmission can also occur from a pregnant person to their baby during pregnancy, childbirth, or breastfeeding.
Sexual transmission is one of the main routes globally.
HIV can also be transmitted through sharing needles, syringes, or other injecting equipment contaminated with infected blood.
Transmission through blood transfusion is possible when blood has not been appropriately screened, although modern blood-screening systems have made this extremely uncommon in countries with strong blood-safety programs.
Occupational exposure can occasionally occur in healthcare environments, such as through a contaminated needlestick injury.
HIV and Sexual Transmission
HIV can be transmitted during vaginal or anal sex when one person has transmissible HIV.
The probability of transmission varies according to multiple factors, including viral load, the type of sexual exposure, whether condoms or PrEP are used, and whether other sexually transmitted infections are present.
Anal sex generally carries a greater biological risk of HIV transmission than vaginal sex when other factors are equal because rectal tissue is particularly susceptible to microscopic injury.
Oral sex presents a substantially lower HIV risk than vaginal or anal intercourse.
Most importantly, treatment changes the equation completely.
A person living with HIV who takes effective antiretroviral therapy and maintains an undetectable viral load will not transmit HIV through sex.
What Does U=U Mean?
U=U means Undetectable = Untransmittable.
This is one of the most important advances in HIV medicine and public health.
When antiretroviral therapy suppresses HIV to an undetectable level and that suppression is maintained, there is zero risk of sexual HIV transmission.
This conclusion is supported by extensive scientific evidence and is recognized by major health authorities, including WHO and U.S. HIV guidelines.
U=U benefits both physical and psychological health.
It means that effective HIV treatment protects the person living with HIV while also protecting their sexual partners from HIV transmission.
People beginning treatment need follow-up viral-load testing to establish that suppression has been achieved and maintained. Until this has been confirmed, additional prevention methods may be recommended.
HIV Is Not Spread Through Everyday Contact
Misunderstanding this point has contributed enormously to HIV stigma.
HIV is not transmitted through ordinary social contact.
You cannot acquire HIV from hugging someone, shaking their hand, sharing a meal, drinking from the same glass, sharing a toilet, or simply living or working with someone who has HIV.
WHO specifically confirms that HIV is not transmitted through everyday activities such as kissing, hugging, shaking hands, or sharing food or personal objects.
People living with HIV do not pose a danger to colleagues, classmates, friends, or family members through normal daily interaction.
Can HIV Spread Through Kissing?
Ordinary kissing does not transmit HIV.
Saliva is not considered a route of HIV transmission during normal social or intimate contact.
The presence of HIV in certain bodily fluids does not mean that every bodily fluid can efficiently transmit the virus.
This distinction matters because fear surrounding casual contact has historically contributed to discrimination against people living with HIV.
There is no reason to avoid ordinary physical affection, shared living spaces, meals, or normal social contact with someone because they have HIV.
Can Mosquitoes Transmit HIV?
No.
HIV is not transmitted through mosquito bites.
Mosquitoes do not inject another person’s blood into someone when they bite, and HIV cannot reproduce inside mosquitoes in the way mosquito-borne viruses or parasites do.
If mosquitoes could efficiently transmit HIV, patterns of infection would look completely different from what epidemiologists observe.
Living in an area with many mosquitoes does not create an HIV transmission risk.
HIV and Pregnancy
Without treatment, HIV can be transmitted from parent to child during pregnancy, childbirth, or breastfeeding.
Modern antiretroviral treatment has dramatically changed this situation.
Effective ART during pregnancy protects the health of the pregnant person while greatly reducing the likelihood of transmission to the baby.
WHO reports that approximately 88% of pregnant women living with HIV globally received antiretroviral medicines in 2025.
Pregnancy involving HIV requires specialist care because treatment, viral-load monitoring, delivery planning, infant medication and testing, and infant-feeding recommendations may need to be coordinated.
With appropriate treatment and medical care, people living with HIV can have healthy pregnancies and children without HIV.
How Is HIV Diagnosed?
The only way to know whether someone has HIV is through testing.
