Infection with the Human Immunodeficiency Virus (HIV) weakens the human immune system [1] . This makes the immune system susceptible to all opportunistic diseases [2] . Worldwide, HIV remains a major public health burden, with around 40 million people expected to be HIV-positive in 2023 [3] . In Chad, the first case was reported in 1986 [4] , and the current prevalence is 1.3%. Current treatment for HIV infection is based on blocking the virus with a combination of a three-drug antiretroviral (ARV) therapy. There is no effective curative treatment, but vaccine trials are underway in some developed countries [5] .

According to the UNAIDS report reported by the World Health Organisation (WHO), the number of people infected worldwide since the appearance of HIV is estimated at more than 79.3 million, with 39.9 million people living with HIV, of whom more than 26 million live in Africa and 20.5 million in West and Central Africa [6] . More than 30.7 million people worldwide now have access to treatment [7] . Despite advances in treatment, the number of deaths linked to HIV/AIDS in 2023 is estimated at around 630,000, and the number of new infections is estimated at 3 million worldwide [7] . However, many infected people do not know their status, and most of them live in Africa.

Despite the tireless efforts of the authorities and partners, access to screening remains a major challenge. This makes HIV infection a major public health issue, with enormous challenges in terms of prevention, screening and comprehensive care.

In Chad, the prevalence of people living with HIV (PLHIV) is estimated at 1.3% among the general population aged 15 - 49 according to data from the EDST 2014-2015 study [4] . This prevalence is relatively low compared with other countries in the sub-region, which, according to the WHO, varies between 3% and 5%. However, the issue remains worrying, especially when there is a disparity in prevalence between provinces, as well as community circulation of the disease in the general population. Prevention strategies involving raising awareness, communication and education, collaboration between the public and private sectors, and community involvement in the fight against the disease are all needed to put an end to this epidemic.

This review provides an overview of the problem of HIV infection in Chad in recent years. The aim of this study is to provide information on the challenges of diagnosing, treating and preventing HIV infection in Chad.

On the basis of the inclusion criteria, 52 articles dealing with HIV-1 in Chad were found. The diagram used to select the articles is shown in Figure 1 below.

Of the 48 articles retrieved, 37 were selected (37/48, i.e. 77%) and full texts were obtained and nine (09) articles retrieved (9/48, i.e. 23%) were found cited in the bibliographic references of the articles, but the full texts were not found in the search engines. Fourteen (14) articles were excluded.

This review provides an understanding of the epidemiology of HIV disease, prevention methods, diagnosis and treatment.

The global HIV-1 trend in 2023 reported by UNAIDS shows a worldwide prevalence of 1.0% among adults aged 15 to 49, with 1.3% among women and 0.7% among adults aged 25 to 49 among men [3] . New infections are estimated at 1.3 million, and there are approximately 5.4 million people living with the disease who did not know they were living with HIV in 2023 (UNAIDS 2024). Around 44% (over 210,000) of new HIV infections in 2023 are reported among women, girls and adolescents aged 15 to 24. However, there has been a considerable decrease of 62% in new HIV infections among children. On average, more than 4,000 adolescent girls and young women aged between 15 and 24 contract HIV every week.

Given these prevalences, the goal of eliminating AIDS by 2030 will be far from realistic.

The number of adults and children living with HIV was estimated at 110,000, with over 81,000 living with the disease and unaware of their status. The number of people on ART is 69,000, with 4500 new infections and 3500 deaths per year.

In terms of prevention, the old strategies have been abandoned. Today, new prevention strategies are not well documented.

In terms of treatment, many people do not have access to adequate care. In practical terms, HIV care in health facilities has been virtually abandoned by the medical profession. In most health facilities, care is provided by psychosocial counsellors (CPS). However, in some parts of Chad, an HIV-positive patient could end his or her life without being seen or consulted by qualified medical staff. However, comprehensive HIV treatment is based on an approach that combines blocking the development of the virus through a triple combination of antiretroviral drugs, boosting the immune system and regular monitoring of viremia (viral load), as well as research into and prevention of other opportunistic pathologies. Such treatment is difficult and requires qualified staff.

