Asymptomatic children might transmit human parechovirus type 3 to neonates and young infants

Diagnosis, management, and outcomes of parechovirus infections in infants: an overview

Parechovirus A (PeV-A) infections have been detected with increasing frequency in US infants under 6 months of age, leading to a Centers for Disease Control and Prevention (CDC) health advisory in July 2022. Clinicians are advised to consider PeV-A laboratory testing of blood and cerebrospinal fluid when infants present with unexplained fever, sepsis-like illness, or neurological issues. Clinical laboratories are encouraged to offer in-house molecular testing for PeV-A to avoid diagnostic delays, unnecessary use of antibiotics, and prolonged hospitalization of infants presenting with sepsis-like illness. While data are evolving on potential neurodevelopmental sequelae after PeV-A infant central nervous system infections, most infected infants return to baseline health for age. This review examines the PeV-A literature with a focus on PeV-A3, including aspects of epidemiology, clinical presentations/management, laboratory diagnostics, genotyping, and post-infectious sequelae related to PeV-A infections in infants.

An outbreak investigation of parechovirus-A3 in a newborn nursery

OBJECTIVE

To investigate parechovirus-A3 (PeV-A3) transmission in a newborn nursery, after encountering 3 neonates with fever and rash.

DESIGN

An observational study.

SETTING

At a newborn nursery at the general hospital in Hyogo, Japan.

PARTICIPANTS

Symptomatic neonates and their family members, and asymptomatic neonates born during the same period.

METHODS

PCR assays for PeV-A and genotyping were used for the investigation of PeV-A3. Preserved umbilical cords were used to identify the route of transmission.

RESULTS

PeV-A3 infection was confirmed in the three symptomatic neonates. The index case had fever and rash, and the 2 neonates treated later became symptomatic and had serum, cerebrospinal fluid, and stool specimens that were positive for PeV-A3 on PCR. The umbilical cord of the index case was positive for PeV-A3 on PCR. The family members of the index case, including the mother, were asymptomatic before delivery. The older sister and cousin of the PeV-A3-infected neonate had positive PCR results. The sequence analysis suggested 2 possible transmission routes: vertical and horizontal transmission in a newborn nursery and/or a family outside the hospital. The incubation period of PeV-A3 infection was estimated to be 1-3 days (maximum, 7 days).

CONCLUSION

Horizontal transmission of PeV-A3 was confirmed in a newborn nursery. Vertical transmission was suggested by the detection of RNA in an umbilical cord sample from the index case. These observations indicate that PeV-A3 can be horizontally transmitted in a newborn nursery and that special caution is required to prevent healthcare-associated transmission of PeV-A3.

Molecular Evolution and Epidemiology of Parechovirus-A3 in Japan, 1997-2019

Parechovirus-A3 (PeV-A3), first reported in 2004 in Japan, is an emerging pathogen that causes sepsis and meningoencephalitis in neonates and young infants. Although PeV-A3 has been identified worldwide, its epidemiological characteristics differ by region. To investigate the molecular evolution and epidemiology of PeV-A3, we performed genetic analyses of 131 PeV-A3 strains from the years 1997-2019 in Niigata, Japan. During 2016-2019, annual numbers remained steady, in contrast to the PeV-A3 epidemic interval of every 2-3 years that was observed in Japan from 2006. Bayesian evolutionary analysis of the complete viral protein 1 region revealed alternate dominant clusters during years of PeV-A3 epidemics. The branch including the oldest and first isolated PeV-A3 strains in Japan has been disrupted since 2001. The year of PeV-A3 emergence was estimated to be 1991. Continuous surveillance with genetic analyses of different regions will improve understanding of PeV-A3 epidemiology worldwide.

An atypical case of Kawasaki disease with severe pneumonia in a neonate

BACKGROUND

Kawasaki disease (KD) is an acute, febrile, systemic vasculitis of unknown etiology that primarily affects the coronary arteries and generally occurs at around 1 year of age. Although the diagnosis of KD is generally not difficult, it is challenging in cases of incomplete KD lacking characteristic clinical manifestations. The incidence of incomplete KD is higher in infants younger than 6 months of age. Pneumonia is an extremely rare complication of KD and can be misinterpreted as atypical pneumonia rather than KD. Herein, we report a neonate with atypical KD and severe pneumonia who required mechanical ventilation.

