The COVID-19 outbreak has caused over three million deaths worldwide. Understanding the pathology of the disease and the factors that drive severe and fatal clinical outcomes is of special relevance. Studying the role of the respiratory microbiota in COVID-19 is especially important as the respiratory microbiota is known to interact with the host immune system, contributing to clinical outcomes in chronic and acute respiratory diseases. Here, we characterized the microbiota in the respiratory tract of patients with mild, severe, or fatal COVID-19, and compared it to healthy controls and patients with non-COVID-19-pneumonia. We comparatively studied the microbial composition, diversity, and microbiota structure between the study groups and correlated the results with clinical data. We found differences in the microbial composition for COVID-19 patients, healthy controls, and non-COVID-19 pneumonia controls. In particular, we detected a high number of potentially opportunistic pathogens associated with severe and fatal levels of the disease. Also, we found higher levels of dysbiosis in the respiratory microbiota of patients with COVID-19 compared to the healthy controls. In addition, we detected differences in diversity structure between the microbiota of patients with mild, severe, and fatal COVID-19, as well as the presence of specific bacteria that correlated with clinical variables associated with increased risk of mortality. In summary, our results demonstrate that increased dysbiosis of the respiratory tract microbiota in patients with COVID-19 along with a continuous loss of microbial complexity structure found in mild to fatal COVID-19 cases may potentially alter clinical outcomes in patients. Taken together, our findings identify the respiratory microbiota as a factor potentially associated with the severity of COVID-19.

During the first year of the SARS-CoV-2 pandemic in Mexico, more than two million people were infected. In this study, we analyzed full genome sequences from 27 February 2020 to 28 February 2021 to characterize the geographical and temporal distribution of SARS-CoV-2 lineages and identify the most common circulating lineages during this period. We defined six different geographical regions with particular dynamics of lineage circulation. The Northeast and Northwest regions were the ones that exhibited the highest lineage diversity, while the Central south and South/Southeast regions presented less diversity with predominance of a certain lineage. Additionally, by late February 2021, lineage B.1.1.519 represented more than 89% of all circulating lineages in the country.

Acute asthma exacerbations and pneumonia are important causes of morbidity and mortality in children and may coexist in the same children, although symptom overlap may lead to difficulties in diagnosis. Microbial and viral diversity and differential abundance of either may play an important role in infection susceptibility and the development of acute and chronic respiratory diseases. To describe the virome and bacteriome present in the upper respiratory tract of hospitalized children with a clinical diagnosis of asthma and pneumonia during an acute exacerbation and an acute respiratory illness ARI episode respectively. During the winter seasons of 2013–2014 and 2014–2015, 134 nasopharyngeal swabs samples of children <15 years of age with ARI hospitalized at a referral hospital for respiratory diseases were selected based on clinical diagnosis of asthma or pneumonia. The virome and bacteriome were characterized using Whole Genome Sequencing (WGS) and in-house bioinformatics analysis pipeline. The Asthma group was represented mainly by RV-C, BoV-1 and RSV-B and the pneumonia group by Bacteriophage EJ-1 and TTMV. TTV was found in both groups with a similar amount of reads. About bacterial composition Moraxella catarrhalis, Propionibacterium acnes and Acinetobacter were present in asthma and Veillonella parvula and Mycoplasma pneumoniae in pneumonia. Streptococcus pneumoniae and Haemophilus influenzae were mostly found with both asthma and pneumonia. Our results show a complex viral and bacterial composition in asthma and pneumonia groups with a strong association of RV-C presence in asthmatic children. We observed Streptococcus pneumoniae and Haemophilus influenzae concurrently in both groups.

In this study, we analyzed the sequences of SARS-CoV-2 isolates of the Delta variant in Mexico, which has completely replaced other previously circulating variants in the country due to its transmission advantage. Among all the Delta sublineages that were detected, 81.5 % were classified as AY.20, AY.26, and AY.100. According to publicly available data, these only reached a world prevalence of less than 1%, suggesting a possible Mexican origin. The signature mutations of these sublineages are described herein, and phylogenetic analyses and haplotype networks are used to track their spread across the country. Other frequently detected sublineages include AY.3, AY.62, AY.103, and AY.113. Over time, the main sublineages showed different geographical distributions, with AY.20 predominant in Central Mexico, AY.26 in the North, and AY.100 in the Northwest and South/Southeast. This work describes the circulation, from May to November 2021, of the primary sublineages of the Delta variant associated with the third wave of the COVID-19 pandemic in Mexico and highlights the importance of SARS-CoV-2 genomic surveillance for the timely identification of emerging variants that may impact public health.

Background: Viral infections play a significant role in causing acute respiratory infections (ARIs) and exacerbations of chronic diseases. Acute respiratory infections are now the leading cause of mortality in children worldwide, especially in developing countries. Recently, human rhinovirus (HRV) infection has been emerged as an important cause of pneumonia and asthma exacerbation.Objectives: To determine the role of several viral agents principally, respiratory syncytial virus, and HRV in children with ARIs and their relationship with asthma exacerbation and pneumonia.Methods: Between October 2011 and March 2014, 432 nasopharyngeal samples of children <15 years of age with ARI hospitalized at a referral hospital for respiratory diseases were tested for the presence of respiratory viruses using a multiplex RT‐qPCR. Clinical, epidemiological, and demographic data were collected and associated with symptomatology and viral infections.Results: Viral infections were detected in at least 59·7% of the enrolled patients, with HRV (26·6%) being the most frequently detected. HRV infections were associated with clinical features of asthma and difficulty in breathing such as wheezing (P = 0·0003), supraesternal (P = 0·046), and xiphoid retraction (P = 0·030). HRV subtype C (HRV‐C) infections were associated with asthma (P = 0·02).Conclusions: Human rhinovirus was the virus most commonly detected in pediatric patients with ARI. There is also an association of HRV‐C infection with asthma exacerbation, emphasizing the relevance of this virus in severe pediatric respiratory disease.