viruses Editorial Special Issue “Viral Shedding and Transmission in Zoonotic Diseases” Kateri Bertran 1,2, *, Martí Cortey 3, * and Miriã F. Criado 4, *,† 1 Unitat mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Spain 2 IRTA, Programa de Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Spain 3 Department of Animal Health and Anatomy, Faculty of Veterinary Sciences, Authonomous University of Barcelona, 08193 Barcelona, Spain 4 Center for Vaccines and Immunology, University of Georgia, Athens, GA 30602, USA * Correspondence: kateri.bertran@irta.cat (K.B.); marti.cortey@uab.cat (M.C.); mfc0034@auburn.edu (M.F.C.) † Current address: Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA. The papers published in this Special Issue represent only a glimpse of the vast diversity of viral infectious diseases, and the complexity of their interactions with the host, that have an impact on human and animal health. Yet, in our opinion, these papers greatly contribute to the scientific knowledge that is crucially needed for their comprehension and control. In this Special Issue we expanded our knowledge on avian influenza (AI) viruses. We learned that North American duck-origin H7N9 low-pathogenic AI (LPAI) virus infecting chickens can result in polymorphic mutations in multiple gene segments, indicating that waterfowl-origin viruses can readily jump between avian species and spread in poultry populations [1]. We also discovered that mandarin ducks and pigeons play a crucial role in the spread of zoonotic clade 2.3.4.4 H5N6 highly pathogenic AI (HPAI) viruses, which circulate in multiple continents [2]. Molecular characterization of H6N2 LPAI viruses from Citation: Bertran, K.; Cortey, M.; different countries revealed the importance of genetic surveillance of circulating viruses Criado, M.F. Special Issue “Viral to improve our knowledge about virus transmission dynamics in natural hosts, virus Shedding and Transmission in Zoonotic Diseases”. Viruses 2022, 14, evolution, and zoonotic potential [3]. Finally, a high-quality, greatly comprehensive review 1190. https://doi.org/10.3390/ explored the complexities of airborne transmission of H9N2 viruses in mammals, with a v14061190 special focus on the molecular characteristics of the hemagglutinin [4]. Winged animals, both birds and mammals, were featured for viral diseases other than Received: 9 May 2022 influenza. We learned that previous exposure to Usutu virus partially protects magpies Accepted: 13 May 2022 against lethal challenge with West Nile virus, while still allowing for transmission, with Published: 30 May 2022 crucial consequences for the ecology of these viruses [5]. Finally, the study of astrovirus Publisher’s Note: MDPI stays neutral infection in a colony of Reunion free-tailed bats suggests that these bats can spill over the with regard to jurisdictional claims in virus to other hosts sharing the same habitat, which includes livestock and humans [6]. published maps and institutional affil- We would like to acknowledge all the authors that contributed to this Special Issue. iations. By studying the intricacies of viral shedding and transmission of zoonotic viral infectious diseases, we advance in the understanding of their ecology, epidemiology, vaccinology, prevention, and control. Copyright: © 2022 by the authors. Conflicts of Interest: The authors declare no conflict of interest. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Viruses 2022, 14, 1190. https://doi.org/10.3390/v14061190 https://www.mdpi.com/journal/viruses Viruses 2022, 14, 1190 2 of 2 References 1. Chrzastek, K.; Segovia, K.; Torchetti, M.; Killian, M.L.; Pantin-Jackwood, M.; Kapczynski, D.R. Virus Adaptation Following Experimental Infection of Chickens with a Domestic Duck Low Pathogenic Avian Influenza Isolate from the 2017 USA H7N9 Outbreak Identifies Polymorphic Mutations in Multiple Gene Segments. Viruses 2021, 13, 1166. [CrossRef] [PubMed] 2. Jeong, S.; Kwon, J.-H.; Lee, S.-H.; Kim, Y.-J.; Jeong, J.-H.; Park, J.-E.; Jheong, W.-H.; Lee, D.-H.; Song, C.-S. Subclinical Infection and Transmission of Clade 2.3.4.4 H5N6 Highly Pathogenic Avian Influenza Virus in Mandarin Duck (Aix galericulata) and Domestic Pigeon (Columbia livia domestica). Viruses 2021, 13, 1069. [CrossRef] [PubMed] 3. Mercan, Y.; Atim, G.; Kayed, A.E.; Azbazdar, M.E.; Kandeil, A.; Ali, M.A.; Rubrum, A.; McKenzie, P.; Webby, R.J.; Erima, B.; et al. Molecular Characterization of Closely Related H6N2 Avian Influenza Viruses Isolated from Turkey, Egypt, and Uganda. Viruses 2021, 13, 607. [CrossRef] [PubMed] 4. Cáceres, C.J.; Rajao, D.S.; Perez, D.R. Airborne Transmission of Avian Origin H9N2 Influenza A Viruses in Mammals. Viruses 2021, 13, 1919. [CrossRef] [PubMed] 5. Escribano-Romero, E.; Jiménez de Oya, N.; Camacho, M.-C.; Blázquez, A.-B.; Martín-Acebes, M.A.; Risalde, M.A.; Muriel, L.; Saiz, J.-C.; Höfle, U. Previous Usutu Virus Exposure Partially Protects Magpies (Pica pica) against West Nile Virus Disease but Does Not Prevent Horizontal Transmission. Viruses 2021, 13, 1409. [CrossRef] [PubMed] 6. Joffrin, L.; Hoarau, A.O.G.; Lagadec, E.; Köster, M.; Ramanantsalama, R.V.; Mavingui, P.; Lebarbenchon, C. Astrovirus in Reunion Free-Tailed Bat (Mormopterus francoismoutoui). Viruses 2021, 13, 1524. [CrossRef] [PubMed]