Editorial: SARS-CoV-2: virology, epidemiology, diagnosis, pathogenesis and control, volume II

SARS-CoV-2 was first described in late December 2019 and rapidly established sustained human-to-human transmission, causing the coronavirus disease 2019 (COVID-19) 1,2 . To date, more than 779 million cases have been documented worldwide, and COVID-19 has had a tremendous impact on global public health, representing one of the greatest crises in human history 3,4 . Remarkably, the rapid response to SARS-CoV-2 brought together the scientific community, biotech companies, and public health authorities to develop effective vaccines, diagnostic tools, new therapies, and coordinated public health measures to control the virus's spread 5 .Yet despite extensive efforts since its emergence to advance knowledge and address key gaps, several important aspects of the virus and the disease it causes remain incompletely understood. To further expand knowledge of SARS-CoV-2 and COVID-19, we launched Volume II of the Research Topic "SARS-CoV-2: Virology, Epidemiology, Diagnosis, Pathogenesis, and Control," building on the success of the first volume (Volume I). In this Editorial Article, we summarize the main findings of the studies published in this Research Topic.The COVID-19 pandemic was characterized by multiple waves of infection, reflecting the dynamic interplay between viral evolution and population immunity 6,7 . To address the impact of population mobility on SARS-CoV-2 transmission and healthcare system burden, Guo et al. developed a modeling framework using real SARS-CoV-2 data to assess how inter-regional population mobility influences epidemic spread and healthcare system burden. Using two cities, Taiyuan-Jinzhong and Linfen-Yuncheng, in China as research subjects, the study shows that mobility patterns critically influence transmission dynamics and healthcare congestion, emphasizing the need for coordinated, region-specific intervention strategies. Since its discovery, SARS-CoV-2 has been characterized by the emergence of variants with distinct mutational profiles 8,9 . Within this context, Bruno et al. examined SARS-CoV-2 genomic surveillance across four Andean countries using 16,867 sequences collected between 2020 and 2024. In that study, the authors showed the temporal progression of major lineages, from early variants (19A/19B) to Gamma, Delta, Lambda, Mu, and later the dominance of Omicron and its sub-lineages, including JN.1.Computational analysis revealed a consistent pattern of viral evolution across countries, emphasizing rapid transnational spread within the region. These findings emphasize the importance of coordinated regional genomic surveillance to track viral evolution and enhance readiness for public health responses 10 .Wastewater-based surveillance has become a critical approach for tracking community-level SARS-CoV-2 transmission in a timely and non-invasive manner and has been extensively investigated since the beginning of the COVID-19 pandemic 11,12 . In this Understanding the clinical features and factors influencing disease severity is crucial for improving patient management and outcomes in COVID-19 13,14 . Chen et al. The immune response to SARS-CoV-2 infection and its differences across populations remain key to understanding COVID-19 outcomes 7 . Through these lines, Dassaye et al. assessed SARS-CoV-2 seroprevalence among 645 participants, including schoolchildren, parents, and teachers in a semi-rural setting in South Africa. They found high levels of seropositivity across all groups, despite a low proportion of self-reported prior infections. These findings suggest widespread exposure to SARS-CoV-2, likely driven by repeated waves of infection and a high prevalence of asymptomatic cases.Building on population-level evidence of widespread exposure, Lizarazo-Taborda The rapid deployment of COVID-19 vaccines has led to a significant decrease in worldwide deaths, saving millions of lives during the first year of implementation 15 . However, while vaccines are among the most effective strategies for reducing the burden of infectious diseases, vaccine hesitancy was considered a significant challenge throughout the COVID-19 pandemic 16 . To address this question, Sardinha et al. conducted a systematic review and meta-analysis to estimate COVID-19 vaccine hesitancy in Brazil, reporting an overall prevalence of 13.3%. Hesitancy was higher among parents of children and adolescents and was influenced by factors like misinformation, lack of knowledge, and sociodemographic features.Expanding on these findings, Luo et al. examined how access and trust influence vaccine uptake in a U.S. population. In an analysis of 255 individuals, they found that proximity to vaccination sites significantly increased vaccination rates, while greater distance reduced uptake. As shown in these and other studies, vaccine hesitancy continues to be a significant challenge that needs to be tackled urgently. Clearly, there is no single solution to this societal challenge, but it will require commitment and coordinated efforts from scientists, global health authorities, and society to enhance trust in vaccines and science.Data science and risk assessment are critical for navigating both the epidemiological and information landscapes of the COVID-19 pandemic 17 . In this context, Michalak et al. examined how COVID-19 risk is estimated across 101 countries, highlighting limitations in current approaches that underutilize testing data as a quantitative input. In that study, the authors demonstrated that probabilistic metrics, such as local infection probability, more effectively captured spatial transmission patterns than traditional indicators, highlighting the importance of incorporating testing data into risk assessment frameworks to enhance the accuracy of epidemic monitoring.The COVID-19 pandemic emerged with an unprecedented impact on global public health. Much has been done, and much has been learned from the efforts undertaken in recent years. The pandemic highlighted the resilience of the global community, particularly scientists, health professionals, and public health authorities, as well as many others who confronted this threat head-on. Importantly, much was achieved despite limited resources, especially in low-and middle-income countries (LMICs) 18 .Although the pandemic has mostly been controlled and SARS-CoV-2 continues to circulate globally, with cases emerging over time, these efforts must not stop. Continued vigilance and sustained monitoring remain essential. Equally important, the knowledge gained during the COVID-19 pandemic will be invaluable for addressing future public health crises of similar magnitude.