CASE PRESENTATION

Japanese one-month-old infant had only fever and rash on admission (day 1), and he was transferred to the intensive care unit for severe pneumonia on day 2. Although pneumonia improved following intensive care, he was diagnosed with KD on day 14 because of emerging typical clinical manifestations such as fever, bulbar nonexudative conjunctival injection, desquamation of the fingers, and coronary artery aneurysm. KD symptoms improved after three doses of intravenous immunoglobulin plus cyclosporine. However, small coronary aneurysms were present at the time of discharge. In a retrospective analysis, no pathogens were detected by multiplex real-time PCR in samples collected at admission, and the serum cytokine profile demonstrated prominent elevation of IL-6 as well as elevation of neopterin, sTNF-RI, and sTNF-RII, which suggested KD.

CONCLUSIONS

The patient's entire clinical course, including the severe pneumonia, was caused by KD. As in this case, neonatal KD may exhibit atypical manifestations such as severe pneumonia requiring mechanical ventilation.

Characterization of Pathogenesis and Inflammatory Responses to Experimental Parechovirus Encephalitis

Human parechovirus type 3 (PeV-A3) infection has been recognized as an emerging etiologic factor causing severe nerve disease or sepsis in infants and young children. But the neuropathogenic mechanisms of PeV-A3 remain unknown. To understand the pathogenesis of PeV-A3 infection in the neuronal system, PeV-A3-mediated cytopathic effects were analyzed in human glioblastoma cells and neuroblastoma cells. PeV-A3 induced interferons and inflammatory cytokine expression in these neuronal cells. The pronounced cytopathic effects accompanied with activation of death signaling pathways of apoptosis, autophagy, and pyroptosis were detected. A new experimental disease model of parechovirus encephalitis was established. In the disease model, intracranial inoculation with PeV-A3 in C57BL/6 neonatal mice showed body weight loss, hindlimb paralysis, and approximately 20% mortality. PeV-A3 infection in the hippocampus and cortex regions of the neonatal mouse brain was revealed. Mechanistic assay supported the in vitro results, indicating detection of PeV-A3 replication, inflammatory cytokine expression, and death signaling transduction in mouse brain tissues. These in vitro and in vivo studies revealed that the activation of death signaling and inflammation responses is involved in PeV-A3-mediated neurological disorders. The present results might account for some of the PeV-A3-associated clinical manifestations.

Maternal parechovirus A (PeV-A) shedding, serostatus, and the risk of central nervous system PeV-A infections in infants

BACKGROUND

Parechovirus A (PeV-A) has emerged as a leading cause of infant central nervous system (CNS) infections. Risk factors associated with infant acquisition of PeV-A are not well understood.

METHODS

We conducted prospective PeV-A/enterovirus (EV) CNS infection surveillance, enrolling 461 hospitalized infants <90 days old who underwent sepsis evaluations and lumbar puncture during 2011-2012. Infants were grouped by RT-PCR detection of PeV-A, EV, or neither virus (Neg) in CSF. We collected demographic/clinical data and tested specimens from all infants. For 427 mothers, we collected demographic/clinical data and evaluated PeV-A3 and EV shedding, and PeV-A3 neutralizing antibody for 147 mothers.

RESULTS

PeV-A was detected in 40 infants (8.7%), 4 in 2011 and 36 in 2012. EV was detected in 35 infants (7.6%), 16 in 2011, and 19 in 2012. PeV-A infected infants presented with irritability, abdominal discomfort, fever, and tachycardia, plus both lymphopenia and absence of CSF pleocytosis which help differentiate PeV-A from EV CNS infection. PeV-A was detected in 9/427 maternal throat swabs; eight of their infants also had PeV-A CNS infection. Infants whose mothers had PeV-A3-positive throat swabs were more likely to be PeV-A3-positive than infants whose mothers had negative throat swabs (relative risk [RR], 13.4 [95% CI, 8.6 - 20.7]). Maternal PeV-A3 seropositivity decreased with increasing maternal age. Mothers of PeV-A-positive infants had lower median PeV-A3 neutralizing titers and were more likely seronegative.

CONCLUSIONS

Maternal viral shedding, serostatus and neutralization titers appear to be important factors in infant PeV-A3 CNS infections.

