HIV and other sexually transmitted infections

1. Key messages

The total number of new HIV diagnoses has decreased further in 2020 after a short stagnation between 2018-2019, which might relate to the measures taken by the government against the spread of SARS-COV-2. Nevertheless, a further implementation of the diverse preventive strategies available in Belgium for all people is necessary.

The HIV epidemic in Belgium mainly affects two populations: men who have sex with men (MSM), a group of mainly Belgian or other European nationality, and men and women who have contracted the virus through heterosexual relations, a group mainly from sub-Saharan African origin. On a positive note, a decrease in the number of new infections has been observed in both populations. The rate of new HIV diagnoses is higher in Brussels compared to the other regions, reflecting the fact that HIV infection is mainly an urban phenomenon. In 2020, 69.4% of the new HIV cases were diagnosed in men. Most HIV cases were diagnosed in the 25-49 age group.

Chlamydia is the most common sexually transmitted Infection (STI) in Belgium, followed by condyloma, gonorrhea, and syphilis. The number of reported cases of these three STIs (condyloma is not included in the surveillance) has increased almost threefold in the past 10 years, reflecting more an increase in testing and screening practices, than an increase in incidence. However, an increase in unsafe sexual practices, has been observed among certain groups such as pre-exposure prophylaxis (PreP) users and men who have sex with men (MSM) with dense sexual networks leading to an increase of STIs in those groups.

2. Background

Sexually transmitted infections (STIs) are spread primarily through person-to-person sexual contact. Some STIs, particularly HIV can also be transmitted through blood products and tissue transfer, and from mother to child during pregnancy.

Several STIs, such as HIV, chlamydia, and syphilis, can be present without symptoms, which can facilitate their transmission. STIs may however also lead to severe long-term consequences: HIV is one of the most serious communicable diseases in Europe. It is an infection that can lead to serious morbidity (AIDS) and high costs of preventive treatment and care. Chlamydia and gonorrhea may lead to complications such as infertility, chronic inflammation, and ectopic pregnancy. Untreated syphilis can damage any organ and cause severe neurological complications.

HIV and other STIs are avoidable infections since the transmission is largely preventable by behavioral measures (safe sex, safe injection). Therefore their incidence in a defined population is an indicator of the success/failure of control strategies. Since 2017, the use of pre-exposure prophylaxis to HIV (PrEP) is reimbursed in Belgium. While this may have a positive effect on the incidence of HIV, it may lead to an increase in the incidence of other STIs due to relaxing of vigilance.

The methods of epidemiological surveillance of HIV and other STIs are different, and are therefore described separately.

The epidemiological surveillance of HIV in Belgium dates from 1985 and is carried out by Sciensano on the basis of the registration of the new HIV diagnoses. These data are reported by the seven AIDS reference laboratories that perform all confirmations of positive HIV screening tests. In addition to recording the number of newly diagnosed HIV positive, the laboratories also collect basic epidemiological data on gender, age, nationality, probable route of infection, and clinical stage at the time of diagnosis. Sciensano also collects data on the people living with HIV (PLWH) in Belgium (HIV cohort data) from the AIDS reference laboratories and the HIV reference centers.

Beside the newly diagnosed cases, Sciensano also estimates the number of people living with HIV: those who have not yet been diagnosed [1] and those living with a diagnosed infection. To estimate the undiagnosed population an instrument developed by the European Center for Disease Prevention and Control (ECDC), called the ECDC HIV Modeling Tool [2] is used. And HIV cohort data are used to estimate the number of people living with a diagnosed infection.

ECDC and the WHO Regional Office for Europe jointly coordinate HIV/AIDS surveillance in Europe. The international comparability is however poor, since the national surveillance systems differ in levels of underreporting and reporting delay.

The surveillance of other STIs in Belgium is mainly done via the Sciensano's sentinel network of medical laboratories, which covers about 50% of the laboratories. The STI included in this surveillance are Chlamydia, gonorrhea and syphilis. Since the surveillance of STIs is based on reported cases, the trends do not represent the true incidence. Indeed, since STIs are often asymptomatic, only a part of them are detected and notified. As a result, changes in notification rates can be affected by changes in both the underlying incidence and the proportion of cases being detected (due to an intensification of the screening or to more performant tests). To help interpret these trends, Sciensano compares the evolution of the number of reported cases of chlamydia and gonorrhea to that of the total number of tests for these STIs reimbursed by National Institute for Health and Disability Insurance (RIZIV-INAMI).

