Since the coronavirus disease 2019 (COVID‐19) outbreak, laboratory diagnosis has mainly been conducted using reverse‐transcription polymerase chain reaction (RT‐PCR). Detecting the presence of an infectious virus in the collected sample is essential to analyze if a person can transmit infectious severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). However, there have been no quantitative investigations conducted for infectious SARS‐CoV‐2 in clinical samples. Therefore, in the present study, a rapid and simple focus‐forming assay using the peroxidase‐antiperoxidase technique was developed to quantify infectious SARS‐CoV‐2 titers in 119 samples (n = 52, nasopharyngeal swabs [NPS]; n = 67, saliva) from patients with COVID‐19. Furthermore, the study findings were compared with the cycle threshold (Ct) values of real‐time RT‐PCR. The infectious virus titers in NPS samples and Ct values were inversely correlated, and no infectious virus could be detected when the Ct value exceeded 30. In contrast, a low correlation was observed between the infectious virus titers in saliva and Ct values (r = ‐0.261, p = 0.027). Furthermore, the infectious virus titers in the saliva were significantly lower than those in the NPS samples. Ten days after the onset of COVID‐19 symptoms, the infectious virus was undetectable, and Ct values were more than 30 in NSP and saliva samples. The results indicate that patients whose symptoms subsided 10 days after onset, with Ct values more than 30 in NSP and saliva samples, were less likely to infect others.

Although rubella is epidemic in Indonesia, the phylogenetic profile of circulating rubella virus strains has not been clarified. In 2017, rubella virus was detected in 2 travelers who returned from Indonesia to Japan. These strains were classified into genotype 1E lineage 2, which may be an indigenous strain in Indonesia.

Human norovirus is a predominant etiological agent responsible for acute gastroenteritis across all age groups. Recently, norovirus recombinant strains have been reported as the cause of norovirus outbreaks in several settings and the strains that cause outbreaks mostly belong to the norovirus GII. However, yet, the norovirus GI recombinant strains have never been reported previously in Thailand. The aims of this study were to investigate the genetic recombination and genotype diversity of norovirus GI strains in children hospitalized with acute gastroenteritis in Chiang Mai, Thailand during a period of seven years from 2015 to 2021. A total of 2829 stool specimens were screened for norovirus GI by real-time PCR, and the polymerase and capsid genes were sequenced and analyzed. Of 2829 specimens tested, 12 (0.4%) were positive for norovirus GI. Of these, 7 out of 12 (58.3%) strains were identified as norovirus GI recombinant strains. Among 7 norovirus GI recombinant strains, 3, 3, and 1 were identified as GI.3[P13], GI.5[P4], and GI.6[P11], respectively. The remaining five strains were identified as non-recombinant strains of the GI.4[P4], GI.5[P5], and GI.6[P6] genotypes. The findings highlight the genetic diversity and multiple intergenotype recombinant strains of norovirus GI circulating in children with acute gastroenteritis in Chiang Mai, Thailand from 2015 to 2021. The detection of multiple intergenotype norovirus GI recombinant strains further underscore the complexity of norovirus GI strains circulating in this region.