HIV: From Testing to Treatment and U=U

A 26-year-old man attends a sexual health service after developing fever, a sore throat, a widespread rash and marked fatigue. He initially thought he had a viral illness, but during the consultation he mentions condomless sex with a new partner about three weeks earlier. He has no significant past medical history and asks whether the symptoms could be related to a sexually transmitted infection.

What might his symptoms suggest?

There are many possible causes of fever, rash and sore throat, so this presentation is not diagnostic of HIV. The timing and sexual history do, however, mean that acute HIV infection should be considered and an HIV test offered alongside assessment for other possible causes.

Some people develop an illness during early HIV infection, often called seroconversion illness or acute HIV syndrome. Fever, sore throat, rash, lymphadenopathy, headache, myalgia and fatigue can occur, but the presentation is variable and some people have few or no symptoms. That is one reason HIV cannot be diagnosed or excluded from symptoms alone.

Human immunodeficiency virus (HIV) is a virus that primarily targets the immune system, particularly CD4 T lymphocytes. HIV and acquired immune deficiency syndrome (AIDS) are not interchangeable terms. HIV is the infection. AIDS describes advanced HIV disease in which immune suppression has become severe and particular opportunistic infections, malignancies or other AIDS-defining conditions may occur. Effective antiretroviral therapy (ART) can prevent progression to this stage.

There are two main types. HIV-1 causes the great majority of infections worldwide and is the type most commonly encountered in UK practice. HIV-2 is much less common, generally progresses more slowly and has some important differences in treatment. The replication cycle described below primarily refers to HIV-1.

What is happening and why?

To understand HIV treatment, it helps to follow what the virus does when it reaches a susceptible CD4 cell. On the viral envelope is a protein called gp120, which binds to the CD4 receptor on the cell surface. HIV then needs a co-receptor, most commonly CCR5. CCR5 is a normal human chemokine receptor involved in immune-cell signalling; HIV has evolved to use it to gain entry. Some viral variants use another co-receptor called CXCR4. Once these attachments have formed, another viral protein, gp41, helps the viral envelope fuse with the cell membrane.

HIV carries its genetic information as RNA, but the CD4 cell stores genetic information as DNA. The viral enzyme reverse transcriptase converts the HIV RNA into DNA. That viral DNA then moves into the nucleus, where integrase inserts it into the person's cellular DNA. Once integrated, it is called a provirus. The infected cell can now use that viral genetic material to produce new viral RNA and proteins.

New HIV components assemble near the cell membrane and bud from the cell. A third viral enzyme, protease, cuts viral proteins into their functional forms so that the newly produced virus matures and can infect another susceptible cell. The names of several antiretroviral drug classes suddenly make more sense when you can picture this cycle: reverse transcriptase inhibitors, integrase inhibitors and protease inhibitors interrupt different stages of viral replication.

ART can suppress new rounds of replication extremely effectively, but it does not remove every infected cell. Some long-lived cells contain integrated HIV DNA without actively producing large amounts of virus. These cells contribute to the latent reservoir. If treatment is stopped, virus can become active again and the viral load can rise. This is why an undetectable viral load means treatment is successfully suppressing HIV, not that HIV has been eradicated from the body. (BHIVA, 2025)

During acute infection, viral replication can be rapid and the amount of HIV in the blood rises sharply. The immune response then brings that initial peak partly under control, but without treatment HIV persists. Over time, continuing infection and immune activation can reduce the CD4 T-cell population. CD4 cells help coordinate adaptive immune responses, so substantial depletion leaves the person increasingly vulnerable to infections and malignancies that a functioning immune system would usually control.

HIV remains an important part of UK healthcare, but modern treatment has transformed its prognosis. Surveillance is reported separately across the four nations. In Scotland, Public Health Scotland estimated that 6,669 people were living with HIV at the end of 2025. An estimated 94% were diagnosed; among diagnosed people, 92% had received ART during the reporting period and 98% of those receiving ART had a suppressed viral load. There were 132 first-ever HIV diagnoses in Scotland in 2025, and 39 were diagnosed at a late stage. These are Scottish surveillance figures rather than UK-wide totals, but they show both how effective modern HIV care can be and why timely testing still matters. (Public Health Scotland, 2026)

What else would you want to know?

Return to our patient. The combination of a non-specific viral-type illness and a recent exposure means the history needs to establish both his likelihood of HIV exposure and whether another diagnosis could explain his symptoms.

Ask when the possible exposure occurred and what type of sexual contact took place, including vaginal, anal or oral sex and whether condoms were used. Explore recent and previous partners, previous HIV and STI testing, use of pre-exposure prophylaxis (PrEP), any previous post-exposure prophylaxis (PEP), and whether a partner is known to be living with HIV. If a partner is living with HIV, their treatment and viral suppression are relevant because sustained viral suppression prevents sexual transmission.

