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Highlights • SARS-CoV-2 Quantification. • Multiplex one-step reaction. • High-sensitivity and specificity assay., Introduction Coronavirus disease-2019 (COVID-19) is a disease caused by Severe Acute Respiratory Syndrome Virus 2 (SARS-CoV-2) that emerged in China in late 2019. The rapid viral spread has made the disease a public health emergency of worldwide concern. The gold standard for diagnosing SARS-CoV-2 is reverse transcription followed by qualitative real-time polymerase chain reaction (RT-qPCR); however, the role of viral load quantification has not been thoroughly investigated yet. Objective The aim of this study was to develop a high-precision quantitative one-step RT-qPCR reaction using the association of the viral target and the human target in the same reaction. Methods The assay standardization involved the absolute quantification method, with serial dilutions of a plasmid with the N gene in a biological matrix to build a standard curve. Results and Discussion The results demonstrated the possibility of quantifying as few as 2.5 copies/reaction and an analysis of 244 patients with known results selected by cross-section that revealed 100% agreement with a qualitative RT-qPCR assay registered by Anvisa. In this population, it was possible to quantify patients with between 2.59 and 3.5 × 107 copies per reaction and negative patients continued to indicate the same result. Conclusion This assay can be a useful tool for a proper patient management, because the level and duration of viral replication are important factors to assess the risk of transmission and to guide decisions regarding the isolation and release of patients; an accurate diagnosis is critical information, whereas the current COVID-19 pandemic represents the biggest current global health problem.

Introdução: Doenças respiratórias caracterizam-se como infecções que causam obstrução da passagem de ar tanto a nível do trato respiratório superior como inferior e estão entre as infecções de maior índice de morbimortalidade do mundo. Objetivos: O presente trabalho tem como objetivo analisar as principais infecções respiratórias de importância clínica e os principais agentes etiológicos, compilando os tipos de infecções, agentes etiológicos mais prevalentes e os principais locais de estudo. Materiais e Métodos: Trata-se de uma revisão sistemática realizada mediante pesquisa de artigos publicados entre os anos de 2010 e 2016, nos idiomas Português, Espanhol e Inglês. A coleta eletrônica foi conduzida utilizando os bancos de dados MEDLINE/PubMed e BVS e usando os seguintes descritores, respiratory tract infection, epidemiology, mortality e transmission, indexados no Medical Subject Headings database (MeSH). Resultados: Seguindo os critérios de inclusão e exclusão, foram selecionados 33 estudos para revisão. Foi perceptível o alto índice de publicações do Brasil referente ao tema, seguido da China, EUA, Áustria e Reino Unido. Foi observado que grande parte dos estudos mencionou a influenza como patologia clínica predominante, ficando evidente que o principal agente causador das infecções respiratórias foi o agente etiológico viral, seguido do bacteriano. Conclusão: Constatou-se uma alta distribuição geográfica dos estudos referente ao tema, destacando o Brasil como o país com o maior número de publicações. Porém, o assunto ainda é pouco discutido frente ao grande impacto socioeconômico causado pelo mesmo. No que diz respeito aos agentes etiológicos causadores das infecções respiratórias, prevaleceram os vírus, sugerindo então um melhor esquema de diagnóstico a cerca desse tipo de infecção. Introduction: Respiratory diseases are defined as infections that obstruct the air passage both at the upper and lower respiratory tract and are among the infections with the highest morbidity and mortality rate in the world. Objectives: This study aims to analyze the respiratory infections of clinical importance and their main etiological agents, compiling the types of infections, the most prevalent etiological agents, and the main study sites. Materials and Methods: This is a systematic review performed through articles published between 2010 and 2016 in Portuguese, Spanish, and English. The electronic collect was conducted using the MEDLINE / PubMed and BVS databases and using the following descriptors, respiratory tract infection, epidemiology, mortality, and transmission, indexed in Medical Subject Headings database (MeSH). Results: Following the inclusion and exclusion criteria, 33 studies were selected for review. It was noticeable the high index of publications of Brazil referring to the subject, followed by China, USA, Austria and United Kingdom. It was observed that most of the studies mentioned influenza as the predominant respiratory clinical pathology. It is evident that the main cause of the respiratory infections was the viral etiologic agent followed by bacteria. Conclusion: We found a high geographical distribution of the studies related to the topic, where Brazil was highlighted as the country in which there were more publications. However, the subject is still little discussed given the socioeconomic impact caused by it. Concerning the etiological agents that cause respiratory infections, viruses prevailed, suggesting a better diagnostic approach to this type of infection.