This work was initially designed to identify risk factors that may be associated with the HIV epidemic in Djibouti. The value of this research led to the establishment of an epidemiological surveillance system for HIV. But we cannot develop an alone surveillance system without addressing the epidemiological surveillance system in its entirety. Which system suffered from a lack of resources, low adherence of the healthcare system and lack of political will to make it a tool for decision support. In this context, we conducted our research and we received all the political and technical support to meet this challenge in a developing country. With support from WHO, we have implemented a sentinel surveillance system for HIV that does not rely only risk group or limited area but on the general population through annual anonymous surveys noncorrelated. Actually, we move to the second generation surveillance. We have also established an integrated surveillance system for vaccinepreventable diseases (diphtheria, pertussis, neonatal tetanus, Poliomyelitis, Measles, Meningitis, Mumps and Rubella) and epidemic-prone diseases such as Cholera, Malaria, avian flu and hemorrhagic fevers. The surveillance approach is primarily a clinical or syndromic secondarily confirmed by biology. Two objectives have been attended: 1. Risk factors for HIV in Djibouti: This study found specific risk factors to our context; Khat consumption by the unemployed and blood transfusion are specifically associated with HIV infection in Djibouti. 2. Dynamics of the epidemic of cholera in the Horn of Africa (HoA), this study is nourished by a rich field experience that led to the monitoring of stowaways migrants of the cholera epidemic in the HoA. We discovered the emergence of a new serotype unknown in previous waves of cholera outbreaks. 11 In addition, we are not limited ourself in the establishment of a disease surveillance system on human level. We had been interested on vectors level. At Djibouti, vector-borne diseases constitute a public health threat. Indeed, outside the malaria we had Dengue Fever, West Nile, Chikungunya and myiasis. The regional context of the Rift Valley Fever (RFV) was hardly reassuring. There was an urgent need to establish an entomological surveillance through human resources training and reinforcement of the entomological laboratory. This was possible through the support of NAMRU-3. Soon, we were able to mount the device and conduct monitoring, capturing, breeding and biological surveillance. Globally, we managed an epidemiological challenge and health monitoring in a context of limited resources with multiple priorities. We took the objective of our thesis and our international scientific collaborations to deploy a new epidemiological surveillance system, train the staff, and mobilize a significant investment in the development of the health information system. Soon, our system has detected outbreaks of cholera, measles and pertussis but also emerging diseases that were unknown (possibly just need research) in this region of the world: myiasis, avian influenza H5N1, West Nile virus among others. Thus our work is its consistency in the richness of the experiences we could share with other developing countries, in a North-South dialogue and respectful of the original need to increase capacity and local resources and transfer of technologies with international standards.