HPeV3-associated acute encephalitis/encephalopathy among Japanese infants

OBJECTIVE

The current study aimed to identify and compare the clinical characteristics of human parechovirus type 3 (HPeV3)-associated acute encephalitis/encephalopathy (HPeV3E/E) between infants with abnormal brain magnetic resonance imaging (MRI) findings (typical, or MRI-positive HPeV3E/E) and those with MRI-negative findings (MRI-negative HPeV3E/E).

METHODS

This is a retrospective study on patients with HPeV3 infection, and a two-step questionnaire survey performed on 837 hospitals in Japan between 2014 and 2016.

RESULTS

We identified 240 infants with HPeV3 infection, of which 34 had been clinically-diagnosed HPeV3E/E (cHPeV3E/E). However, detailed clinical data were provided by 32 of the 34 patients. Among these 32, 23 had undergone MRI and were categorized into two groups, MRI-positive (n = 17) and -negative (n = 6). There were no significant intergroup differences in clinical lab results or symptoms, except for gastrointestinal symptoms that were only present in the MRI-negative patients. The MRI-positive group showed white matter involvement on brain MRI during the acute phase, and 8 patients presented with lesions on follow-up MRI. Furthermore, 4 (50%) of the 8 patients had neurological sequelae.

CONCLUSION

Clinical characteristics of cHPeV3E/E patients with and without lesions on brain MRI showed no significant differences. Therefore, considering the difficulty in distinguishing febrile infants with cHPeV3E/E from those with a sepsis-like illness, during an HPeV3 infection epidemic, it is imperative to frequently perform brain MRI in febrile infants presenting with severe disease for the early diagnosis of HPeV3E/E presenting with brain lesions.

Parechovirus A Infections in Healthy Australian Children During the First 2 Years of Life: A Community-based Longitudinal Birth Cohort Study

Background

Hospital-based studies identify parechovirus (PeV), primarily PeV-A3, as an important cause of severe infections in young children. However, few community-based studies have been published and the true PeV infection burden is unknown. We investigated PeV epidemiology in healthy children participating in a community-based, longitudinal birth cohort study.

Methods

Australian children (n = 158) enrolled in the Observational Research in Childhood Infectious Diseases (ORChID) study were followed from birth until their second birthday. Weekly stool and nasal swabs and daily symptom diaries were collected. Swabs were tested for PeV by reverse-transcription polymerase chain reaction and genotypes determined by subgenomic sequencing. Incidence rate, infection characteristics, clinical associations, and virus codetections were investigated.

Results

PeV was detected in 1423 of 11 124 (12.8%) and 17 of 8100 (0.2%) stool and nasal swabs, respectively. Major genotypes among the 306 infection episodes identified were PeV-A1 (47.9%), PeV-A6 (20.1%), and PeV-A3 (18.3%). The incidence rate was 144 episodes (95% confidence interval, 128–160) per 100 child-years. First infections appeared at a median age of 8 (interquartile range, 6.0–11.7) months. Annual seasonal peaks changing from PeV-A1 to PeV-A3 were observed. Infection was positively associated with age ≥6 months, summer season, nonexclusive breastfeeding at age <3 months, and formal childcare attendance before age 12 months. Sole PeV infections were either asymptomatic (38.4%) or mild (32.7%), while codetection with other viruses in stool swabs was common (64.4%).

Conclusions

In contrast with hospital-based studies, this study showed that diverse and dynamically changing PeV genotypes circulate in the community causing mild or subclinical infections in children.

Parechovirus can cause severe illnesses in children. However, studies focus mainly on hospitalized populations. True disease burden in the community remains largely unknown. From our community-based cohort, we found diverse parechovirus genotypes in the community, causing mild or subclinical infections in children.

Proposal for the Recognition of a New Disease Concept from Japan: Parechovirus A3-Associated Myalgia