The routine surveillance of the laboratory network is completed by the general practitioners network to identify the most important behavioral risk factors and evaluate the impact of prevention campaigns. This network contributes to the knowledge on factors that influence the transmission of STIs.

3. HIV

Situation in 2020

Belgium

In 2020, 725 new diagnoses of HIV infections were made in Belgium (6.3 new diagnoses per 100.000 inhabitants, or on average 2.0 cases a day). Among those, 69.4% were men. 71.3% of the HIV cases were diagnosed in people aged 25-49.

In 2020, 40 new cases of AIDS were notified. 99 deaths were notified among the people infected by HIV. This number includes deaths from any cause (not only related to HIV); from the cause of death register, it appears that HIV is mentioned as underlying cause of deaths in about two third of the deaths where an HIV infection was mentioned.

Number of new reported HIV diagnoses by age and sex, Belgium, 2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]
Regional specificities

In 2020, of the 725 new diagnoses, 240 cases were reported in Brussels, 307 in Flanders, 131 in Wallonia, and 47 cases were of unknown residence.

When accounting for the number of inhabitants, the incidence rates in Flanders and Wallonia are comparable, while the rate in Brussels is much higher. This difference is not surprising since a high HIV prevalence is a common phenomenon in a big city. The Brussels Capital Region can indeed be considered as a big city - with the socio-cultural characteristics of an urban context – while the two other regions mix rural, semi-urban and urban contexts.

Rate of new HIV diagnoses per 100,000 by region, Belgium, 2020
Source: Own calculations from Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]

Trends

Belgium

In 2020, the number of new HIV diagnosis has decreased by 21.7% compared to 2019 and decreased by 41.1% compared to 2012. This decrease in 2020 might relate to the measures taken by the government against the spread of SARS-COV-2.

Between the start of the outbreak in the early 80s and the end of 2020, a total of 33,387 persons were diagnosed with HIV, a total of 5,232 cases of AIDS were reported and 2,951 deaths with HIV were reported. Not all of those deaths were due to HIV. From the cause of death register, it appears, that since 1998, about 1000 deaths were declared having HIV as the underlying cause of death (the code of death for HIV did not exist before).

Number of new diagnoses of HIV, AIDS, and deaths reported, Belgium, 1982-2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]
Regional specificities

Between 2012 and 2020, the number of new HIV diagnoses mainly decreased in Flanders while only slightly decreasing in Wallonia and Brussels. However, it should be noted that the availability of residence data has greatly improved in recent years, from 75% in 2015 to 92% in 2019. The large number of cases from unknown region in the past has resulted in an underestimation of the number of cases in each region, making the observed trends uncertain.

Number of new HIV diagnoses by region, Belgium, 2009-2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]

Modes of infection

The HIV epidemic in Belgium mainly affects two populations: men who have sex with men (MSM), mainly of Belgian or other European nationality, and men and women who have contracted the virus through heterosexual relations (95% of the HIV-infected women and 32% of the men), mainly from sub-Saharan Africa.

Over the last 6 years, the main decrease in the number of new HIV diagnoses occurred in both concerned populations, whilst the decrease observed in other populations such as the Belgian heterosexuals is less clear, therefore taking up a proportionally larger share. The proportion of new infections in injecting drug users (PWID) remains very limited. Lastly, it is also important to note that there is a significant proportion of new infections for which the mode of transmission is unknown (28.8% in 2020).

Number of new HIV diagnoses by probable mode of infection, Belgium, 1999-2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]
Nationality by mode of infection

In 2020, 40% of the HIV cases diagnosed among MSM were of Belgian nationality. This proportion has strongly decreased in the last few years (72% in 2009, 61% in 2016 and 2017, and 50% in 2018). Among people infected by heterosexual contact, 44% were of sub-Saharan nationality in 2020. They were 60% in 2009 and 45% in 2018.

