By Stan Deresinski, MD, FACP, FIDSA
Clinical Professor of Medicine, Stanford University
SYNOPSIS: Parechovirus A3 is a leading cause of meningoencephalitis in infants.
SOURCES: Tao L, Fill MA, Banerjee R, Humphries RM. Notes from the Field: Cluster of parechovirus central nervous system infections in young infants — Tennessee, 2022. MMWR Morb Mortal Wkly Rep 2022;71:977-978.
Centers for Disease Control and Prevention. Recent reports of human parechovirus (PeV) in the United States—2022. https://emergency.cdc.gov/han/2022/han00469.asp
During a 42-day period ending May 24, 2022, a total of 23 previously healthy infants aged 5 days to 3 months with meningoencephalitis due to parechovirus were admitted to the Monroe Carell Jr. Children’s Hospital in the Vanderbilt University Medical Center. As part of standard practice, cerebrospinal fluid (CSF) examination was routinely performed during sepsis evaluation in all infants younger than 1 month of age and in older infants as indicated. The diagnosis of parechovirus infection was made using the BioFire FilmArray Meningitis/Encephalitis Panel.
The median age of the patients was 24 days, and five of them were preterm, having been delivered at 28-36 weeks’ gestation. Thirteen (57%) of the infants were female. Fever, fussiness, and poor feeding were the most frequent symptoms, occurring in 87%, 57%, and 35%, respectively. CSF pleocytosis was detected in only seven patients (32%), and in three of these, CSF was believed to have been contaminated by blood.
The illness was severe enough to require neonatal intensive care unit (NICU) care. Brain magnetic resonance imaging (MRI) was performed in only four infants, and this detected white matter diffusion abnormalities in all. All but two patients recovered without residual complications — one with persistent seizures was expected to have significant developmental delay and another was reported to have possible late-onset hearing loss.
COMMENTARY
Parechovirus is a member of the Picornaviridae family, closely related to enterovirus. It is comprised of four types (A-D), with only A and B affecting humans, with peak incidences in the summer and autumn. Patients 5 months to 5 years of age with infection generally have only a febrile upper respiratory tract infection, often with a skin eruption, but severe illness may occur in those younger than 3 months of age. This may manifest as sepsis syndrome, seizures, and meningitis/meningoencephalitis.
In a prospective study of 461 hospitalized infants younger than 90 days of age at Children’s Mercy Hospital in Kansas City in 2011-2012, enterovirus was detected in 35 patients (7.6%) while parechovirus A was found in 40/461 patients (8.7%) — with 32 of the 40 being parechovirus A3.1 Enterovirus of all types was detected in 7.6%. Screening of maternal throat swabs detected parechovirus A in 9/427, and eight of the nine infants had meningoencephalitis due to the virus. Infected individuals, both symptomatic and asymptomatic, can transmit parechovirus via the fecal-oral and respiratory routes. Shedding from the upper respiratory tract may persist for one to three weeks and from the gastrointestinal tract for as long as six months.
CSF findings in parechovirus meningoencephalitis often are normal, in contrast to those caused by enterovirus, and, in particular, pleocytosis usually is absent. In neonates with encephalitis, MRI findings often include restricted subcortical and periventricular diffusion together with signal abnormalities in the corpus callosum as well as “swollen” thalami.2
Along with enterovirus, parechovirus A3 was the leading cause of central nervous system infection in infants and young children. The increasing number of reports is of concern but may be due to the widespread availability of multiplex diagnostic methods for testing CSF, rather than increasing prevalence.
REFERENCES
- Klatte JM, Harrison CJ, Pate B, et al. Maternal parechovirus A (PeV-A) shedding, serostatus, and the risk of central nervous system PeV-A infections in infants. J Clin Virol 2021;142:104939.
- Tierradentro-García LO, Zandifar A, Kim JDU, Andronikou S. Neuroimaging findings in parechovirus encephalitis: A case series of pediatric patients. Pediatr Neurol 2022;130:41-45.