Different HIV tests detect different markers of infection.
Some detect antibodies produced by the immune system. Others detect both HIV antigen and antibodies. Nucleic acid tests can detect viral genetic material.
These tests become positive at different times after infection.
This leads to the concept of the window period.
A test performed too soon after exposure may not yet detect infection, even if HIV was acquired.
The appropriate test and timing therefore depend on when the potential exposure occurred.
Healthcare professionals or testing services can advise whether an initial negative result needs to be repeated.
Why Routine HIV Testing Matters
Testing should not be viewed as something only people with symptoms need.
Chronic HIV can remain asymptomatic for years.
Someone can feel completely healthy while living with HIV, which means waiting for symptoms may delay diagnosis substantially.
Early diagnosis allows treatment to begin before significant immune damage occurs.
It also allows viral suppression to be achieved, preventing sexual transmission once the viral load is maintained at an undetectable level.
Testing therefore benefits both individual and public health.
What Happens After a Positive HIV Test?
A positive screening result is followed by appropriate confirmatory testing according to the testing system being used.
Once HIV is confirmed, healthcare professionals assess the person’s overall health and arrange treatment.
Blood tests typically include measurement of viral load, which indicates how much HIV is present in the blood.
CD4 testing provides information about immune-system status.
Additional assessments may include screening for other infections, sexually transmitted infections, hepatitis, tuberculosis, and other conditions depending on the person’s circumstances and location.
Treatment should begin as soon as appropriate rather than waiting for symptoms or significant immune deterioration.
What Is Antiretroviral Therapy?
HIV is treated with antiretroviral therapy, usually abbreviated ART.
Antiretroviral medicines interfere with different stages of HIV’s ability to reproduce.
Effective treatment dramatically reduces the amount of virus in the body.
ART does not currently eliminate all HIV from the body, which means treatment is not considered a cure.
However, it can suppress the virus so effectively that standard blood tests cannot detect the viral load.
This allows the immune system to remain healthy or recover from previous damage.
WHO describes HIV as a manageable chronic health condition when people have access to effective diagnosis, treatment, and care.
When Should HIV Treatment Begin?
Current HIV care emphasizes starting antiretroviral treatment promptly after diagnosis.
Treatment is recommended even when someone feels healthy and has good immune function.
There is no benefit to allowing HIV to damage the immune system before beginning effective therapy.
Early treatment helps preserve immune function, reduces HIV-related illness, and allows the person to achieve viral suppression sooner.
HIV.gov states that HIV medicine is recommended for everyone living with HIV and should be started as soon as possible after diagnosis.
Treatment decisions are individualized according to medical history, other medications, possible drug interactions, pregnancy, kidney and liver function, resistance testing, and other clinical considerations.
Can HIV Be Cured?
There is currently no widely available cure for HIV.
A very small number of people have achieved sustained HIV remission after highly specialized stem-cell transplantation performed for serious cancers. These exceptional cases have provided valuable scientific information but do not represent a practical treatment for most people living with HIV.
For the vast majority of patients, HIV is managed through ongoing antiretroviral treatment.
This distinction is important.
An undetectable viral load does not mean HIV has been eliminated from the body.
Stopping effective treatment can allow the virus to begin reproducing again.
How Long Can Someone With HIV Live?
Modern HIV treatment has transformed life expectancy.
People diagnosed early who receive effective treatment and remain in care can live long, healthy and productive lives.
WHO explicitly describes HIV as a manageable chronic health condition when people have access to effective treatment and care.
Outcomes are influenced by multiple factors, including access to healthcare, timing of diagnosis, treatment adherence, smoking, cardiovascular health, other infections, kidney and liver health, and other medical conditions.
An HIV diagnosis today should therefore not automatically be interpreted as a shortened or severely restricted life.
What Is PrEP?
PrEP stands for pre-exposure prophylaxis.
It involves using antiretroviral medication by a person who does not have HIV to reduce their risk of acquiring it.
PrEP is intended for people whose circumstances place them at meaningful risk of HIV exposure.
