Epidemiologic, clinical, and genetic characteristics of influenza C virus infections among outpatients and inpatients in Sendai, Japan from 2006 to 2020.

BACKGROUND: Influenza C virus is a pathogen that causes acute respiratory illness in children. The clinical information about this virus is limited because of the small number of isolated viruses compared to influenza A or B viruses. METHODS: A total of 60 influenza C viruses were isolated by clinical tests using cell culture methods conducted in one hospital and one clinic during the 15 years from 2006 to 2020. These 60 cases were retrospectively analyzed by comparing outpatients and inpatients. Moreover, isolated viruses were analyzed for genomic changes during the study period. RESULTS: All were younger than 7 years, and 73% of inpatients (19 out of 26) were under 2 years of age. A significant difference was found in the frequency of pneumonia, accounting for 45% and 4% of inpatients and outpatients, respectively. Most of the viruses isolated from 2006 to 2012 belonged to the S/A sublineage of the C/Sao Paulo lineage, but three sublineage viruses, including the S/A sublineage with K190N mutation, S/V sublineage, and C/Kanagawa lineage, have cocirculated since 2014. Moreover, S/A sublineage viruses were undergoing reassortment since 2014, suggesting significant changes in the virus, both antigenically and genetically. Of the 10 strains from patients with pneumonia, 7 were in the S/A sublineage, which had circulated from 2006 to 2012. CONCLUSION: Infants under 2 years of age were more likely to be hospitalized with pneumonia. The genomic changes that occurred in 2014 were suggested to affect the ability of the virus to spread.

Anti-influenza virus principles from Muehlenbeckia hastulata.

Extracts of Chilean medicinal plants were evaluated in vitro for their activities against influenza virus proliferation in MDCK cells. The most potent extract obtained was from Muehlenbeckia hastulata (Polygonaceae), known as Quilo in Chile, from which three active principles were isolated and identified as pheophorbide a (1), hypericin (2) and protohypericin (3). Minimum inhibitory concentration (MIC) values of 42 ng/ml for compound 1, 2.1 ng/ml for compound 2 and 1.5 ng/ml for the authentic hypericin were determined by using an endpoint assay which comprises pre-incubation of serially diluted specimens with a given amount of the influenza virus, incubation of the pre-incubated virus/specimen with MDCK cells and determination of the hemagglutination (HA) titer of the culture supernatant. Compound 3 was easily converted to 2 on exposure to visible light and, in due course, showed an anti-influenza virus activity (3.1 ng/ml) similar to 2. Although compounds 1-3 were previously isolated from other plants, this is the first report of their isolation from M. hastulata. The high content of 1 (0.06% dry weight of whole plant) is noteworthy. In addition, this is the first report on the isolation of compounds 2 and 3 from a plant other than the genus Hypericum.