Parechovirus A3 (PeVA3) was first reported in 2004 and has been recognized as a causative agent of mild and severe infectious diseases in children. We first reported an outbreak of PeVA3-associated myalgia (PeVA3-M) in Yamagata, Japan, in 2008. We have repeatedly observed PeVA3-M cases in 2011, 2014, and 2016, and identified the first child case in 2014. Reports of PeVA3-M have increased since 2014, indicating that the recognition of PeVA3-M has spread across Japan. The findings showed that PeVA3-M commonly occurs among adults aged 30-40 years, particularly in males. Elevation of creatinine phosphokinase, C-reactive protein, and myoglobin, as well as magnetic resonance imaging findings, suggest inflammation of the muscles and/or fascia of the four limbs. Patients recover within 1-2 weeks without any sequelae. A longitudinal molecular epidemiological study in Yamagata revealed that PeVA3 strains cause a variety of diseases, ranging from mild to severe, including PeVA3-M, in subjects ranging from neonates to adults, irrespective of their genetic cluster. As PeVA3-M has not yet been reported abroad, more widespread recognition of PeVA3-M as an emerging disease is important. We hope this review will help clinicians and researchers in understanding PeVA3-M and therefore advance related research in Japan as well as around the world.

Human parechovirus are emerging pathogens with broad spectrum of clinical syndromes in adults

Parechoviruses are emerging pathogens of humans often affecting the pediatric age group, with a growing line of evidence implicating them as agents of a broad spectrum of clinical syndromes in adults. However, because many clinicians are not familiar with the manifestation of the infections, they are not included in the list of diagnostic pathogens. Furthermore, due to the indistinguishable feature of the infection compared with other common pathogens, a large number of cases are likely to go unchecked. Some may develop asymptomatic infection and recover without overt clinical disease. In this manuscript, we reviewed available literature on parechovirus infection in adult and summarized information relating to epidemiology, clinical manifestation, laboratory diagnosis, and therapeutics. The information provided should help in early case detection and support an evidence-based clinical decision.

Association Between Neutralizing Antibody Titers against Parechovirus A3 in Maternal and Cord Blood Pairs and Perinatal Factors

BACKGROUND

Parechovirus A3 (PeV-A3) is a pathogen that causes severe infectious diseases such as sepsis and meningoencephalitis in neonates and young infants. In this study, we aimed to measure the neutralizing antibody titer (NAT) against PeV-A3 in paired maternal and cord blood samples and to clarify the serum epidemiology of PeV-A3 and the association between the NAT and perinatal factors.

METHODS

NATs against PeV-A3 were measured in 1033 mothers (maternal and cord blood pairs; total of 2066 samples) who delivered their infant in Fukushima Prefecture between December 2013 and June 2014. RD-18S cells were used to measure NATs against PeV-A3. The association between NATs against PeV-A3 in maternal and cord blood and perinatal factors was determined using multivariate logistic regression analysis.

RESULTS

The median gestational age of the infants was 39 weeks 4 days (interquartile range, 38 weeks 4 days to 40 weeks 3 days). The NATs against PeV-A3 in maternal blood and in cord blood were almost the same. The proportion of samples assigned to the low-titer group (NAT ≤ 1:16) was approximately 70%, and the proportion of samples assigned to the high-titer group tended to increase with gestational age. The high-titer rate and geometric mean titers decreased with increased maternal age.

CONCLUSIONS

Cord blood indicates that neonates born at a lower gestational age and older mothers have a low NAT against PeV-A3. Thus, more attention should be paid to the onset of severe PeV-A3 disease in such neonates and young infants.

Intrafamilial Transmission of Parechovirus A and Enteroviruses in Neonates and Young Infants

BACKGROUND

Parechovirus A (PeV-A) is an important cause of sepsis and meningoencephalitis in neonates and young infants. Thus, identifying the source of PeV-A is essential for prevention; however, little is known regarding the spread of PeV-A among family members of PeV-A-infected neonates and young infants.

METHODS

In this prospective study, we evaluated stool samples from family members of PeV-A-infected neonates and infants younger than 4 months who presented with sepsis, meningoencephalitis, or both in Niigata, Japan, in 2016. Because of a simultaneous outbreak, enteroviruses (EVs) were also evaluated during this period. Real-time polymerase chain reaction followed by sequence analysis was used for viral diagnosis using serum and/or cerebrospinal fluid samples.

RESULTS

Among 54 febrile patients, the stool samples of 14 (26%) and 12 (22%) patients tested positive for PeV-A and EV, respectively. Stool samples from 54 family members (38 adults and 16 children) of 12 PeV-A-infected patients were available. The rate of PeV-A positivity in these samples was higher among the children (88% [14 of 16]) than the adults (34% [13 of 38]). Among family members with a PeV-A-positive stool sample, 29% (4 of 14) of the children and 77% (10 of 13) of the adults were asymptomatic. Similarly, among 53 stool samples from family members (31 adults and 22 children) of 11 EV-infected patients, the rate of EV positivity in the stool samples was higher among the children (91% [20 of 22]) than among the adults (42% [13 of 31]). The asymptomatic-patient rates were 45% (9 of 20) among the children and 85% (11 of 13) among the adults in family members with EV-positive stool.

