Human parechovirus type 3 has been recognized as a cause of pediatric infection, occasionally associated with serious illness, including sepsis and meningitis, particularly among young infants. The aim of this study is to report the first known human parechovirus type 3 outbreak in Portugal.
Descriptive study of an outbreak that occurred between the 8th June to the 12th August 2016. Laboratory diagnosis was made by reverse transcription – polymerase chain reaction in the cerebrospinal fluid and/or in stools. Genotyping was made by reverse transcription – polymerase chain reaction and sequencing in stool samples from infants and family members.
Human parechovirus type 3 infection was detected in seven infants, of which six were male. Median age was 23 days (5 – 52). One had seizures, with a magnetic resonance imaging scan showing white matter diffusion restriction. The mean duration of admission was 5.6 days (3 – 11), with favourable outcome in all. In three cases there were symptomatic close family members. Human parechovirus type 3 was identified in the stools of three mothers.
Even though human parechovirus type 3 infection has been well described in the presented age group, most Portuguese hospitals do not have this laboratory diagnosis. Our results are comparable to those obtained in other countries. Besides detection of the virus in the cerebrospinal fluid, there were no raised local or systemic inflammatory markers.
This study reports the first known outbreak, in infants, of human parechovirus type 3 in Portugal. Although there is no specific treatment, this diagnosis can avoid unnecessary empirical antibiotic treatment and prolonged admissions.

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