Background: Severe COVID-19 patients who received ventilator management were not very rare even when the omicron variant became dominant, but the clinical characteristics of these patients are still unclear. Methods: The clinical characteristics of severe COVID-19 patients requiring ventilator management were retrospectively investigated from January 2023 to December 2023. Results: Severe COVID-19 patients who received ventilator management accounted for 11 of 275 (4.2%) patients during the omicron variant period. Their mean age was 70.7 (51-85) years, and males were predominant. Ten of eleven (91.7%) patients were managed in the emergency department and had underlying diseases, including chronic lung/heart/kidney diseases and neurological diseases. However, only 4 of 11 (36.4%) had a clear history of vaccination. The patients showed a positive SARS-CoV-2 antigen titer of 3305.7 (12.9-20912). All 11 patients were treated with remdesivir and dexamethasone, and 5 (45.5%) also received sotrovimab. Pathogenic bacteria were isolated from 7 of 11 (63.6%) patients, and all 11 patients were treated with antibiotics. Only 3 of 11 (27.3%) patients were managed using extracorporeal membrane oxygenation (ECMO), but 9 of 11(81.8%) patients survived. Conclusions: These data suggest that severe COVID-19 patients who required ventilator management were less-vaccinated, elderly patients with underlying disease. These patients were treated successfully using antiviral agents, steroids, neutralizing antibodies, and antibiotics, with a few also treated using ECMO in the omicron era.

Respiratory virus co-infections have been suggested to happen frequently and exacerbate patients’ conditions, but little is known about the detailed rates and the combinations of viruses during the COVID-19 pandemic period. A total of 255 symptomatic patients who underwent multiplex PCR tests were analyzed, and it was found that 6 (6/255=2.4%) patients were infected with multiple viruses. The patients ranged in age from 1 to 38 years, and one female patient was pregnant. Of the 6 patients, 4 had fever, and 5 had human rhinovirus/enterovirus and another virus. These data suggested that the rate of respiratory virus co-infection was low, and the combination of SAS-CoV-2 and other viruses was rare even during the COVID-19 pandemic.

Background: The titers of SARS-COV-2 antigens are frequently used as markers of viral activity and threshold for release from quarantine and treatment. COVID-19 patients were treated with several antiviral agents, including remdesivir (RDV) and ensitrelvir (ESV), which is a novel anti-SARS-CoV-2 agent recently suggested to have strong antiviral activity. Cases: We present the cases of two patients whose SARS-CoV-2 antigens were successfully decreased by oral administration of ESV after they could not be decreased by RDV drip infusion. Case 1 was a 74-year-old man who was admitted with SARS-CoV-2 infection and had been infected by the virus a month earlier and relapsed twice. He had been treated with rituximab for diffuse B cell lymphoma and not received vaccination for SARS-CoV-2. RDV was administered intravenously two weeks earlier and again 4 days earlier, but it failed to control the infection, and he was transferred to our hospital (day 1). Intravenous RDV was restarted on day 1, but viral antigens remained high until day 5. The RDV was then switched to oral ESV, and viral antigen titers were successfully decreased on days 8, 10, and 12. Case 2 was an 81-year-old man who was admitted with SARS-CoV-2 infection on day 0. He had heart failure and diabetes mellitus, and had not received vaccination for SARS-CoV-2. Intravenous RDV was started on day 1, but viral antigens were still high until day 8. He was then switched from RDV to oral ESV, and viral antigen titers were successfully decreased on day 11. Conclusions: These cases suggest that ESV might be more effective than RDV for reducing viral activity, and it is easy to administer orally.

The initial omicron SARS-CoV-2 subvariants, BA.1 and BA.2 (BA.1.2), were progressively displaced by BA.5in Japan in 2022. In the BA.5-dominant period, there were significantly more healthcare staff infected by nosocomial contact with persons with confirmed SARS-CoV-2 infection than those infected by household contact, compared with the BA.1.2-dominant period. The staff infected via nosocomial contact included non-patient-facing staff, in the BA.5-dominant period, although they did not become infected by SARS-CoV-2 through nosocomial contact in the BA.1.2-dominant period. These data suggest the importance of infection control and care for non-patient-facing staff, in the same way as for patient-facing staff.

Central line-associated bloodstream infections (CLABSIs) are important hospital-acquired infections that are related to increased mortality in cardiac intensive care units (CICUs). To determine the risk factors for CLABSIs, a case-control study was conducted in the CICU of our hospital. Emergency surgery (odds ratio: 9.6, 95% confidence interval: 1.633-56.926) was the strongest risk factor comparing the case group (n=11) to the control group (n=22). In addition, the indwelling period was significantly longer in the case group than in the control group (median 9 days versus 7 days, p=0.004). An intervention for the insertion of central lines was then started, with 1) thorough use of chlorhexidine-impregnated dressings (also known as chlorhexidine patches, CHG patches) in the insertion of central lines before emergency surgery, and 2) exchange of the central line 7 days after emergency surgery. After the intervention, the CLABSI incidence rate decreased from 6.8 to 0.8/1,000 device-days. These data suggest the usefulness of CHG patches and the importance of the early exchange of central lines in the CICU in patients following emergency surgery.

Background: COVID-19-related pneumonia was initially rare, though influenza-related pneumonia is well known as a severe complication of influenza. However, COVID-19-related pneumonia may be increasing since the omicron variant of COVID-19 appeared. Methods: The clinical differences between COVID-19-related and influenza-related pneumonia patients were retrospectively investigated in patients hospitalized from January 2022 to December 2023. Results: COVID-19-related and influenza-related pneumonias were found in 46 of 285 (15.8%) and 6 of 12 (50.0%) patients, respectively (p<0.001). Their mean ages were 75.5 (45-93) years and 53.8 (19-73) years in COVID-19-related and influenza-related pneumonia cases, respectively (p=0.002). Aspiration pneumonia was more common in COVID-19-related pneumonia (28/46=60.9%) than in influenza-related pneumonia patients, and it was treated by sulbactam/ampicillin (31/46=67.4%). The influenza-related pneumonia patients were more often infected in the work place (2/6=33.3%) and not vaccinated (4/6=66.7%), compared with COVID-19-related patients. Death occurred in 7 of 46 (15.2%) COVID-19 patients, but none of 6 influenza-infected patients died. Conclusions: These data suggest that COVID-19-related pneumonia presented as aspiration pneumonia in older patients, although influenza-related pneumonia was more common in younger and non-vaccinated patients and might be associated with immune mechanisms during the omicron variant surge era.

The initial omicron (B.1.1.529) severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) subvariants, BA.1 and BA.2 (BA.1/2), were progressively displaced by BA.5 in Japan, which showed not only higher transmittivity and less pathogenicity, but also differences in antibiotic use according to the difference in the clinical course of BA.5 compared with BA.1/2 infections. BA.5 patients received more antibiotics, especially ampicillin/sulbactam, although ceftriaxone and meropenem were used significantly in the BA.1/2 period. These data suggest an increased incidence of aspiration pneumonia in elderly patients in the BA.5 period, and we should consider changing the management tactics for COVID-19.