Different PrEP options are now available internationally, although availability varies between countries.
WHO currently recognizes several approaches, including oral tenofovir-based PrEP and certain long-acting options.
A healthcare professional can determine whether PrEP is appropriate and arrange the necessary HIV testing and medical monitoring.
PrEP prevents HIV but does not protect against every other sexually transmitted infection, which is why broader sexual-health strategies remain important.
What Is PEP?
PEP stands for post-exposure prophylaxis.
Unlike PrEP, which is taken before potential exposure, PEP is used after a possible HIV exposure.
PEP may be considered after situations such as certain sexual exposures, sharing injecting equipment, or occupational exposure to potentially infected blood.
It is time-sensitive.
Someone who believes they have experienced a significant HIV exposure should therefore seek urgent medical advice rather than waiting to see whether symptoms appear.
WHO recognizes PEP as an important HIV prevention strategy after potential exposure.
Because the actual risk differs greatly between exposures, a healthcare professional assesses whether PEP is indicated.
Condoms and HIV Prevention
Condoms remain an effective component of HIV prevention when used correctly and consistently.
They also reduce the risk of several other sexually transmitted infections and unintended pregnancy.
Modern HIV prevention does not rely on one method.
Depending on circumstances, prevention can involve condoms, HIV testing, PrEP, PEP, sterile injecting equipment, treatment of sexually transmitted infections, and effective ART for people living with HIV.
The most appropriate combination depends on the individual.
Preventing HIV Through Injecting Equipment
Sharing needles, syringes, or other injecting equipment can transmit HIV because contaminated blood can pass directly between people.
Using new sterile equipment for every injection prevents this route of transmission.
Needle and syringe programs are therefore an important public-health intervention.
They can also reduce transmission of other blood-borne infections, including hepatitis C.
WHO includes sterile injecting equipment and harm-reduction strategies among important HIV prevention measures.
HIV and Other Sexually Transmitted Infections
Other sexually transmitted infections can coexist with HIV.
Some STIs can increase susceptibility to HIV transmission by causing inflammation or damage to genital or rectal tissues.
People undergoing HIV testing may therefore be offered screening for other sexually transmitted infections depending on their sexual history and local recommendations.
HIV prevention and broader sexual healthcare should ideally be considered together rather than treating HIV as an isolated issue.
Condoms remain useful because, unlike U=U or PrEP, they can reduce transmission of several other sexually transmitted infections as well.
HIV Treatment and Medication Adherence
Taking HIV medication as prescribed is important for maintaining viral suppression.
Missing treatment repeatedly can allow HIV to reproduce.
In some circumstances, inconsistent treatment can contribute to the development of drug resistance, making certain medications less effective.
However, adherence difficulties should be approached as healthcare problems rather than personal failures.
Side effects, mental health difficulties, unstable housing, medication costs, stigma, travel, work schedules, substance use, or simply forgetting doses can interfere with treatment.
Healthcare teams can often help find practical solutions or alternative regimens.
Modern HIV treatment has become substantially simpler for many people than older treatment regimens.
HIV and Mental Health
An HIV diagnosis can produce a wide range of emotions.
Fear, anger, sadness, uncertainty, or concern about relationships may occur, particularly when someone has outdated ideas about what HIV means.
Modern treatment has dramatically improved the medical outlook, but social stigma can still affect psychological wellbeing.
Accurate information is therefore part of treatment.
Understanding that HIV is manageable and that maintaining an undetectable viral load prevents sexual transmission can fundamentally change how someone views their future relationships and health.
Mental health support, peer groups, counselling, or specialist services can be valuable when needed.
HIV Stigma Remains a Health Problem
HIV stigma is not merely socially unpleasant. It can directly harm health.
People who fear judgment may avoid HIV testing, delay treatment, hide medication, or avoid discussing prevention with partners and healthcare professionals.
Some stigma comes from outdated beliefs dating from a period before effective antiretroviral treatment existed.
Modern evidence makes several facts clear.
