COVID-19 Resources

MDPI Comment on the COVID-19 Virus

Since 1996, MDPI has been committed to supporting the research community by providing the latest research freely available and making relevant and useful research available as quickly as possible. The world is current experiencing a pandemic of COVID-19, and researchers are working extremely hard to understand it and find a cure.

The values MDPI holds strongly are particularly important at the moment, and we will continue to publish relevant, peer-reviewed research as quickly as possible in open access format. This means that it will immediately be available for researchers, health professionals, and the general public to read, distribute, and reuse. We believe that scientific advancements will be crucial to overcoming this pandemic, and will do everything we can to support researchers working looking for solutions.

This page contains a variety of information related to COVID-19 available from MDPI, including journal articles, special issues, and preprints, among others.

29 pages, 992 KB

Open AccessArticle

Comparative Evaluation of Event-Based Forecasting Models for Thai Airport Passenger Traffic

by Thanrada Chaikajonwat and Autcha Araveeporn

Modelling 2026, 7(1), 26; https://doi.org/10.3390/modelling7010026 - 20 Jan 2026

Abstract

Accurate passenger traffic forecasting is vital for strategic planning in Thailand’s aviation industry. This study forecasts the monthly total number of passengers at Suvarnabhumi (BKK), Don Mueang (DMK), Chiang Mai (CNX), and Phuket (HKT) airports using data from 2017 to 2024. The dataset was partitioned into training (January 2017–December 2023) and testing (January–December 2024) sets. Six methods were compared: Single Exponential Smoothing, Holt’s, Holt’s with Events Adjustment, Holt–Winters Multiplicative, TBATS model, and Box–Jenkins. Performance was evaluated using Mean Absolute Percentage Error (MAPE) and Mean Absolute Error (MAE). The results indicate that the optimal forecasting method varies by airport characteristics. Holt’s Method with Events Adjustment, which incorporates major disruptions such as the COVID-19 pandemic, produced the most accurate forecasts for BKK and DMK by effectively capturing external shocks. In contrast, the Holt–Winters Multiplicative method performed best for CNX and HKT, reflecting strong seasonal patterns typically driven by tourism activities in these destinations. Full article

17 pages, 1546 KB

Open AccessArticle

Immune Imprinting Identified in Phage-Display Antibody Libraries Derived from Early Wild-Type and Late Omicron COVID-19 Convalescents

by Boyang Li, Mengxuan Wang, Fang Huang, Wei Wu, Jiaxin Fan, Lu Yang, Yongbing Pan, Mifang Liang and Kai Duan

Viruses 2026, 18(1), 132; https://doi.org/10.3390/v18010132 - 20 Jan 2026

Abstract

The rapid evolution of SARS-CoV-2, particularly the emergence of Omicron subvariants, has significantly reduced the efficacy of existing vaccines and monoclonal antibodies. This study investigates the phenomenon of immune imprinting by comparing two phage display antibody libraries derived from early 2020 wild-type SARS-CoV-2 convalescents (WT-AbLib) and early 2023 Omicron convalescents (Omi-AbLib). The capacity and diversity of both antibody libraries were systematically evaluated. The libraries were screened using BF.7 and XBB.1.5 antigens. WT-AbLib showed markedly reduced diversity after Omicron antigen selection, with dominant clones shifting from IGHV3-66-class broadly neutralizing antibodies (bnAbs) targeting the receptor-binding motif to IGHV1-46-class broadly non-neutralizing antibodies targeting conserved lateral receptor-binding domain (RBD) sites. Omi-AbLib maintained higher diversity, but dominant antibodies were also non-neutralizing and targeted the same conserved lateral region. These findings suggest that immune imprinting drives the dominance of broadly non-neutralizing antibodies following Omicron breakthrough or reinfection. This phenomenon provides a mechanistic explanation for persistent viral evasion and recurrent infection, and highlights major challenges for the development of next-generation broadly neutralizing therapeutics. Full article

(This article belongs to the Special Issue SARS-CoV-2 Neutralizing Antibodies, 3rd Edition)

