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.

Baloxavir marboxil (BXM) is a novel anti-influenza agent that developed in Japan and inhibit the cap endonuclease specifically, and suggested the more clinical effectiveness in influenza. BXM reduces viral shedding more than do neuraminidase inhibitors (NAIs), and its clinical efficacy is equivalent to that of NAIs but is superior to that of NAIs in the case of type B influenza. BXM does not demonstrate any issues with safety, and treatment with BXM reduces the incidences of complicating sinusitis and bronchitis. Prophylactic administration of BXM inhibits intrafamilial transmission of influenza although low susceptible viruses with a PA/I38X substitution are isolated with a certain frequency following administration of BXM. Finally, In influenza treatment for patients aged 12−19 years and for adult outpatients, BXM can be used with the same recommendation level as oseltamivir.

The pulmonary characteristics of Staphylococcus aureus (S. aureus) co-infection with respiratory viruses, such as SARS-CoV-2 and influenza virus, are still unclear. Case series: Two patients with methicillin-susceptible S. aureus (MSSA) infection in the lungs co-infected with either SARS-CoV-2 or influenza virus are reported. Case 1 was a 66-year-old woman who was admitted with SARS-CoV-2 infection. Her chest X-ray and computed tomography (CT) showed multiple cavity formations with infiltration shadows, and MSSA was detected from her sputum and blood, suggesting COVID-19-related bacterial pneumonia and pulmonary embolism. No catheters had been used, but she had skin eruptions and a history of SARS-CoV-2 vaccination. Ampicillin/sulbactam (ABPC/SBT) was administered, and she finally improved. Case 2 was an 87-year-old man with a history of atopic dermatitis who was admitted with moderate pneumonia, and influenza virus co-infection was found. He showed multiple cavitary shadows, and MSSA was isolated from both his sputum and blood. He was diagnosed with influenza-related bacterial pulmonary embolism. No catheters had been used, but he had a history of influenza vaccination. He was also treated by ABPC/SBT and finally improved. Conclusions: These cases suggest that MSSA showed affinity to the lungs when co-infected with either SARS-CoV-2 or influenza virus, and it presented as septic emboli without catheter use. We should consider MSSA infection when patients have SARS-CoV-2 or influenza virus co-infection, and multiple cavity formation and skin disorders are seen, even though they were vaccinated and no catheters were used.

The pandemic of the SARS-CoV2 (COVID-19) that was declared by the World Health Organization (WHO) on 11 March 2020 is still ongoing. One of the early recommendations from CDC and other international agencies is the seasonal influenza vaccination to decrease the effects and burden of COVID-19 pandemic. This review suggests that during COVID-19 pandemic vaccination against seasonal influenza should be conducted all over the year, even for young age groups, because of several reasons. First, the complications of seasonal influenza, especially pneumonia, could increase the burden on the saturated healthcare systems worldwide. Second, the resemblance of symptoms and signs of both seasonal influenza and COVID-19 will difficult diagnosing and isolation of COVID-19 patients. Third, it has been postulated that there is a cross immunity between seasonal influenza and COVID-19.