[en] Pneumonia is one of the major public health problems threats to child survival in large parts of the world. The burden of this disease in terms of morbidity and mortality remains unacceptably high with almost one million children dying every year as a result of pneumonia episode. Over 90% of these pneumonia-associated deaths in young children occur in developing countries and are mainly secondary to bacterial infections. The availability of effective vaccines against bacterial pneumonia, coupled with adequate and efficacious antibiotic treatments, should be sufficient to reduce this burden. In Morocco, a middle income country of North Africa, Pneumonia is the first cause of death of children under five of age. However, few data is available regarding its etiology and epidemiology. The first article of this thesis attempts to comprehensively review what was the available knowledge regarding pediatric pneumonia in Morocco, prior to the initiation of this project. Indeed, scarcity of data often hinders the implementation of measures to prevent and better manage these infections. This review confirms the alarming lack of recent data regarding pediatric pneumonia one of the major killers of children in Morocco. The second article of this thesis is a general overview on the epidemiology, etiology and the clinical presentation of acute respiratory infections in Moroccan children under the age of five years. Through our study, we were able to show a high prevalence of viral infections, with wheezing as the major clinical symptomatology. These findings are similar to what can be found in wealthy countries and markedly differ from the high bacterial burden that can be found in poorer settings, although overall case fatality rates remained unacceptably high in our setting. As a result of afore mentioned high case fatality rates in our series, we decided to investigate the specific risk factors upon admission for a bad prognosis during hospitalization. The results of this analysis are presented in the third article of this thesis. The article concluded that the early identification of factors associated with a poor prognosis could improve management strategies and the survival likelihood of Moroccan children with severe pneumonia. In the fourth article of this thesis, we chose to focus on two highly prevalent and potentially hazardous viruses causing acute respiratory infections in our setting, namely respiratory syncytial virus (RSV) and Human metapneumovirus (hMPV). In this analysis, we compared the epidemiological, clinical and laboratory features of these two infections, and concluded that despite the clinical presentation of those two pathogens was almost indistinguishable, hMPV tented to be highly more severe and significantly associated to a poor outcome. An early recognition of these viruses and good management of the cases is important to guarantee a better outcome. The fifth article of this thesis specifically addresses the use of antibiotics to treat acute respiratory infections in Morocco. By analyzing data on pre-admission antibiotics use, and intra-hospital antibiotics utilization, we discuss whether such valuable drugs are used rationally in the country. This analysis also reflects on whether antibiotic usage may have had or not an impact on antimicrobial resistance rates. The last article of this thesis examines data on the distribution of serotypes among streptococcus pneumoniae isolates from the nasopharynx of healthy children and compares it to those isolated among admitted children with clinical severe pneumonia. These data will be used as a baseline to help assessing the impact of the pneumococcal vaccine and to monitor any potential serotype replacement phenomena. Altogether, this thesis tries to offer a comprehensive snapshot of the situation of pediatric pneumonia in Morocco.

[es] A pesar de los esfuerzos hechos para reducir la carga de mortalidad causada por las infecciones respiratorias agudas, estas enfermedades se mantienen como uno de los principales peligros para la salud infantil en amplias zonas del mundo. Las medidas de control existentes son claramente insuficientes a la hora de reducir globalmente el impacto de infecciones tan comunes en la infancia. De hecho, la carga de estas enfermedades en términos de morbilidad y mortalidad persiste inaceptablemente alta con, anualmente, cerca de un millón de muertes anuales, lo que es lo mismo, una muerte cada 34 segundos. Las infecciones respiratorias agudas, siendo la neumonía su forma más paradigmática, son responsables del 15% de las muertes de niños menores de 5 años en el mundo. Más del 90% de estas infecciones respiratorias agudas se producen en los países en vías de desarrollo, fundamentalmente asociadas a neumonías bacterianas. Mientras que la enfermedad clínica puede afectar a cualquier grupo de edad, la mortalidad por neumonía se ve esencialmente circunscrita a los niños menores de cinco años en los países pobres. La disponibilidad de vacunas efectivas contra las neumonías bacterianas, sumada al uso adecuado de los tratamientos antibióticos, debería ser suficiente para reducir esta carga. Sin embargo, la identificación y tratamiento precoz de los episodios clínicos y al acceso a los centros de salud parecen constituirse como barreras infranqueables en la mayoría de los países pobres. Adicionalmente, la malnutrición y el bajo nivel socio económico imperante en muchos de estos entornos dónde las neumonías son un mayor problema, contribuyen desfavorablemente al mal pronóstico de estas infecciones. El conocimiento de los determinantes locales específicos de la enfermedad respiratoria aguda pediátrica en esos entornos ayudaría a entender o mejor por qué todavía estamos muy lejos de controlar adecuadamente estas infecciones, y profundizar sobre las razones por las cuales siguen causando un impacto tan importante en la salud del niño.