16 pages, 1517 KB

Open AccessArticle

Digital Dating and the Syphilis Surge in Japan: Unraveling the Link Between Technology and STI Trends

by Yanru Jiang and Yiu-Wing Kam

Venereology 2026, 5(1), 5; https://doi.org/10.3390/venereology5010005 - 20 Jan 2026

Abstract

Background/Objectives: This study investigates the potential association between the sharp increase in syphilis cases in Japan and the growing popularity of dating apps, with a specific focus on the dynamics during the COVID-19 pandemic. Syphilis, a sexually transmitted infection (STIs) caused by Treponema pallidum, presents a significant global public health challenge despite being curable with antibiotics. In Japan, the incidence of syphilis has risen dramatically since 2013, surpassing 10,000 reported cases annually by 2022. Methods: To examine this trend, we analyzed the quarterly reported syphilis cases alongside active user data from three major dating apps (App1, App2, and App3) and conducted a stratified linear correlation analysis by gender and age group. Results: The results reveal that syphilis cases showed accelerated growth starting in the first quarter of 2021, and App 3 demonstrated the strongest positive correlation with new syphilis cases. The association was particularly significant among males aged 20–29 (R² = 0.70, p = 0.0007) and 30–39 (R² = 0.82, p < 0.0001). Conclusions: These findings suggest that the widespread use of dating apps may contribute to the rise in sexually transmitted infections, including syphilis, by facilitating extensive new sexual contacts. Notably, this trend became increasingly evident during the COVID-19 pandemic. Future STI prevention strategies should consider integrating dating apps as a potential medium for public health interventions. Additionally, strengthening sexual health services is essential to ensure that responses to global crises do not inadvertently undermine STI prevention and control efforts. Full article

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32 pages, 2119 KB

Open AccessArticle

Longitudinal Mobility and Temporal Use Patterns in Urban Parks: Multi-Year Evidence from the City of Las Vegas, 2018–2022

by Shuqi Hu, Zheng Zhu and Pai Liu

Sustainability 2026, 18(2), 1060; https://doi.org/10.3390/su18021060 - 20 Jan 2026

Abstract

Urban parks are central to public health and equity, yet less is known about how park travel distance, park “attractor” types, and time-of-day visitation rhythms co-evolved through and after the COVID-19 pandemic. Using anonymized smartphone mobility traces for public parks in Las Vegas, USA (2018–2022), we construct weekly origin–destination flows between census block groups (CBGs) and parks and link origins to socio-economic indicators. We first estimate visitor-weighted mean travel distance with a segmented time-series model that allows pandemic-related breakpoints. Results show that average park-trip distance (≈8.4 km pre-pandemic), including a substantial share of long-distance trips (≈52% of visits), contracted sharply at the onset of COVID-19, and that both travel radii and seasonal excursion peaks only partially rebounded by 2022. Next, cross-sectional OLS/WLS models (R² ≈ 0.08–0.14) indicate persistent socio-spatial disparities: CBGs with higher educational attainment and larger shares of Black and Hispanic residents are consistently associated with shorter park-trip distances, suggesting constrained recreational mobility for socially disadvantaged groups. We then identify a stable two-type park typology—local versus regional attractors—using clustering on origin diversity and long-distance share (silhouette ≈ 0.46–0.52); this typology is strongly related to visitation volume and temporal usage profiles. Finally, mixed-effects models of evening and late-night visit shares show that regional attractors sustain higher nighttime activity than local parks, even as citywide evening/late-night visitation dipped during the mid-pandemic period and only partly recovered thereafter. Overall, our findings reveal a durable post-pandemic re-scaling of park use toward more proximate, CBG-embedded patterns layered on enduring inequities in access to distant, destination-oriented parks. These insights offer actionable evidence for equitable park planning, targeted investment in high-need areas, and time-sensitive management strategies that account for daytime versus nighttime use. Full article

(This article belongs to the Special Issue Sustainable Urban Designs to Enhance Human Health and Well-Being)

