Sepsis-Like Symptoms from Parechovirus A Type 5 in a Neonate: First Japanese Case and Literature Review.

Parechovirus A (PeV-A) is a significant cause of sepsis-like illnesses in neonates and infants. Although PeV-A3 has a known association with severe diseases, severe cases of PeV-A5 infection have recently been reported. We present herein a case of PeV-A5 infection in a 23-day-old neonate who presented with sepsis-like symptoms, including fever, irritability, abdominal distension, and a reticular rash. An erythematous rash developed and spread from the trunk to the extremities after the patient's admission. Blood cultures were negative, and the patient's symptoms rapidly improved with supportive therapy. Polymerase chain reaction testing of pharyngeal and rectal swabs confirmed PeV-A5 infection, as well as the presence of PeV-A5 in the serum during the acute phase. PeV-A5 RNA was undetectable in serum at follow-up testing, whereas stool specimens showed higher detection sensitivity, indicating that the time from symptom onset and specimen selection influence diagnostic accuracy. Whole-genome analysis suggested a recombinant PeV-A5 strain with structural protein regions similar to those of PeV-A5 and nonstructural regions similar to those of PeV-A3. This genomic feature may explain the patient's clinical presentation resembling that of a PeV-A3 infection. PeV-A5 may cause sepsis-like symptoms in early infancy, the pathogenicity of which may be affected by genetic recombination. Further case studies are required to elucidate the clinical features and pathogenicity of PeV-A5 infection.