Usefulness of BioFire Filmarray Meningitis/Encephalitis Panel for Diagnosis of Human Parechovirus Infection in Infants and Identification of Local Outbreaks

To the Editors: Human parechovirus (PeV) is a major cause of severe illness in neonates and infants, and PeV infection sometimes requires treatment in the intensive care unit.1 Previously, PeV infection could be diagnosed at only a limited number of institutions by polymerase chain reaction assays of stool, plasma or cerebrospinal fluid samples, but now the diagnosis of PeV infection can be made quickly and easily using rapid cartridge-based molecular test panels targeting multiple pathogens [BioFire Filmarray meningitis/encephalitis panel (Filmarray M/E), bioMerieux].2 Here we report 4 cases that were rapidly diagnosed with PeV infection by Filmarray M/E in Japan within a short period. Four infants were admitted to our hospital between July 10, 2023 and August 10, 2023, and diagnosed with the PeV infection by Filmarray M/E. All patients were term neonates, and the age at admission ranged from 14 to 74 days. Fever, tachycardia, mottled skin and abdominal distention were found on admission in all cases. Rash and palmar–plantar erythema were not recognized on admission but appeared 1–3 days after admission in all cases. On laboratory examination, there was no elevation of white blood cell count, C-reactive protein or procalcitonin. Total nucleated cell count in cerebrospinal fluid was not elevated in 3 cases. In 1 case, a cell count was not performed due to a traumatic lumbar puncture. In these cases, apnea, respiratory acidosis and hypotension occurred as severe complications. A 54-day-old girl had no respiratory symptoms except rhinorrhea on admission, but apnea occurred after admission, and she required mechanical ventilation, staying in the intensive care unit for 4 days. A 74-day-old girl had respiratory acidosis on admission, which improved with continuous positive nasal airway pressure. We diagnosed these 4 cases of PeV infection by Filmarray M/E and recognized an outbreak of PeV infection in our area. PeV is prevalent in the summer once every 2 or 3 years, but PeV infection is not a reportable disease in Japan or the United States (or many other countries), and it is important to identify the local prevalence of PeV infection because local outbreaks have been reported.3 In infants with PeV infection, severe symptoms can occur, including sepsis-like syndrome, apnea, seizure and meningitis or encephalitis. In addition to acute illness, neurodevelopment is a concern in infants with PeV infection, and developmental follow-up is needed.4 However, PeV infection is difficult to diagnose based on clinical presentation because there are few specific clinical features. Although rash and palmar–plantar erythema are considered specific to PeV infection in infants, they usually appear 3 days after the onset of fever, as seen in our cases.5 Our cases suggest that Filmarray M/E is a powerful tool for diagnosing PeV infection and identifying local outbreaks. In conclusion, Filmarray M/E is useful as a point-of-care test for diagnosing PeV infection in infants. It enables the recognition of the local prevalence of PeV and the identification of PeV infection as a cause of severe illness and neurodevelopmental concerns.