Diagnosed and undiagnosed HIV infection

In the WHO European Region, new HIV diagnoses are increasing each year, with around 160 000 people newly diagnosed in 2017. 1 In 2015, a total of 2.5 million people were estimated to be living with HIV in the Region – 1.5 million in Eastern Europe and Central Asia and 950 000 in Western and Central Europe. 2

It is estimated that, in the 52 countries which report the relevant data, one in five people living with HIV (20%) is not aware of their infection. The proportion ranges from 13% in the West sub-region, to 17% in the Centre and 24% in the East, with significant variation between countries. 3

When people living with HIV remain undiagnosed, they are at risk of serious illness and death. In addition, it has been estimated that over half of new HIV infections transmitted sexually are from people who are undiagnosed, because without treatment they are more infectious. 4


Adapted from EuroSIDA unpublished data

Life expectancy (BMJ)

Impact of HIV treatment

Antiretroviral therapy has transformed the outlook for people living with HIV: rates of death have fallen dramatically since its introduction in 1996. With early diagnosis and prompt access to treatment, a person diagnosed with HIV can now expect to live almost as long as someone who does not have HIV. 5 However, people in the European Region who are diagnosed late with HIV have a risk of death or progression to AIDS within a year of diagnosis that is up to 13 times higher, on average, than those diagnosed promptly. 6 (This figure varies across the European region.)

In addition, it is now known that effective treatment radically reduces infectiousness and prevents the transmission of HIV. In recent large-scale international studies among couples in which one partner had HIV infection, was on suppressive antiretroviral therapy and did not use condoms, no documented cases of within-couple HIV transmission were found. 7 8

Early diagnosis of HIV is therefore a priority, to enable people to access treatment. WHO HIV treatment guidelines now recommend that antiretroviral therapy should be initiated in all people diagnosed with HIV, however early their infection and whatever their CD4 count.

Late diagnosis

Despite the compelling reasons for early testing and treatment, surveillance data show that over half (53%) of the people living with HIV across Europe are diagnosed at a late stage of infection, increasing the risk of ill health and associated healthcare costs, death and onward HIV transmission. (‘Late’ diagnosis is defined as having a CD4 count of less than 350 cells/mm3 at diagnosis. See more about the natural history of HIV infection here.) The late diagnosis rate varies across Europe – see the map or click here for surveillance report which contains detail by country in Table 14. 9

Although HIV infection occurs more frequently in men who have sex with men (for more on epidemiology click here), people who acquire HIV through heterosexual sex are much more likely to be diagnosed late. (58% of HIV diagnoses in this group were made late in 2017, compared to 39% in men who have sex with men). People who inject drugs are also more likely to be diagnosed late. The probability of late diagnosis increases with age. ECDC estimates that, on average, it takes almost four years (3.8) before an HIV infection is diagnosed and reported. 10 This suggests persistent problems with access to, and uptake of, HIV testing in many countries.

Herpes zoster which can indicate underlying HIV infection (Colm O'Mahony)

Missed diagnoses

One reason for late diagnosis is the missing of opportunities by healthcare professionals to diagnose HIV. People with undiagnosed HIV may experience ill-health without suspecting it is HIV-related. They can present to a range of medical specialties, depending on their condition (for example, to the lung diseases department with tuberculosis, to haematology with immune thrombocytopenic purpura, or to oncology with lymphoma). Yet evidence from several European countries shows that HIV tests are not always offered to people with HIV when they are seen by healthcare professionals in the years before their diagnosis with problems that are potentially HIV-associated. 13 14 15 16 In one recent study, almost 20% of missed HIV diagnoses occurred in people with seborrheic dermatitis/exanthema, more than any other indicator condition. 17 This represents a lost opportunity to diagnose HIV earlier and to avoid significant morbidity and possibly mortality.

In some European countries, it may be important for specialists to diagnose HIV at the first opportunity not only for patients, but also in order to avoid medicolegal and adverse professional consequences.

Why test for HIV? / HIV indicator conditions

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