HIV symptoms vary substantially according to the stage of infection, and some people have no noticeable symptoms for years. Acute HIV infection, which occurs shortly after acquisition, can produce a flu-like or glandular-fever-like illness in some people, usually within the first few weeks. Possible symptoms include fever, sore throat, swollen lymph nodes, rash, headache, muscle aches, joint pains, fatigue, night sweats, mouth ulcers, and diarrhoea. These symptoms are non-specific and overlap with many common viral illnesses, so they cannot establish that HIV infection has occurred. Some people experience no acute illness at all. Consequently, symptoms are not a reliable substitute for HIV testing after a potentially significant exposure.
During acute infection, HIV replication can be extremely high as the virus establishes infection throughout lymphoid and other tissues. The immune system responds by producing innate and adaptive immune responses, and this period can generate systemic symptoms. CD4 T-cell numbers can temporarily fall, while HIV RNA levels rise markedly. The acute illness may last days or weeks and then resolve as the immune response partially controls viral replication.
Because the symptoms resemble influenza, glandular fever, COVID-19, other viral infections, and numerous non-infectious conditions, people cannot diagnose acute HIV from symptoms alone. The appropriate way to determine whether HIV has been acquired is through appropriately timed testing, with repeat or additional testing when required because very recent infection may fall within a diagnostic window period.
After acute infection, untreated HIV can enter a chronic phase in which many people feel completely well. This period can last for years, although HIV remains biologically active and continues to affect the immune system. A person can therefore have HIV without experiencing fever, pain, weight loss, or other obvious symptoms. Some individuals develop persistent generalised lymphadenopathy, meaning enlarged lymph nodes in several regions, but this is not universal and is not specific to HIV.
The absence of symptoms does not mean that the infection has disappeared. Untreated HIV continues to replicate and can progressively reduce immune competence even while the person appears healthy. This asymptomatic phase is a major reason routine testing and testing after relevant exposure are important.
As HIV progresses without effective treatment, immune deficiency can produce more persistent or severe symptoms. Possible manifestations include unexplained weight loss, recurrent fever, prolonged diarrhoea, drenching night sweats, persistent swollen lymph nodes, severe or recurrent infections, oral fungal infection such as candidiasis, shingles, recurrent bacterial infections, and certain skin abnormalities. The pattern depends on the degree of immune suppression and the infections or malignancies that develop.
These symptoms are not specific to HIV and can arise from many other medical conditions. Their significance lies in the combination, persistence, severity, and clinical context rather than any individual symptom. Modern antiretroviral therapy can prevent progression to severe immune deficiency when diagnosis and treatment occur appropriately.
Advanced untreated HIV can lead to AIDS, in which severe immune suppression permits opportunistic infections and certain cancers to develop. Examples include Pneumocystis jirovecii pneumonia, cryptococcal disease, toxoplasmosis affecting the brain, oesophageal candidiasis, certain mycobacterial infections, cytomegalovirus disease, Kaposi sarcoma, and some lymphomas. The exact definition of AIDS uses specific clinical conditions and/or a severely reduced CD4 count, depending on the diagnostic framework. These conditions are consequences of profound immune dysfunction rather than ordinary symptoms of every HIV infection. A person who starts effective treatment before advanced immune deficiency may never develop AIDS. The development of serious opportunistic disease is therefore not an inevitable stage of HIV infection in the era of effective antiretroviral therapy.
Symptoms alone cannot distinguish HIV from many other conditions. Fever, fatigue, swollen glands, rash, diarrhoea, night sweats, weight loss, and sore throat can occur with ordinary viral infections, autoimmune disorders, cancers, medication reactions, and numerous other diseases. Conversely, someone with HIV may have none of these symptoms. Testing is therefore essential when there has been a potentially significant exposure or when a clinician considers HIV relevant to a person's presentation. Different tests have different window periods, so a negative result obtained immediately after exposure cannot necessarily exclude infection. Healthcare professionals can select the appropriate test and timing based on the exposure and available testing technology.
Effective treatment changes the symptom profile and long-term course of HIV. Antiretroviral therapy suppresses viral replication, allows immune recovery in many people, and substantially reduces the risk of opportunistic infections and AIDS-related complications. A person receiving effective treatment may have no HIV-related symptoms and may have a life expectancy approaching that of people without HIV, depending on when treatment starts and other health factors. Treatment does not generally eliminate the virus from the body, so therapy must normally continue to maintain viral suppression. Sustained undetectable viral load also means that HIV is not sexually transmitted, an established principle known as U=U.
The most important practical distinction is between symptoms that may occur with HIV and symptoms that can diagnose HIV. No symptom pattern is sufficiently specific to confirm or exclude HIV infection. Acute infection can resemble a common viral illness, chronic infection can be asymptomatic, and advanced untreated infection can produce severe immune-related disease. Anyone concerned about a possible recent exposure should seek appropriate HIV testing rather than waiting for symptoms.
If the exposure occurred recently enough to fall within the period in which post-exposure prophylaxis may be beneficial, urgent medical advice is important because PEP is time-sensitive. Early diagnosis also permits rapid initiation of antiretroviral treatment, which protects the individual's immune system and, once viral suppression is achieved and maintained, prevents sexual transmission to partners.