HIV is not transmitted through normal everyday contact. People receiving effective treatment can live long and healthy lives. And someone who maintains an undetectable viral load does not sexually transmit HIV.
Public understanding of these facts is an important part of HIV prevention.
HIV Around the World
Despite enormous progress, HIV remains a significant global health challenge.
WHO estimated that 41 million people were living with HIV in 2025, approximately 1.2 million people acquired HIV that year, and around 570,000 people died from HIV-related causes.
Access to treatment has expanded substantially.
WHO reports that around 32.1 million people were receiving HIV treatment in 2025, representing approximately 78% of people living with HIV globally.
These figures demonstrate both the success of modern HIV programs and the remaining gap.
Testing, prevention, treatment access, healthcare inequalities, stigma, and social barriers continue to influence the epidemic.
Frequently Asked Questions
HIV is the virus that attacks the immune system. AIDS is the most advanced stage of untreated or uncontrolled HIV infection. Effective treatment can prevent HIV from progressing to AIDS.
Some people experience fever, sore throat, rash, fatigue, muscle aches, swollen lymph nodes, night sweats, or other flu-like symptoms approximately two to four weeks after infection. Others have no symptoms. Symptoms cannot diagnose HIV; testing is required.
Ordinary kissing does not transmit HIV. HIV is also not spread through hugging, shaking hands, sharing food, or other everyday social contact.
Yes. A person living with HIV who takes effective ART and maintains an undetectable viral load does not transmit HIV through sex. This is U=U.
No. Many people with HIV look and feel completely healthy. The only way to know HIV status is through appropriate testing.
There is currently no generally available cure. Antiretroviral treatment can suppress HIV to undetectable levels and allow people to remain healthy, but treatment does not normally eliminate the virus from the body.
The HIV risk associated with oral sex is much lower than with vaginal or anal intercourse. The precise risk depends on circumstances, but oral sex is not considered a major route of HIV transmission.
No. Mosquitoes do not transmit HIV.
It means antiretroviral treatment has reduced the amount of HIV in the blood below the level detected by the viral-load test being used. Maintaining an undetectable viral load protects health and prevents sexual transmission.
Yes. Effective antiretroviral treatment and specialist medical care can dramatically reduce transmission during pregnancy and childbirth. Pregnancy and infant-feeding management should be planned with the healthcare team.
They should seek medical advice promptly because PEP may be appropriate and is time-sensitive. They should not wait for symptoms before seeking assessment.
No. PrEP is HIV prevention for people who do not have HIV. HIV itself is treated with antiretroviral therapy.
The Bottom Line
HIV is a virus that attacks the immune system, while AIDS represents the most advanced stage of HIV infection. They are not interchangeable terms, and with modern treatment, most people diagnosed with HIV can avoid progressing to AIDS.
HIV can be transmitted through specific bodily fluids, particularly during certain sexual exposures, through contaminated injecting equipment, and from parent to child during pregnancy, childbirth, or breastfeeding. It is not transmitted through ordinary everyday contact, including hugging, shaking hands, sharing food, or simply being around someone living with HIV.
Symptoms are not a reliable method of identifying infection. Some people develop a flu-like illness during acute HIV infection, while others have no noticeable symptoms for years. Testing is the only way to determine HIV status reliably.
Antiretroviral therapy has transformed HIV medicine. Treatment suppresses viral replication, protects the immune system, prevents progression to AIDS, and enables people living with HIV to lead long and healthy lives.
One of the most important messages in modern HIV medicine is U=U: Undetectable = Untransmittable. A person who takes effective treatment and maintains an undetectable viral load has zero risk of sexually transmitting HIV.
Prevention has also advanced substantially. Condoms, regular testing, PrEP before potential exposure, PEP after certain exposures, sterile injecting equipment, and effective treatment for people living with HIV provide multiple ways to prevent transmission.
HIV remains a major global health challenge, but it is no longer the condition it was during the early years of the epidemic. Accurate information, early testing, effective treatment, modern prevention, and the elimination of stigma can allow people living with HIV to protect their health while living full and ordinary lives.
