Avian hepatitis E virus (HEV) is highly variable and has multiple genotypes. Previous studies showed that the current epidemic strain in China is genotype 5, but the relevant detection was only carried out in flocks with hepatic rupture haemorrhage syndrome, which does not mean that other genotypes do not exist. In this study, a broader analysis involving different chicken flocks was performed to understand the epidemic status of avian HEV in China. The results showed that the HEV-positive rate of all samples was 7.92% (78/985), and four different genotypes have been identified by analysing a truncate capsid gene fragment, while the homology between them is about 80%. Two of them are separately known as genotype 3 and genotype 5, while the other two are completely unidentified, indicating that there are multiple genotypes of avian HEV prevalent in China. At the same time, the distribution of these genotypes has no obvious geographical clustering pattern, only slightly different in commercial layers, broilers and some indigenous species. This study shows the genetic diversity of avian HEV in China and reminds us to pay more attention to its variation and evolution.

This editorial manuscript reviews the papers accepted for publication in the Special Issue "DC & Hybrid Microgrids" ofApplied Sciences. This Special Issue, co-organized by the University of Pisa, Italy and ostfold University College in Norway, has collected nine papers from 25 submitted, with authors from Asia, North America and Europe. The published articles provide an overview of the most recent research advances in direct current (DC) and hybrid microgrids, exploiting the opportunities offered by the use of renewable energy sources, battery energy storage systems, power converters, innovative control and energy management strategies.