Cocirculation of Influenza C Viruses with Distinct Internal Genome Constellations in Iwate Prefecture, Japan, in 2016.

Accepted July 19, 2018. J-STAGE Advance Publication July 31, 2018. DOI: 10.7883/yoken.JJID. 2018.204 * Corresponding author: Mailing address: Division of Infectious Diseases and Immunology, Department of Microbiology, School of Medicine, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan. Tel: +81-19651-5111 (ext.5790), Fax: +81-19-908-8025, E-mail: ymuraki@iwate-med.ac. jp initiated a screening for the influenza C virus NP gene in the specimens wherein none of the above-mentioned viruses had been detected. Among the 141 specimens obtained between January 2015 and February 2018, 2 displayed positive results. One sample had been collected in March 2016, from an 18-month-old girl with symptoms of fever (38.9°C) and wheezing, and the other, in May 2016, from a 34-month-old girl who presented with a sore throat and erythema. The 2 samples were inoculated into MDCK cells and/or the amniotic cavity of 8-day-old embryonated chicken eggs and then passaged once in chicken eggs. The obtained amniotic fluids caused agglutination of chicken, but not guinea pig, erythrocytes (data not shown). A hemagglutination-inhibition (HI) test of the fluids using a panel of monoclonal antibodies against the hemagglutinin-esterase-fusion (HEF) protein (7) showed that the HEF antigenicity was identical to that of C/Sao Paulo/378/82 (data not shown). Thus, the isolated viruses were named as influenza C/Iwate/1/2016 and C/Iwate/ 2/2016. To our knowledge, these influenza C virus strains have been isolated in the Iwate Prefecture for the first time since the monitoring of the virus was initiated in 2015. Next, the nucleotide sequences of the complete coding region of the individual RNA segments were determined. Data were analyzed using MEGA version 6.0 (8), and phylogenetic trees for each segment were constructed using the maximum-likelihood method (8), together with 26 representative strains isolated from 1981 to 2014. The HEF genes of both isolates belonged to the C/Sao Paulo lineage (Fig. 1), which was consistent with the results of the HI test. As shown in Fig. 2, the PB2, PB1, P3, NP, M, and NS genes of C/Iwate/1/2016 belonged to the C/ Yamagata/81-related lineage (Y-lineage), Y-lineage, C/ Mississippi/80-related lineage (M-lineage), M-lineage, Y-lineage, and Y-lineage, respectively. In contrast, those of C/Iwate/2/2016 belonged to the M-, Y-, M-, Y-, Y-, The influenza C virus is a causative agent of mild upper respiratory tract illnesses. Additionally, it is known to affect the lower respiratory tract, causing bronchitis and pneumonia, particularly in children less than 2 years old (1–3). Seroepidemiological studies indicate that the virus is ubiquitously distributed in the human population (4,5). However, as only a few laboratories are actively performing surveys of the influenza C virus, its regional distribution is not fully understood. In this study, the unique genetic characteristics of the influenza C viruses isolated in the Iwate Prefecture, Japan, in 2016, have been described. As part of the National Epidemiological Surveillance of Infectious Diseases, Japan, based on the Infectious Diseases Control Law, since 1999 we have been performing virus surveillance using nasopharyngeal swabs collected from pediatric patients who visited sentinel hospitals and clinics in the Iwate Prefecture. The collected swabs were transported to the Iwate Prefectural Research Institute for Environmental Sciences and Public Health. These were examined for the presence of the following viruses using cell culture and reverse transcription polymerase chain reaction (RT-PCR) techniques: the respiratory syncytial virus, human metapneumovirus, parainfluenza virus, rhinovirus, enterovirus, adenovirus, coronavirus, and influenza A and B viruses. In January 2015, using real-time RT-PCR (6), we Jpn. J. Infect. Dis. , 71, 393–395, 2018