Language：English   Publishing type：Research paper (scientific journal)  

Data are limited on the incidence of coronavirus disease 2019 (COVID-19) reinfection in children. This population-based cohort study in Niigata, Japan from January to November 2022 demonstrated the incidence of reinfection was 1337/48 099 (2.8%), and the hazard ratio for reinfection in vaccinated children was 0.29 (95% confidence interval, 0.20-0.40).

DOI： 10.1093/jpids/piad093

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Language：English   Publishing type：Research paper (scientific journal)  

BACKGROUND: The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has dramatically altered the clinical profile of pediatric coronavirus disease 2019 (COVID-19). In Japan, we experienced a pandemic of omicron subvariant BA.1/BA.2 from January through June 2022. However, after the emergence of BA.5 in early July 2022, the number of children hospitalized with COVID-19 increased dramatically in Japan. METHODS: We collected data on monthly numbers of cases and clinical characteristics of hospitalized children with COVID-19 in 13 hospitals, the total number of pediatric COVID-19 cases, and COVID-19 vaccination rates in Niigata, Japan, for the period from January 2020 through August 2022. We compared clinical presentation during the periods of BA.1/BA.2 predominance (January-June 2022) and BA.5 predominance (July-August 2022) and estimated vaccine effectiveness (VE) against hospitalization during the BA.5-predominant period. RESULTS: Between January 1, 2020, and August 31, 2022, 49,387 children (19,085 children/100,000 population) were newly diagnosed as having COVID-19, and 393 were hospitalized for COVID-19. Hospitalization for febrile seizure, especially complex seizure, was significantly higher during BA.5 predominance than during BA.1/BA.2 predominance (27.9% vs. 7.0%, P < 0.01). VE against hospitalization during BA.5 predominance was estimated to be 75% (95% confidence interval, 48%-88%, P < 0.01). CONCLUSIONS: The emergence of BA.5 significantly affected children in Japan; the number with complex febrile seizure who required hospitalization was higher than during BA.1/BA.2 predominance. The COVID-19 vaccination rate in children must be increased to prevent hospitalization for COVID-19 and to prepare for current and future variant outbreaks.

DOI： 10.1097/INF.0000000000003894

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The coronavirus disease 2019 (COVID-19) has caused a serious disease burden and poses a tremendous public health challenge worldwide. Here, we report a comprehensive epidemiological and genomic analysis of SARS-CoV-2 from 63 patients in Niigata City, a medium-sized Japanese city, during the early phase of the pandemic, between February and May 2020. Among the 63 patients, 32 (51%) were female, with a mean (±standard deviation) age of 47.9 ± 22.3 years. Fever (65%, 41/63), malaise (51%, 32/63), and cough (35%, 22/63) were the most common clinical symptoms. The median C t value after the onset of symptoms lowered within 9 days at 20.9 cycles (interquartile range, 17-26 cycles), but after 10 days, the median C t value exceeded 30 cycles (p < 0.001). Of the 63 cases, 27 were distributed in the first epidemic wave and 33 in the second, and between the two waves, three cases from abroad were identified. The first wave was epidemiologically characterized by a single cluster related to indoor sports activity spread in closed settings, which included mixing indoors with families, relatives, and colleagues. The second wave showed more epidemiologically diversified events, with most index cases not related to each other. Almost all secondary cases were infected by droplets or aerosols from closed indoor settings, but at least two cases in the first wave were suspected to be contact infections. Results of the genomic analysis identified two possible clusters in Niigata City, the first of which was attributed to clade S (19B by Nexstrain clade) with a monophyletic group derived from the Wuhan prototype strain but that of the second wave was polyphyletic suggesting multiple introductions, and the clade was changed to GR (20B), which mainly spread in Europe in early 2020. These findings depict characteristics of SARS-CoV-2 transmission in the early stages in local community settings during February to May 2020 in Japan, and this integrated approach of epidemiological and genomic analysis may provide valuable information for public health policy decision-making for successful containment of chains of infection.

DOI： 10.3389/fmicb.2021.749149

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A community outbreak of human influenza A(H1N1)pdm09 virus strains was observed in Myanmar in 2017. We investigated the circulation patterns, antigenicity, and drug resistance of 2017 influenza A(H1N1)pdm09 viruses from Myanmar and characterized the full genome of influenza virus strains in Myanmar from in-patients and out-patients to assess the pathogenicity of the viruses. Nasopharyngeal swabs were collected from out-patients and in-patients with acute respiratory tract infections in Yangon and Pyinmana City in Myanmar during January-December 2017. A total of 215 out-patients and 18 in-patients infected with A(H1N1)pdm09 were detected by virus isolation and real-time RT-PCR. Among the positive patients, 90.6% were less than 14 years old. Hemagglutination inhibition (HI) antibody titers against A(H1N1)pdm09 viruses in Myanmar were similar to the recommended Japanese influenza vaccine strain for 2017-2018 seasons (A/Singapore/GP1908/2015) and WHO recommended 2017 southern hemisphere vaccine component (A/Michigan/45/2015). Phylogenetic analysis of the hemagglutinin sequence showed that the Myanmar strains belonged to the genetic subclade 6B.1, possessing mutations of S162N and S164T at potential antigenic sites. However, the amino acid mutation at position 222, which may enhance the severity of disease and mortality, was not found. One case with no prior history of oseltamivir treatment possessed H275Y mutated virus in neuraminidase (NA), which confers resistance to oseltamivir and peramivir with elevated IC50 values. The full genome sequence of Myanmar strains showed no difference between samples from in-patients and out-patients, suggesting no additional viral mutations associated with patient severity. Several amino acid changes were observed in PB2, PB1, and M2 of Myanmar strains when compared to the vaccine strain and other Asian strains. However, no mutations associated with pathogenicity were found in the Myanmar strains, suggesting that viral factors cannot explain the underlying reasons of the massive outbreak in Myanmar. This study reported the first detection of an oseltamivir-resistant influenza virus in Myanmar, highlighting the importance of continuous antiviral monitoring and genetic characterization of the influenza virus in Myanmar.

DOI： 10.1371/journal.pone.0229601

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

We investigated the circulation patterns of human influenza A and B viruses in Myanmar between 2010 and 2015 by analyzing full HA genes. Upper respiratory tract specimens were collected from patients with symptoms of influenza-like illness. A total of 2,860 respiratory samples were screened by influenza rapid diagnostic test, of which 1,577 (55.1%) and 810 (28.3%) were positive for influenza A and B, respectively. Of the 1,010 specimens that were positive for virus isolation, 370 (36.6%) were A(H1N1) pdm09, 327 (32.4%) were A(H3N2), 130 (12.9%) B(Victoria), and 183 (18.1%) were B(Yamagata) viruses. Our data showed that influenza epidemics mainly occurred during the rainy season in Myanmar. Our three study sites, Yangon, Pyinmana, and Pyin Oo Lwin had similar seasonality and circulating type and subtype of influenza in a given year. Moreover, viruses circulating in Myanmar during the study period were closely related genetically to those detected in Thailand, India, and China. Phylogeographic analysis showed that A(H1N1) pdm09 viruses in Myanmar originated from Europe and migrated to other countries via Japan. Similarly, A (H3N2) viruses in Myanmar originated from Europe, and disseminated to the various countries via Australia. In addition, Myanmar plays a key role in reseeding of influenza B viruses to Southeast Asia and East Asia as well as Europe and Africa. Thus, we concluded that influenza virus in Myanmar has a strong link to neighboring Asian countries, Europe and Oceania.

DOI： 10.1371/journal.pone.0210550

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