  • MSM
  • Heterosexuals

Number of new HIV diagnoses in MSM by nationality, Belgium, 1995-2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]

Number of new HIV diagnoses in heterosexuals by nationality, Belgium, 1995-2020
Source: Epidémiologie du SIDA et de l’infection à VIH en Belgique, Sciensano, 2021 [1]

Estimation of the HIV prevalence in Belgium

In 2020, Sciensano has estimated the number of people living with undiagnosed HIV [1] based on a tool developed by ECDC [2]. 1,585 people living with HIV in Belgium were not aware of their seropositivity.

Note: the prevalence estimated by the model is lower than the total number of people diagnosed with HIV since the beginning of the epidemic (31,695). This difference is mainly due to deaths and people who have left the territory. In addition, some duplication cannot be excluded due to the old personal identifier. Finally, it should be noted that these estimates have been calculated on the basis of available data, and that missing data may affect accuracy.

4. Other sexually transmitted infections

Situation in 2018

Belgium

Chlamydia is the most common STI in Belgium with 80 reported cases per 100,000 in 2018. Chlamydia infections are more frequent in women, with the highest notification rate among women aged 20-24.

Gonorrhea and syphilis are less common, with respectively 19 and 14 reported cases per 100,000 in 2018. Most gonorrhea and syphilis cases are registered among men, especially among men who have sex with men (MSM). The highest number of gonorrhea and syphilis cases are reported among men aged 25-29 and 30-39, respectively.

Trends

Between 2002 and 2018, the chlamydia notification rates increased from 9.5 cases/100,000 in 2002 to 80.2 cases/100,000 in 2018, while the notification rates of gonorrhea and syphilis increased to a lesser extent.

A similar increase is observed in the test intensity for chlamydia and for gonorrhea, (except in 2015 where the testing rate of gonorrhea evolved faster than the reported rate of the cases). These similar evolutions in both the testing rates and the reported infections suggest that the apparent rise in reported cases could be a consequence of an intensified testing rather than an increase in incidence. Indeed, for chlamydia infection, it is generally accepted that the actual incidence has remained stable over time. Also for gonorrhea, the incidence does not seem to have increased at the level of the general population. However, additional information provided by the STI clinical network suggests that unsafe sexual practices have become more common in certain population groups (especially MSM), leading to a focused increase in the incidence and reinfections with gonorrhea and syphilis in this group.

5. Read more

View the metadata for this indicator

Sciensano: HIV/AIDS surveillance

Sciensano: STI surveillance

Sciensano Epistat: Determinants of Sexually Transmitted Infections 

Definitions

HIV/AIDS
HIV infection and AIDS are the acronyms of "Human Immunodeficiency Virus" (HIV) infection and "Acquired Immune Deficiency Syndrome" (AIDS). Initial HIV infection is most often asymptomatic, while people may experience influenza-like symptoms. This is followed by a prolonged period with no symptoms. If the infection progresses, it interferes more with the immune system, increasing the risk of developing infections such as tuberculosis, as well as other opportunistic infections, and tumors which are rare in people who have normal immune function. These late symptoms of infection are referred to as AIDS. Since the late 1990s, efficient antiretroviral treatment exists that can slow down the progrression of the disease.

References

[1] Epidémiologie du SIDA et de l'infection à VIH en Belgique. Situation au 31 décembre 2020. Brussels: Sciensano; 2021. https://doi.org/10.25608/zepg-vg62

[2] European Centre for Disease Prevention and Control. HIV Modelling Tool. 2015. https://www.ecdc.europa.eu/en/publications-data/hiv-modelling-tool

[3] European Centre for Disease Prevention and Control/WHO Regional Office for Europe. HIV/AIDS surveillance in Europe 2021 – 2020 data. Stockholm: ECDC; 2021. https://www.ecdc.europa.eu/en/publications-data/hiv-aids-surveillance-europe-2021-2020-data

[4] Surveillance des infections sexuellement transmissibles. Données pour la période 2014-2016. Brussels: Sciensano; 2020. https://www.sciensano.be/sites/www.wiv-isp.be/files/surv_sti_1416_fr.pdf