HIV is not transmitted only through sex. Ask about injecting drug use and shared injecting equipment where relevant, previous significant blood exposure, and occupational exposure such as a sharps injury. Pregnancy and infant feeding need their own clinical assessment because prevention and management pathways differ from sexual transmission.

The symptoms also deserve a normal clinical history rather than being forced into an HIV diagnosis. Ask about duration and progression of fever, rash, sore throat, lymph-node enlargement, gastrointestinal or neurological symptoms, medications, travel and other infection exposures. A non-judgemental approach is essential. The purpose of a sexual history is to understand exposure and choose appropriate tests, not to make assumptions about identity, relationships or behaviour.

What investigations are recommended?

Our patient's possible exposure was around three weeks ago, so the timing of testing needs explaining carefully. A laboratory fourth-generation HIV test detects both antibodies to HIV and p24 antigen, a viral capsid protein that can become detectable before the antibody response is fully established. UK guidance gives fourth-generation laboratory testing a 45-day window period, by which time 99% of infections will be detected. A negative result before the end of the relevant window period therefore needs to be interpreted in relation to the timing of exposure and may require repeat testing. (BHIVA/BASHH/BIA, 2020)

If HIV is diagnosed, the assessment moves beyond a positive or negative test. HIV viral load measures HIV RNA in the blood, usually reported as copies per millilitre. It tells us about the amount of circulating virus and becomes one of the main ways of assessing response to treatment. The CD4 count measures the immune-cell population HIV has been affecting. These results answer different questions, so they should not be read as two versions of the same measurement.

Before and around treatment initiation, specialist HIV care also considers resistance testing and baseline investigations such as renal and liver function, hepatitis status, other STI testing and other investigations appropriate to the individual. The exact pathway belongs within specialist HIV services and current BHIVA guidance.

How could HIV be managed?

HIV is managed with antiretroviral therapy (ART). Modern ART combines active antiretroviral drugs so that HIV replication is suppressed at more than one point in its life cycle. BHIVA recommends ART for people living with HIV, with the regimen selected according to factors including resistance, drug interactions, renal function, hepatitis B status, pregnancy and individual circumstances. Current first-line approaches commonly include an integrase inhibitor. (BHIVA, 2025)

Once effective treatment begins, viral load can fall quickly. CD4 recovery is a different biological process and may take longer, so a rapidly falling viral load with a more gradual improvement in CD4 count can be entirely consistent with successful treatment.

When the amount of circulating HIV falls below the laboratory assay's quantification threshold, the result may be described as undetectable. This does not mean HIV has disappeared. Integrated HIV remains within the latent reservoir, which is why ART continues even when the person feels well and their viral load has been suppressed for years.

Undetectable = Untransmittable

This is one of the biggest changes in modern HIV care. A person can be living with HIV, take effective antiretroviral therapy (ART) consistently and have the amount of circulating virus fall so low that their viral load becomes undetectable. When viral suppression is sustained below 200 copies/mL, the evidence shows zero risk of sexual HIV transmission. This is U=U: Undetectable = Untransmittable. Large studies involving couples in which one partner was living with HIV found no linked sexual transmissions while viral suppression was maintained. (BHIVA)

The number can be confusing because a laboratory may describe a viral load below a lower threshold, often around 50 copies/mL, as undetectable. That laboratory threshold describes what the particular assay can reliably quantify. The 200 copies/mL U=U threshold comes from evidence about sexual transmission. The person still has HIV and needs to continue ART because integrated HIV remains within the latent reservoir, but while viral suppression is maintained they do not sexually transmit HIV.

This also changes the conversation with partners. An HIV-negative partner does not need PrEP to protect them from sexual HIV transmission from a partner who is maintaining U=U, although PrEP may still be appropriate if they have other potential HIV exposures. Condoms may still be used for contraception and to reduce transmission of other sexually transmitted infections. U=U applies specifically to sexual transmission and should not simply be transferred to situations such as occupational blood exposure or infant feeding, which have separate evidence and guidance.

How can HIV acquisition be prevented?

Pre-exposure prophylaxis (PrEP) is different from ART used to treat HIV. PrEP is taken by someone who does not have HIV to reduce the chance of acquiring the virus if they are exposed. Current UK guidance includes oral PrEP containing the antiretroviral medicines tenofovir disoproxil and emtricitabine, as well as long-acting injectable cabotegravir for appropriate people. Oral PrEP can be taken using different dosing approaches, including daily and, for eligible people in appropriate circumstances, event-based dosing. The right option depends on the person's anatomy, type and timing of potential exposure, clinical circumstances and current guidance. (BASHH/BHIVA, 2025)

It helps to keep the roles of these medicines separate. ART treats a person who is living with HIV and can achieve U=U. PrEP is used before potential exposure by a person who does not have HIV. PEP is used after a potential exposure. They all use antiretroviral medicines, but they are being used for different clinical purposes.

