Outbreaks of influenza B infection and pneumococcal pneumonia at a mental health facility in Japan

[[[ Background: ]]] Japan has an aging population and an increasing number of patients who reside in long-term care and mental health facilities. Both pneumococcal pneumonia and influenza B infection outbreaks have been observed in these populations, although no reports have described concurrent outbreaks of pneumococcal pneumonia and influenza B infection in these facilities. [[[ Case presentation: ]]] Six patients and two staffs were initially diagnosed with influenza B infection at a mental health facility on March 14, 2015. By March 21, influenza B infection was diagnosed in 26 patients and 10 staff; all individuals received anti-influenza drugs. On March 19, two patients were diagnosed with pneumococcal pneumonia, and seven patients had developed pneumococcal pneumonia by March 24. Six of these seven patients also had influenza B infection. All individuals who developed pneumococcal pneumonia were hospitalized and treated using ampicillin/sulbactam at our hospital, and their symptoms subsequently subsided. Among the seven pneumococcal strains that were frozen and stored, two strains were type 3 and five strains were type 11A/E. Pulsed-field gel electrophoresis testing revealed that each of the serum types were from the same clone. [[[ Conclusion: ]]] It appears that an outbreak of influenza B infection was followed by the spread of multi-clone pneumococcal pneumonia among elderly patients at a mental health facility. Therefore, it may be prudent to use vaccinations to prevent the spread of pneumococcal pneumonia among elderly patients and this diagnosis should be actively considered during outbreaks of influenza infection at elder care facilities.