Legionnaires' disease became widely known following an outbreak of pneumonia in the United States in 1976. It is often caused by infection from artificial water sources such as cooling towers, water supply and heating systems, and recirculating hot tubs. To effectively implement infection prevention measures for Legionnaires' disease, collaboration among healthcare workers, water supply and heating system managers, building hygiene personnel, and other relevant parties is essential. It is important to note that outbreaks of Legionnaires' disease continue to occur frequently both domestically and internationally. While the number of reported cases of Legionnaires' disease in Japan has increased, the mortality rate has decreased but has stabilized at a lower level. Caution is also required as reports have been made in association with disasters and travel, in addition to artificial environmental water.

Respiratory syncytial virus (RSV) is commonly known as a pathogen of the bronchiolitis in children, however, recently also as a pathogen of the severe virus pneumonia in adults, especially elderly persons, and vaccines for elderly persons have been developed. There are two vaccines, such as the vaccines targeted for subgroup A with the adjuvant, and that targeted for both subgroup A and B but not included the adjuvant in Japan. Both vaccines are considered effective to prevent not only the incident of RSV infection/pneumonia, but also the exacerbations of the elderly persons with underlying diseases including chronic cardiopulmonary diseases.

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.