Access to viral load, defined as the level of virions circulating in the blood of HIV-infected people, is very poor in Chad. It is used to monitor the progression of infection, to track patients’ compliance with treatment and to ensure the effectiveness of ARV treatment, defining the success or failure of ARV therapy.

Accessing a viral load test is a fundamental element of treatment, but the rate of access is very low in Chad. In 2020, according to official data, the rate of access to viral load for people on ART was estimated at 6.4% in Chad. This rate rose slightly in 2022 to around 19.2%. Despite these significant advances in terms of access to the viral load, the rate of suppression remains highly variable at around 82% [30] .

The reasons for this low figure are largely due to a lack of awareness of the benefits of viral load testing among prescribers and patients themselves.

It should be noted that viral load is used to measure the efficacy of ART in patients on ART [55] , and is also a key indicator for assessing the third UNAIDS performance indicator, according to which 95% of people on antiretroviral treatment should have a suppressed viral load [56] . This suppression is synonymous with non-transmission [57] and makes it possible to minimise virological failures by adapting treatment according to the levels of failure observed. According to previous studies, it varies between 14% and 53% after 6 to 24 months of initiation of treatment [58] [59] . This makes it possible to minimise new infections [60] and even eradicate the disease.

Very few studies have been carried out on the management of HIV disease in Chad. The few studies carried out in Chad focus mainly on drug toxicity, risk factors for other diseases and patient follow-up.

In addition, there is a virtual absence of studies on compliance and acceptability of treatment, and rarely on resistance.

Researchers in Chad need to develop research projects in this area in order to deepen research into these themes.

As for the introduction of the new dolutegravir-based therapy, since 2023 the transition has been effective and all patients have been switched to the dolutegravir-based regimen, even though a few alternatives molecules are still in circulation. By 2023, all patients on ART have been switched to the dolutegravir-based regimen, including patients in treatment failure. The Tenefovir/Lamuvidine/Dolutegravir (TLD) triple therapy regimen was selected as a first-line regimen.

A key issue that was not taken into account when dolutegravir was introduced was the phenomenon of HIV resistance to ARVs in adults and children.

The circulation of resistant strains of the human immunodeficiency virus (HIV) and the emergence of antiretroviral-resistant strains are likely possible [61] . In Chad, most treatment centres are faced with unavailability and frequent drug stock-outs. Interruptions in ARV treatment have been reported to be a source of therapeutic failure and a major factor in the proliferation of HIV drug resistance [62] [63] .

There are very few studies on HIV resistance to ARVs and no studies on HIV-1 resistance in children and pregnant women.

Essentially, it is important to take the issue of HIV resistance in pregnant women very seriously by developing the programme for monitoring and following up HIV-positive mothers who have failed virological tests. Awareness and referral strategies also need to be developed to address concerns.

The availability of ARVs varies from one part of the country to another. In some provinces, all the drug options needed to treat HIV are available. In other parts of the country, however, there are occasional or total shortages. However, very little data is available on the availability of ARVs, despite the fact that the government and its technical and financial partners, in particular the Global Fund (GF), have deployed enormous resources to purchase ARVs.

It is important to point out that no strategy or approach to HIV vaccination is yet envisaged in Chad.

In Chad, the fight against HIV infection remains a major challenge and a health problem because of the difficulties involved in diagnosing and treating PLHIV, despite the efforts made by the government and its financial partners.

The results of this study show that there is heterogeneity in HIV prevalence and very little data on the different themes addressed and analysed in this study. It is important that lines of research based on the issues addressed can be developed in order to devise control strategies that reflect the reality of the country.

The limitations of this study lie in the availability of published articles and the heterogeneity of the methodologies used, which meant that it was not possible to carry out a meta-analysis to summarise the results statistically.

All authors have read and approved the final manuscript.

Special thanks to Natasha Turyasingura of the Department of Epidemiology of Microbial Diseases, Laboratory of Epidemiology in Public Health, Yale School of Public Health (USA).