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The chikungunya virus (CHIKV) is widespread. In Zhejiang province, China, CHIKV infection is often associated with travelers from tropical and subtropical countries. In the present study, three CHIKV isolates from serum samples of travelers in Zhejiang province in 2019 were sequenced, and phylogenetically analyzed to study their molecular characteristics. Sequence analysis showed that the non-structural protein and the structural protein had 37 and 28 amino acid mutations, respectively; no mutation site was found at the E1-A226 residue, which could increase the adaptability of CHIKV to Aedes albopictus. All three samples carried two mutations, namely, E1-K211E and E2-V264A, which were introduced to Bangladesh around late 2015 and Thailand in early 2017. Phylogenetic analysis revealed that these three CHIKVs were Indian Ocean lineage of the East Africa/Central/South Africa genotype (ECSA) and that the MF773566 strain from Bangladesh (Australia/Bangladesh 2017) had the closest evolutionary relationship. The three CHICKs imported into Zhejiang province in 2019 belonged to the ECSA genotype and had multiple amino acid variation sites. The variation in the three samples provides a certain reference for the subsequent research on CHIKV evolution.

The R294K mutation in neuraminidase (NA) causes resistance to oseltamivir in the avian influenza virus H7N9. Reverse transcription droplet digital polymerase chain reaction (RT-dd PCR) is a novel technique for detecting single-nucleotide polymorphisms. This study aimed to develop an RT-dd PCR method for detecting the R294K mutation in H7N9. Primers and dual probes were designed using the H7N9 NA gene and the annealing temperature was optimized at 58.0 °C. The sensitivity of our RT-dd PCR method was not significantly different from that of RT-qPCR (p = 0.625), but it could specifically detect R294 and 294K in H7N9. Among 89 clinical samples, 2 showed the R294K mutation. These two strains were evaluated using a neuraminidase inhibition test, which revealed that their sensitivity to oseltamivir was greatly reduced. The sensitivity and specificity of RT-dd PCR were similar to those of RT-qPCR and its accuracy was comparable to that of NGS. The RT-dd PCR method had the advantages of absolute quantitation, eliminating the need for a calibration standard curve, and being simpler in both experimental operation and result interpretation than NGS. Therefore, this RT-dd PCR method can be used to quantitatively detect the R294K mutation in H7N9.

Background Sapovirus is an important causative agent of acute gastroenteritis in children. In addition, there are only a few reports on the genotype of Sapovirus in Zhejiang Province. Therefore, we analysed the genotypes of Sapovirus from seven outbreaks in the Zhejiang Province. Methods A total of 105 faecal samples from seven outbreaks of Sapovirus were collected from the Zhejiang Provincial Central for Disease Control and Prevention. The genotype was analysed using RT-PCR to perform Sanger sequencing, and next-generation sequencing was used to obtain a complete genome to analyse the amino acid mutations of the VP1 protein. Results According to the results, we found that there were four genotypes (GI.6, GI.1, GI.2, and GII.5) that were detected, with the higher detection rate of GI.6. Most patients were > 5 years old. Seven outbreaks often occurred in primary school and during the cold season. In addition, based on the alignment outcomes of whole sequences and the amino acid sequence of VP1, strain GI.6 induced outbreaks showed high homology. There were some substitutions in VP1. Conclusion There were diversity in genotypes of Sapovirus in seven outbreaks. And GI.6 might be the main genotype responsible for the Sapovirus outbreak in Zhejiang Province in 2022 with high homology, which might provide a reference for SaV prevention and control.