Recent and future developments in the epidemiology of the infectious diseases

Abstract

Microbiology, that is the unseen living world, is only known very superficially but our knowledge is growing rapidly. This is exemplified by metagenomic studies where all nucleic acids are sequenced from the environment, showing that 70% of sequences obtained from the environment have no match with any database (Eukaryotes, Bacteria, viruses or Archae) [1], This is measuring objectively our level of ignorance. Therefore understanding now completely human diseases is impossible because of this gap of knowledge of the potential infectious hazards of our environment. This gap of knowledge can result in overinterpretation of currently known factors, if our ignorance is not acknowledged. As a result, conclusions based on statistical tendencies inducted from our current knowledge, will be indeed challenged in the future. Recently new tools such as 16S rDNA amplification and sequencing has allowed the discovery and identification of hundreds of new bacterial pathogens in the 10 last years [2]. As a matter of fact the number of identified bacteria species was multiplied by 4.5. Many viruses were also identified [3]. Diseases caused by these agents could not have been understood before. There is a critical need to close this gap as soon as possible and to invest massively in identification of microorganisms from our body and our environment. The new discovered viruses and microbes will not only allow clarifying the etiology of diseases already considered as caused by microbes, but they will showed to be involved in diseases not currently considered infections such as cancer or obesity. The development of the epidemiology of infectious diseases will develop in my point of view in three major directions in the coming years. First we need to focus on the two most common causes of mortality in the world that are the diarrheal diseases and pneumonias that are both presumably of infectious origin. These pathologies are also the most neglected diseases [4]. These two big killers are prevalent both in developed and developing countries. The identification of causative agents in these diseases commonly fails, because of the lack of knowledge on etiologic agents and the lack of tools allowing to identify rapidly the causative agents in a point of care strategy [5]. The number of recognized microorganisms in these diseases is growing but is currently still insufficient to explain most cases. Among the major findings of the last years are the discovery of new respiratory viruses (Metapneumovirus, Coronavirus) [6, 7]. The prevalence of these viruses is significant and can explain many cases. The role of new viruses of diarrhoeas was also identified such as that of Norovirus [8, 9]. Finally the po sibility of using multiplexing diagnostic tests will make it possible to have a better epidemiologic knowledge of these infections [10]. However, the detection of multiple potential pathogens may complexify the understanding and the diagnostic of gastroenteritis or pneumonia. Moreover, it should be noted that the precise knowledge of the route of transmission routes for pneumonia and the diarrheal infections diseases is still very incomplete. This is exemplified by the current situation where preventive measures, that we are taking today, are unable to control the winter epidemics of gastroenteritis and pneumonias including in developed countries, such as in Europe. The current mortality and transmission of influenza is frightening despite available vaccine. Any new mutant with different immunogenicity and/or pathogenicity can determine a dramatic increase of winter mortality as we do not know how to D. Raoult (El) Unite des Rickettsies, Faculte de Medecine, URMITE CNRSIRD 6236, 13385 Marseille, France e-mail: didier.raoult@gmail.conn