16 pages, 1210 KB

Open AccessReview

The Renin Angiotensin System: Insights into the Role of ACE2 in Glomerular Injury Including SARS-CoV-2 Infection

by Everton Smith and James Scholey

Int. J. Mol. Sci. 2026, 27(2), 1033; https://doi.org/10.3390/ijms27021033 - 20 Jan 2026

Abstract

The circulating renin–angiotensin–aldosterone system (RAAS) plays a key role in regulating blood volume and electrolyte levels. While important for the maintenance of intravascular volume systemically, the local activation of tissue RAAS and the generation of angiotensin II contribute to inflammation and fibrosis. In the kidney, angiotensin II plays a key role in the development and progression of glomerular injury. Angiotensin-converting enzyme 2 (ACE2), an enzyme that degrades angiotensin II, is expressed in the glomerulus, focusing attention not only on the complexity of the RAAS but also identifying a potential new determinant of glomerular injury. Accordingly, we performed a narrative review using the search terms ACE2 and glomerulus in PubMed and Google Scholar to summarize the current understanding of the role of ACE2 in glomerular injury. We also discuss the role of ACE2 as a cellular receptor for SARS-CoV-2 and the potential impact of this function on glomerular injury in the setting of COVID-19. Full article

(This article belongs to the Section Molecular Biology)

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33 pages, 11240 KB

Open AccessArticle

Spatiotemporal Evolution and Maintenance Mechanisms of Urban Vitality in Mountainous Cities Using Multiscale Geographically and Temporally Weighted Regression

by Man Shu, Honggang Tang and Sicheng Wang

Sustainability 2026, 18(2), 1059; https://doi.org/10.3390/su18021059 - 20 Jan 2026

Abstract

Investigating the characteristics and influencing mechanisms of urban vitality in mountainous cities can contribute to enhanced urban resilience, optimised resource allocation, and sustainable development. However, most existing studies have focused on static analyses at single spatial scales, making it difficult to fully reveal the evolutionary trends of urban vitality under complex topographic constraints or the spatiotemporal heterogeneity of its influencing factors. This study examines Guiyang, one of China’s fastest-growing cities, focusing on both its economic development and population growth. Based on social media data and geospatial big data from 2019 to 2024, the spatiotemporal permutation scan statistics (STPSS) model was employed to identify spatiotemporal areas of interest (ST-AOIs) and to analyse the spatial distribution and day-night dynamics of urban vitality across different phases. Furthermore, by incorporating transportation and topographic factors characteristic of mountainous cities, the multiscale geographically and temporally weighted regression (MGTWR) model was applied to reveal the driving mechanisms of urban vitality. The main findings are as follows: (1) Urban vitality exhibits a multi-center, clustered structure, gradually expanding from gentle to steeper slopes over time, with activity patterns shifting from an afternoon peak to an all-day distribution. (2) Significant differences in regional vitality resilience were observed: the core vitality areas exhibited stable ST-AOI spatial patterns, flexible temporal rhythms, and strong adaptability; the emerging vitality areas recovered quickly with low losses, while low-vitality areas showed slow recovery and insufficient resilience. (3) The density of commercial service facilities and the level of housing prices were continuously enhancing factors for vitality improvement, whereas the density of subway stations and the degree of functional mix played key roles in supporting resilience during the COVID-19 pandemic. (4) The synergistic effect between transportation systems and commercial facilities is crucial for forming high-vitality zones in mountainous cities. In contrast, reliance on a single factor tends to lead to vitality spillover. This study provides a crucial foundation for promoting sustainable urban development in Guiyang and other mountainous regions. Full article

(This article belongs to the Special Issue Sustainable Transport and Land Use for a Sustainable Future)

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State-of-the-Art Webinars on COVID-19

WEBINAR 1: How to Avoid a New Lockdown?

The first webinar in the series, held on 17 April 2020, saw both Prof. Dr. Antoine Flahault, Director of the Institute of Global Health, University of Geneva, Switzerland, and Prof. Dr. Evelyne Bischof, Associate Professor, Shanghai University of Medicine and Health Sciences, Shanghai, China and Research physician, University Hospital of Basel, Basel, Switzerland speak on this topic.