CONCLUSIONS

Similar to EVs, PeV-A was detected frequently in stool samples from family members of PeV-A-infected patients. Among family members with PeV-A-positive stool, adults were more likely than children to be asymptomatic and therefore could be an important source of PeV-A infection.

Parechovirus A Pathogenesis and the Enigma of Genotype A-3

Parechovirus A is a species in the Parechovirus genus within the Picornaviridae family that can cause severe disease in children. Relatively little is known on Parechovirus A epidemiology and pathogenesis. This review aims to explore the Parechovirus A literature and highlight the differences between Parechovirus A genotypes from a pathogenesis standpoint. In particular, the curious case of Parechovirus-A3 and the genotype-specific disease association will be discussed. Finally, a brief outlook on Parechovirus A research is provided.

Polymerase chain reaction for human parechovirus on blood samples improves detection of clinical infections in infants

Human parechovirus (HPeV) is an emerging pathogen for infants. Improved diagnostics are needed due to the non-specific clinical presentation. Real-time reverse transcription polymerase chain reaction (RT-PCR) on blood samples may be an adjunct to diagnosis. A retrospective cohort of HPeV-affected infants was used to assess sensitivity and specificity of a HPeV RT-PCR on blood and cerebrospinal fluid (CSF). As a secondary analysis, the Ct value of the PCR results was compared to clinical correlates of severity. Between 2017 and 2018 blood samples were obtained from 97 infants of whom 44 had HPeV clinical and laboratory proven infection. Eighty-three concurrent CSF samples were available. Sensitivity was 93.3% [95% CI 82-99] for blood HPeV RT-PCR and 85% [95% CI 73.9-96.1] for CSF HPeV RT-PCR. Blood HPeV RT-PCR Ct values < 25 cycles were associated with age < 28 days and < 3 days of symptoms. No statistical associations were identified between potential clinical markers of severity and Ct value. HPeV RT-PCR on blood is a valuable adjunct to diagnostic testing for acute HPeV-related illness in infants. Results can be expected to be robust until at least day 5 of symptoms, with optimal sampling occurring close to onset of symptoms.

Human Parechovirus 3 in Infants: Expanding Our Knowledge of Adverse Outcomes

BACKGROUND

Human parechovirus particularly genotype 3 (HPeV3) is an emerging infection affecting predominantly young infants. The potential for neurologic sequelae in a vulnerable subset is increasingly apparent. A review of 2 epidemics of human parechovirus (HpeV) infection in 2013 and in 2015 in Queensland, Australia, was undertaken, with an emphasis on identifying adverse neurodevelopmental outcome.

METHODS

All hospitalized cases with laboratory-confirmed HPeV infection between October 2013 June 2016 were identified. Clinical, demographic, laboratory and imaging data were collected and correlated with reported developmental outcome.

RESULTS

Laboratory-confirmed HPeV infections were identified in 202 patients across 25 hospitals; 86.6% (n = 175) were younger than 3 months 16.3% (n = 33) received intensive care admission. Of 142 cerebrospinal fluid samples which were HPeV polymerase chain reaction positive, all 89 isolates successfully genotyped were HPeV3. Clinical information was available for 145 children; 53.1% (n = 77) had follow-up from a pediatrician, of whom 14% (n = 11) had neurodevelopmental sequelae, ranging from hypotonia and gross motor delay to spastic quadriplegic cerebral palsy and cortical visual impairment. Of 15 children with initially abnormal brain magnetic resonance imaging, 47% (n = 7) had neurodevelopmental concerns, the remainder had normal development at follow-up between 6 and 15 months of age.

CONCLUSIONS

This is the largest cohort of HPeV3 cases with clinical data and pediatrician-assessed neurodevelopmental follow-up to date. Developmental concerns were identified in 11 children at early follow-up. Abnormal magnetic resonance imaging during acute infection did not specifically predict poor neurodevelopmental in short-term follow-up. Continued follow-up of infants and further imaging correlation is needed to explore predictors of long-term morbidity.

