Two Cases of Primary Human Parainfluenza Virus 1 Pneumonia in Which Bronchoalveolar Lavage Fluid Yielded Human Parainfluenza Virus 1

Two patients, a 76-year-old woman and 66-year-old woman, presented to our hospital with symptoms of lower respiratory tract infection. Both patients showed chest imaging findings of bilateral ground-glass opacities and consolidations. We initially suspected these patients of having influenza-associated pneumonia and cryptogenic organizing pneumonia, respectively, and performed bronchoalveolar lavage, but only human parainfluenza virus-1 infection was detected by multiplex polymerase chain reaction testing. These findings suggest that pneumonia due to human parainfluenza virus-1 should be included in the differential diagnosis of such cases.