A 2-week old baby, Isabelle, is rushed into the emergency department by her frantic parents. She is tachycardic to 220bpm, febrile to 39.5°C, with a widespread, blanching red rash. She is screaming and looks very unwell. She is rushed into a resus bay and the septic workup begins…
- Particularly during the warmer months, parechovirus is an important differential diagnosis in the septic neonate or young infant
- All neonates and most young infants will still need a full septic workup pending culture and PCR results
- Treatment is supportive and no vaccination is available at this stage
History, virology, and overview
Parechovirus was first described in the United States in 1956. Parechoviruses were originally known as echoviruses and thought to be a type of enterovirus. In the 1990s, molecular virology and genotyping advanced sufficiently to note some distinct differences between enteroviruses and the so-called echoviruses, and the latter were reclassified to the current term – parechovirus. They remain related to enteroviruses, within the family Picornaviridae (small RNA viruses).
Parechoviruses have now been detected worldwide, with the first cases in Australia reported in 2013.
Human parechovirus (HPeV) causes a spectrum of disease from asymptomatic infection to severe, potentially life-threatening illness, predominantly in very young infants.
Parechovirus causes a seasonal illness, which typically peaks over summer in warm climates, but occurs year-round in tropical regions.
How is it transmitted?
Transmission is by person to person via contact with respiratory secretions or faeces from an infected individual.
Viral shedding occurs from the pharynx at 3-4 weeks, and in the faeces at 5-6 weeks.
What is the incubation period?
2 to 14 days.
What are the symptoms?
The classical presentation is a sepsis-like illness in a very young infant, with additional features of;
- Severe irritability, in apparent pain
- Erythematous/maculopapular rash (can be quite pronounced)
- Diarrhoea/loose stools
- Marked tachycardia
- Likely due to myocarditis, though typically normal echocardiogram and full recovery
- Abdominal distension
- Usually, normal CSF counts but white matter changes can be seen on MRI in a small number of affected infants
- Myoclonic jerks
- Hepatitis +/- coagulopathy
How should I investigate?
All neonates and most young infants warrant standard full septic workup (bloods, urine, CSF) and commencement of empiric antibiotics on presentation
Bloods including white cell count and inflammatory markers, along with CSF and urine studies, are often normal
Parechovirus PCRs should be sent, with the gold standard sample being stool, but can also be ordered on CSF, throat swab/NPA, and blood (the 2015 NSW Health alert regarding parechovirus requested for stool and CSF to be sent preferentially).
NB: HPeV is NOT detected on the standard enterovirus PCR
What is the treatment?
Most babies will be given empiric antibiotics as per sepsis guidelines until cultures/PCR results available. Some will require respiratory and/or circulatory support.
How long do they take to recover?
The acute illness lasts 4-7 days followed by defervescence and rapid recovery. Most infants recovery fully, even from very severe illness requiring intensive care admission.
Are there potential complications?
Meningoencephalitis with seizures (rare), abdominal complications (volvulus, intussusception, and bowel ischaemia have been reported).
However, a 2015 Australian study (Khatami et al) which reviewed 118 children with parechovirus across 5 NSW hospitals found no significant complications, despite a high proportion of PICU admissions and the fact that a small group of children had MRIs performed showing white matter changes and diffusion restriction.
Long term sequelae unclear at this stage but likely rare.
- Parechovirus is not a notifiable condition
- Young babies should routinely be protected and kept away from persons with any infective symptoms
- Strict hand hygiene and cleaning of surfaces may reduce transmission
McMullan B. Enterovirus and parechovirus infections in Children. Presentation slides.
Khatami A, McMullan BJ, Webber M, Stewart P, Francis S et al. Sepsis-like Disease in Infants Due to Human Parechovirus Type 3 During an Outbreak in Australia. Clin Infect Dis. (2015) 60 (2): 228-236.