Is Madagascar at risk of experiencing a widespread HIV epidemic?

17/01/2024

A study led by Catalan researchers aims to identify the main factors of vulnerability to HIV in the population of Madagascar, a country that has historically had low prevalence but has seen an increase in infections in recent years. The study seeks to analyze the reasons why the infection might transition from being restricted to specific vulnerable populations to becoming widespread.

In 1981, the first cases of AIDS were described in San Francisco (USA), and soon its infectious nature was determined, along with the isolation of its causative agent, HIV, and the identification of transmission mechanisms. At that time, the world became aware that the infection was already widespread in sub-Saharan Africa, where the majority of infections still occur today, specifically in southern Africa with a pattern of generalized epidemic. A generalized epidemic is one in which the majority of cases are detected in the general population with a prevalence above 2 or 3%. In contrast, a concentrated epidemic is one in which the majority of cases occur in well-identified at-risk populations, such as sex workers, men who have sex with men, or injectable drug users. Dr. David Alonso, a researcher at the Center for Advanced Studies in Blanes (CEAB-CSIC) and one of the researchers involved in the study, comments, “Determining the factors influencing the transition from a concentrated HIV epidemic to a generalized epidemic is essential for establishing prevention measures and preventing this generalization. It is also crucial to understand why some countries or regions in sub-Saharan Africa show different epidemic patterns.”

Dr. Xavier Vallès, a medical researcher at the Fight Infections Foundation, affiliated with PROSICS, the Catalan Institute of Health, and the Germans Trias i Pujol Research Institute (IGTP), along with Dr. David Alonso, a researcher at the Center for Advanced Studies in Blanes (CEAB-CSIC), explore in the study “A potential transition from a concentrated to a generalized HIV epidemic: the case of Madagascar“, published in the Infectious Diseases of Poverty journal, the vulnerability factors present in Madagascar. They analyze available epidemiological data and the specific cultural and geographic factors of the country.

Difference between a concentrated epidemic and a generalized one from a public health perspective

From a healthcare standpoint, the transition from a concentrated to a generalized epidemic represents a paradigm shift in the control and prevention of HIV and AIDS. In a concentrated epidemic, public health efforts can be targeted to contain it within well-defined vulnerable groups. If successful in controlling it within this population, the broader community is protected, and the epidemic may recede in the general population. In other words, the epidemic cannot survive if it is effectively managed in these population segments.

On the contrary, in the case of a generalized epidemic, persistence is expected despite focused actions on the most vulnerable groups. There is no longer a window of opportunity to contain it with significantly fewer resources and highly targeted interventions. Examples include promoting the use of sterile needles among injectable drug users or advocating for pre-exposure prophylaxis (PrEP) and condoms in other at-risk groups. Preventing this transition is, therefore, highly relevant.

Madagascar as a Case Study

This research employs Madagascar as a case study to determine the epidemiological transition of HIV. The island of Madagascar is located off the east coast of Africa, near Mozambique and South Africa, with a population of approximately 30 million people. In contrast to the situation in southern Africa, Madagascar, according to official data, exhibits a low prevalence of HIV in the general population (less than 1%), alongside a high prevalence of HIV among vulnerable populations on the island (above 10 or 15% in many cities). Therefore, it conforms to a model of a concentrated epidemic, which is surprising considering that in Madagascar, the most recognized risk factors associated with acquiring HIV are prevalent.

Widespread inconsistent and erratic condom use is common among the young population, along with a high prevalence of multiple sexual partnerships, the increasingly prevalent practice of transactional sex among young girls driven by poverty, and a very high incidence of Sexually Transmitted Infections (STIs). Since the 1990s, earlier studies had already predicted that Madagascar was approaching an epidemiological turning point, indicating a shift from a concentrated infection in the high-risk population to a generalized epidemic within a few years. However, this transition has not occurred as of today; why has this not happened?

This scenario is highly interesting for exploring the mechanisms of transition and, more importantly, finding answers to justify and implement appropriate control and prevention measures if this risk is confirmed.

In recent years, healthcare professionals across the country have been alerting to an increase in infections in the general population. This fact should raise concerns for health authorities.

So, why haven’t we witnessed a generalized epidemic like in neighboring countries yet? The study suggests that the late introduction of HIV to the island and the traditional practice of male circumcision, which protects against HIV transmission, may have slowed or delayed the spread of HIV in the country. However, the study also points out that considering the recent increase in infections and the interaction of risk factors associated with young women, along with the impact of acute HIV infections on epidemiological dynamics, neither the protective effect of circumcision nor the late introduction of the virus into the country are sufficient to contain the disease’s expansion in Madagascar. Therefore, it is considered a plausible scenario that the epidemic will become generalized in the coming years.

Work Methodology

This is a modeling study that has utilized all available epidemiological and demographic data in Madagascar, as well as an assessment through a thorough literature search of risk and protective factors present in the country. All this information has been parameterized with necessary and plausible assumptions based on the knowledge of HIV in other more studied contexts. This has allowed the creation of a mathematical model that replicates how all the evaluated factors interact (circumcision, dates of virus introduction in Madagascar, general population behavior, and specifically that of younger women, interaction between sex workers and the general population, HIV infection at different stages of the disease, etc.).

Conclusion: Madagascar may undergo a silent transition of the HIV epidemic

In conclusion, the study determines that at this moment, there is not enough empirical evidence to specify the current epidemiological situation of HIV in Madagascar due to the weakness of the epidemiological surveillance system. However, the results strongly suggest that Madagascar may be on the verge of a shift towards a high epidemic prevalence in the general population similar to that observed in neighboring countries such as South Africa or Mozambique within a few years. Such a generalization would have severe consequences in a country already impoverished with a fragile healthcare system. The study also highlights the gender vulnerability and poverty that underlie this potential generalization.

The most important conclusion is that, in the face of this scenario, action is needed on two levels: strengthening the response to HIV and implementing a more robust epidemiological surveillance system to better determine the real situation and act accordingly. The study also provides a comprehensive model that includes biological, behavioral, cultural, and even geographical factors, allowing for a better understanding of the epidemiological dynamics of HIV in other countries.

Dr. Xavier Vallès, a researcher at the Fight Infections Foundation and one of the leading investigators alongside Dr. David Alonso from the Center for Advanced Studies of Blanes (CEAB-CSIC), emphasizes that: “Our research highlights the need for more qualitative and quantitative data to understand the current dynamics of HIV/AIDS on the island of Madagascar. This lack of information should urge the leaders of the country’s public health and international agencies that fund and support HIV response in low- and middle-income countries to increase efforts to collect more data and improve infection diagnoses. Our research aims only to draw attention to a potential public health crisis and to lay the groundwork for appropriate responses and research initiatives. Action is necessary before the evidence confirms that it is already too late.”

This work is an example of how collaboration between disciplines and between institutions is often the key to obtaining novel results.