Increased detection of human parechovirus infection in infants in England during 2016: epidemiology and clinical characteristics

BACKGROUND

Human parechovirus (HPeV), like enteroviruses, usually causes mild self-limiting respiratory and gastrointestinal symptoms. In infants, HPeV can occasionally cause serious illnesses, including sepsis-like syndrome and encephalitis. In summer 2016, Public Health England (PHE) received increasing reports of severe HPeV infections nationally. We, therefore, reviewed all infants with confirmed HPeV across England during 2016.

METHODS

HPeV cases in infants aged <12 months reported to PHE during 2016 were followed up using a clinical questionnaire. Additional cases identified by clinicians completing the questionnaire were also included.

RESULTS

We identified 106 infants with confirmed HPeV infection during 2016. The disease peaked during early summer. Most infants (98/106, 92%) were aged <90 days, and 43% (46/106) were neonates. Fever was the most commonly reported symptom (92%) and signs of circulatory shock were present in 53%. Eighteen infants (18%) required paediatric intensive care admission. Most infants had normal or low C reactive protein concentrations (<10 mg/dL in 75%, <50 mg/dL in 98%). A lumbar puncture was performed in 98% of cases; 92% (33/36) of neonates and 93% (53/57) of older infants had normal white cell count in the cerebrospinal fluid (CSF). Nearly all reported cases (98%) were confirmed by CSF PCR. All infants survived, but five had ongoing seizures after hospital discharge.

CONCLUSIONS

HPeV is an important cause of febrile illness in infants and can have severe clinical presentations. Early diagnosis may help reduce antimicrobial use, unnecessary investigations and prolonged hospitalisation. While prognosis remains favourable, some infants will develop long-term complications-paediatricians should ensure appropriate follow-up after discharge.

Severe Parechovirus 3 Infections in Young Infants-Kansas and Missouri, 2014

BACKGROUND

Infection with parechovirus type 3 (PeV3) can cause severe neurologic and sepsis-like illness in young infants; clinical and epidemiologic descriptions have been limited. We aimed to characterize PeV3 illness and explore risk factors for acquisition in a cluster of neonatal cases at Children's Mercy Hospital in Kansas City, Missouri.

METHODS

Cerebrospinal fluid specimens were obtained from infants aged <180 days who were hospitalized with sepsis-like illness or meningitis between June 1 and November 1, 2014. PeV-positive specimens were sequenced at the Centers for Disease Control and Prevention. We reviewed the medical and birth charts of the infants and performed face-to-face parent interviews. We analyzed characteristics according to infant age and intensive care admission status.

RESULTS

We identified 35 cases of PeV infection in infants aged 5 to 56 days. Seven infants required intensive care (median age, 11 days vs 27 days among those who did not require intensive care; P = .0044). Six of these 7 infants had neurologic manifestations consistent with seizures, and all 6 of them were treated with acyclovir but subsequently tested negative for herpes simplex virus. Virus sequences formed 2 lineages, both of which were associated with severe illness. Half of the infants were reported to have household contacts who were ill during the week before onset. Infants aged ≤7 days at onset were more likely to have been delivered at the same hospital.

CONCLUSIONS

PeV3 can cause severe neurologic illness in neonates, and younger infants are more likely to require intensive care. PeV3 should be considered along with herpes simplex virus and other pathogens when evaluating young infants with sepsis-like illness or meningitis. More widespread testing for PeV3 would enable us to gain a better understanding of the clinical scope and circulation of this virus.

Human parechovirus type 3 infection: An emerging infection in neonates and young infants

Human parechoviruses (HPeVs) are RNA viruses that have characteristics similar to those of enteroviruses and usually cause mild respiratory or gastrointestinal symptoms. Human parechovirus type 3 (HPeV3), first reported in 2004, is exceptional because it can provoke sepsis and meningoencephalitis leading to neurological sequelae, and even death, in neonates and young infants. Pediatricians and researchers are increasingly aware that HPeV3 is responsible for serious disease in neonates and young infants. Retrospective studies and several reports of epidemics of HPeV3 infection have provided data on epidemiology, clinical symptoms and signs, laboratory findings, and outcomes. However, the pathogenesis of HPeV3 infection remains unclear, which explains the lack of specific antiviral therapy and effective prevention measures. Maternal antibodies are important in protection against severe HPeV3-related disease, and this may be a clue regarding its pathogenesis. HPeV3 epidemics are likely to continue, and because the clinical manifestations of HPeV3 are severe, determining the pathogenesis of HPeV3 infection and establishing specific antiviral therapies are important goals for future research.

