Pathology of infectious diseases: new agents, opportunistic, neglectable, emergent, reemergent diseases and why not super resistant nosocomial bacteria?

Duarte-Neto, Amaro Nunes

The history of the pathology of infectious diseases coincides with the history of general pathology and modern medicine itself. From the earliest descriptions of the pathology of tuberculosis and yellow fever to the discovery of AIDS [13] [14] [15] ; the Ebola epidemic in the 1990s 16 ; the Bacillus anthracis bioterrorism attack in the early 2000s 17 ; the epidemics of SARS and pandemic influenza throughout the 2000s 18, 19 ; and more recently the Zika epidemic, [3] [4] [5] with congenital syndrome, the pathology of infectious diseases plays a decisive role in understanding the pathogenesis of an infectious agent. Moreover, the pathology of infectious diseases is part of preparedness in case of an epidemic, as it defines or excludes the diagnosis of a disease. With this medical and social function, the pathology of infectious diseases can reach the fullness of its importance with the autopsy, when the pathologist examines all organs of a fatal case, allowing him/her to determine the mechanism of transmission, the mechanism of injury through the involvement of all organ systems, and to determine the cause of death. Of equal importance, the pathologist can characterize the individual's in situ immune response, and predict the prognosis of an infectious disease and the therapeutic response by analyzing tissue damage. [20] [21] [22] The arsenal of methodologies used by the pathologist for diagnosing infectious disease is mostly based on classic, low-cost techniques that require familiarity and expertise with the morphological aspect of the agents to complete their report: hematoxylin and eosin, and special stains such as Grocott, Ziehl-Neelsen, period acid-Schiff, Mucicarmine, Giemsa, and others. 23 Added to them is indispensable electron microscopy (EM). Perhaps it is in the field of infectious diseases where the great importance of EM still lies, and it is worth maintaining the technique and art of this old ancillary method. EM can elucidate difficult cases by discovering the etiology of a disease (especially viruses), in glutaraldehyde-fixed or paraffin-embedded tissues during epidemics, where immunohistochemistry antibodies or polymerase chain reaction (PCR) primers are not yet available. 24 Molecular biology techniques such as in situ hybridization, PCR and gene sequencing-including next generation sequencingare new methods that can be used with frozen or fixed tissues; however, these techniques are not always available in resource-poor regions (Figure 2 ). 25 The expert in infectious disease pathology can act beyond the autopsy and analysis of surgical specimens (biopsies, cytology). The pathologist can assist research groups in evaluating the pathology of experimental models of infectious diseases and, within the new concept of "one health," interact with veterinarians, environmentalists, and epidemiologists in epidemic situations or in comparative pathology studies of zoonoses (e.g., leptospirosis, yellow fever, spotty fever, west Nile, etc.). 26 Considering all that has been commented on previously regarding the importance of the pathology of tropical infectious diseases, a recent review article, written by Hofman et al., 25 points out that this specialty needs to grow all over the world, stimulating the formation of young pathologists with expertise in this field. To reach this aim, stimulus must be created to attract resources to include new diagnostic methodologies in the field and to establish research, education, and patient-c