Post-exposure prophylaxis (PEP) is used after a potential exposure. It should be started as soon as possible, preferably within 24 hours, and is not recommended when more than 72 hours have passed. The course is normally continued for 28 days. PEP can be relevant after sexual exposure, injecting exposure or an occupational blood exposure. (BASHH/BHIVA, 2021)

For a student nurse, a sharps injury is the situation in which you may encounter this pathway directly. Wash or manage the exposure according to local policy, report it promptly and access the occupational-exposure pathway without delay. You are not expected to decide independently whether PEP is required. The clinical assessment considers the nature of the exposure, information about the source and other blood-borne viruses including hepatitis B and hepatitis C.

What should we explain to the patient?

A new HIV diagnosis can carry fears that are based on what HIV meant decades ago rather than what it means with modern treatment. Our patient needs accurate information without false reassurance. HIV is a chronic infection that requires ongoing care and treatment, but effective ART can suppress the virus, protect the immune system and allow people living with HIV to live long, healthy lives.

Explain viral load and CD4 count in language he can use. Viral load tells us how much HIV is circulating and whether treatment is suppressing replication. CD4 count gives information about the immune system. Explain that an undetectable viral load is an excellent treatment outcome but does not mean the virus has been removed from the body, so ART should not be stopped simply because the result is undetectable.

U=U should be part of that conversation rather than something the patient has to discover elsewhere. Sustained viral suppression means HIV is not sexually transmitted. That information can affect relationships, sexual wellbeing, conception decisions and the stigma a person may feel after diagnosis.

Partner notification, testing for other STIs and discussion of PrEP for HIV-negative partners may be appropriate depending on viral load, timing and individual circumstances. Confidentiality and disclosure should be handled carefully and according to professional and specialist guidance rather than making assumptions about who the patient should tell.

What could happen if HIV is not appropriately managed?

Without effective ART, continuing HIV replication can progressively damage the CD4 T-cell population. As immune function declines, infections that are normally controlled can become severe. Conditions encountered in advanced HIV include Pneumocystis jirovecii pneumonia, oesophageal candidiasis, cryptococcal disease and tuberculosis, while the risk of some malignancies also rises.

This is the context in which AIDS belongs. It is not an inevitable next stage for someone diagnosed with HIV. It describes advanced disease associated with severe immune suppression and particular AIDS-defining illnesses. Early diagnosis, ART and continued engagement with HIV care can prevent progression to advanced disease.

For nurses outside specialist HIV services, HIV will often be one part of a patient's medical history rather than the reason for admission. Someone living with HIV may be in front of you because they have appendicitis, pneumonia, a fracture, are pregnant or need planned surgery. Check their ART and do not casually omit or stop it. New medicines may interact with antiretrovirals, so interactions should be checked appropriately.

HIV alone is not an indication for side-room isolation or separate equipment. Use standard infection prevention precautions and safe sharps practice as you would for every patient. Avoid assumptions about how the person acquired HIV or about their relationships. A patient with sustained viral suppression and good immune recovery is clinically very different from someone with untreated viraemia and advanced immune suppression.

References

British HIV Association (BHIVA) (2025) BHIVA guidelines on antiretroviral treatment for adults living with HIV-1 2022: 2025 interim update. Available at: BHIVA HIV-1 treatment guidelines.

British HIV Association (BHIVA) (2021) British HIV Association guidelines for the management of HIV-2 2021. Available at: BHIVA HIV-2 guidelines.

British HIV Association, British Association for Sexual Health and HIV and British Infection Association (2020) Adult HIV testing guidelines 2020. Available at: UK HIV testing guidelines.

British Association for Sexual Health and HIV and British HIV Association (2021) UK Guideline for the use of HIV Post-Exposure Prophylaxis 2021. Available at: UK PEP guidelines.

British Association for Sexual Health and HIV and British HIV Association (2025) Guidelines on the use of HIV pre-exposure prophylaxis (PrEP) 2025. Available at: UK PrEP guidelines.

British HIV Association (BHIVA) (2025) Guidelines on the management of HIV in pregnancy and the postpartum period 2025. Available at: BHIVA pregnancy guidelines.

British Association for Sexual Health and HIV and British HIV Association (2026) Joint guidelines for the sexual and reproductive health of people living with HIV 2026. Available at: BASHH/BHIVA sexual and reproductive health guidelines.

Public Health Scotland (2026) HIV in Scotland: update to 31 December 2025. Available at: Public Health Scotland.