An outbreak of severe infections among Australian infants caused by a novel recombinant strain of human parechovirus type 3

Human parechovirus types 1–16 (HPeV1–16) are positive strand RNA viruses in the family Picornaviridae. We investigated a 2015 outbreak of HPeV3 causing illness in infants in Victoria, Australia. Virus genome was extracted from clinical material and isolates and sequenced using a combination of next generation and Sanger sequencing. The HPeV3 outbreak genome was 98.7% similar to the HPeV3 Yamagata 2011 lineage for the region encoding the structural proteins up to nucleotide position 3115, but downstream of that the genome varied from known HPeV sequences with a similarity of 85% or less. Analysis indicated that recombination had occurred, may have involved multiple types of HPeV and that the recombination event/s occurred between March 2012 and November 2013. However the origin of the genome downstream of the recombination site is unknown. Overall, the capsid of this virus is highly conserved, but recombination provided a different non-structural protein coding region that may convey an evolutionary advantage. The indication that the capsid encoding region is highly conserved at the amino acid level may be helpful in directing energy towards the development of a preventive vaccine for expecting mothers or antibody treatment of young infants with severe disease.

Parechovirus Encephalitis and Neurodevelopmental Outcomes

OBJECTIVE

We aimed to describe the clinical features and outcome of human parechovirus (HPeV) encephalitis cases identified by the Australian Childhood Encephalitis (ACE) study.

METHODS

Infants with suspected encephalitis were prospectively identified in 5 hospitals through the (ACE) study. Cases of confirmed HPeV infection had comprehensive demographic, clinical, laboratory, imaging, and outcome at discharge data reviewed by an expert panel and were categorized by using predetermined case definitions. Twelve months after discharge, neurodevelopment was assessed by using the Ages and Stages Questionnaire (ASQ).

RESULTS

We identified thirteen cases of suspected encephalitis with HPeV infection between May 2013 and December 2014. Nine infants had confirmed encephalitis; median age was 13 days, including a twin pair. All had HPeV detected in cerebrospinal fluid with absent pleocytosis. Most were girls (7), admitted to ICU (8), and had seizures (8). Many were born preterm (5). Seven patients had white matter diffusion restriction on MRI; 3 with normal cranial ultrasounds. At discharge, 3 of 9 were assessed to have sequelae; however, at 12 months' follow-up, by using the ASQ, 5 of 8 infants showed neurodevelopmental sequelae: 3 severe (2 cerebral palsy, 1 central visual impairment). A further 2 showed concern in gross motor development.

CONCLUSIONS

Children with HPeV encephalitis were predominantly young, female infants with seizures and diffusion restriction on MRI. Cranial ultrasound is inadequately sensitive. HPeV encephalitis is associated with neurodevelopmental sequelae despite reassuring short-term outcomes. Given the absent cerebrospinal fluid pleocytosis and need for specific testing, HPeV could be missed as a cause of neonatal encephalopathy and subsequent cerebral palsy.

Diversity of human parechoviruses in Bulgaria, 2011: Detection of rare genotypes 8 and 10

Human parechovirus (HPeV) infections are commonly asymptomatic but are also found in association with symptoms of the gastrointestinal and respiratory tract, or central nervous system. In order to study their distribution and genetic diversity in Bulgaria, specimens from 229 children aged <5years old hospitalized due to neurological manifestations (n=104) and acute gastroenteritis (n=125) were analyzed. Stool samples were tested using reverse transcription followed by real-time polymerase chain reaction toward the 5'UTR region, and the HPeVs detected were identified by PCR directed to VP1 followed by sequencing. HPeV infection rates of 1.9% and 7.2% were found in children presented with neurological symptoms or with acute diarrhea, respectively. Four different HPeV genotypes, HPeV-3 (n=2), HPeV-5 (n=2), HPeV-8 (n=1) and HPeV-10 (n=1) were identified. All but two HPeVs were detected in acute diarrheal cases, while a single HPeV-3 strain and an HPeV-8 strain were detected in association with facial palsy and encephalitis, respectively. This is the first report of HPeV-8 and HPeV-10 in Europe.