Impact of COVID-19 on Respiratory Virus Infections in Children, Japan, 2018-2023.

Background: COVID-19, caused by SARS-CoV-2, was first documented in Japan in January 2020. We previously reported an increased risk of rhinovirus infections among children during the early phase of the COVID-19 pandemic. Here, we assessed the impact of COVID-19 on respiratory virus infections after SARS-CoV-2 spread nationwide.

An outbreak of influenza A(H1N1)pdm09 antigenic variants exhibiting cross-resistance to oseltamivir and peramivir in an elementary school in Japan, September 2024.

An outbreak of influenza A(H1N1)pdm09 viruses exhibiting cross-resistance to oseltamivir and peramivir occurred in Yokohama, Japan, in September 2024. Among 24 students in a class, 11 were diagnosed with influenza or influenza-like illness, and viruses harbouring the NA H275Y and HA Q210H substitutions were isolated from four. Deep sequencing analysis confirmed the clonal spread of these mutants.

Efficacy of an Inactivated Whole-Virus A/Victoria/361/2011 (IVR-165) (H3N2) Influenza Vaccine in Ferrets.

It has been reported that the high-growth reassortant (HGR) A(H3N2) influenza viruses used for split influenza vaccine (SV) production have some amino acid substitutions in hemagglutinin due to egg adaptation during virus propagation, causing antigenic differences between HGR and epidemic viruses. To clarify whether inactivated whole-virus vaccine (WV) derived from the A(H3N2) HGR virus possessing egg adaptation could induce cross-protective immune responses against epidemic A(H3N2) viruses, the efficacy of WV was compared with that of SV in a ferret model. When the ferrets immunized with WV or SV derived from HGR A/Victoria/361/2011 (IVR-165) virus were challenged with the homologous virus A/Victoria/361/2011 (IVR-165) or its original cell-propagated A/Victoria/361/2011 virus, respectively, WV successfully shortened the duration of virus shedding of both challenge viruses, whereas SV shortened only that of the homologous virus, A/Victoria/361/2011 (IVR-165).

Monitoring Influenza C and D Viruses in Patients With Respiratory Diseases in Japan, January 2018 to March 2023.

Background: Influenza viruses can cause zoonotic infections that pose public health risks. Surveillance of influenza A and B viruses is conducted globally; however, information on influenza C and D viruses is limited. Longitudinal monitoring of influenza C virus in humans has been conducted in several countries, but there has been no long-term monitoring of influenza D virus in humans.