Last week the CDC released an advisory for physicians regarding human parechovirus (PeV) in newborns and infants who have a fever or seizures. This common childhood pathogen typically causes mild illness, but in newborns less than a month old the virus can rarely cause death. The advisory urges clinicians to include PeV in their laboratory workups for children with fever, seizures, or meningitis with no other known cause. Testing is available through state public health or commercial labs. The CDC issued the advisory so clinicians can include PeV in testing to guide treatment and provide answers to parents.
At the moment it is unclear to what degree PeV incidence is higher in the US because the CDC does not routinely conduct surveillance for this virus. The advisory notes that because laboratory testing has become more widely available in recent years, the increased detection of cases could also reflect increased access to lab testing.
What is parechovirus?
Two types of virus — parechoviruses (PeV) and enteroviruses (EV)—can cause various illnesses in children, such as myocarditis, meningitis, and hand, foot and mouth disease. Among the more common EVs is rhinovirus, which causes cold symptoms. PeV and EV are not nationally notifiable diseases but CDC does track these common childhood illnesses through passive reporting. PeV comprises 19 strains, but the most prevalent is PeV-A1, which tends to cause gastrointestinal illness and respiratory symptoms. The strain of PeV currently circulating is PeV-A3, which is known to cause more severe disease.
Can HPeV be serious?
A range of symptoms can present, from none to mild or severe. Children between the ages of 6 months to 5 years typically have an upper respiratory infection, fever or rash. For infants younger than 3 months, and especially newborns less than a month old, infection with PeV-3 can cause serious illness, not always marked by fever. Parents are encouraged to consult their pediatrician when an infant has a fever and is not thriving, experiences loss of appetite, is very fussy or pale. A retrospective study conducted in France to evaluate the severity of meningitis caused by PeV and enterovirus (EV) found that the median hospital stay for infants with PeV was 3 days.
How common is HPeV?
PeV belongs to a group of viruses which are common childhood pathogens and by kindergarten age, most children have been infected with PeV. Two studies in France and Japan among infants younger than 1-3 months having a fever of unknown origin found that approximately 10-20% had PeV.
How long can the virus be transmitted after infection?
According to the CDC advisory, the virus can be transmitted by people with or without symptoms for up to 1-3 weeks. Shedding in the stool may last up to 6 months.
How is PeV transmitted?
Transmission is via fecal-oral route (meaning hand hygiene is important) as well as respiratory secretions. PeV is endemic worldwide with summer and fall seasonality. Although biennial peaks have been noted, other routinely circulating viruses (such as respiratory syncytial virus or RSV) have been off-schedule during the pandemic as people resume normal activities.
Are there any other risk factors?
An interesting Danish study looked the incidence of PeV-3 infections in a cohort of children younger than 5 years. The annual incidence of PeV-3 infection during the period 2009-2012 was 6.6 per 100,000 children. This rate is comparatively rare when considering the highly infectious SARS-CoV-2 Omicron variant which peaked in the US at 860 cases per 100,000 children younger than 5 years per day in January 2022. However, most of these cases were hospitalized, suggesting that many mild infections never came in contact with the medical system. For a more direct comparison, annual Covid-19 or influenza hospitalizations among children 6 months through 4 years have ranged from approximately 40 to 80 per 100,000 over the past two years.
The Danish researchers also looked for any risk factors. Gestational age, birth weight, Apgar score and type of delivery did not appear to increase risk of PeV-3 diagnosis. They found that the incidence of the more serious PeV-3 was concentrated among children younger than 1 year compared to those between ages 1 and 5, PeV-3 was more common among boys, and more common among infants having a slightly older sibling with an age gap of less than 2 years. In fact, the smaller the age gap, the greater the risk of PeV-3 infection.
Although the sample size was small and should be interpreted with caution, the authors speculated that older, first-born siblings could bring home illnesses from childcare which were then spread within the home. An earlier age at first exposure and higher intensity of exposure might explain the severity of illness among the younger sibling.
Taking all this into consideration, a reasonable parent might note that the rate of PeV-3 spread appears low, the virus is common in childhood and circulates seasonally, and most infections are mild. A cautious parent of a newborn might consider increasing hand hygiene for all family members, reducing close-contact exposures with siblings who are sick, and staying current on newborn vaccinations to prevent severe outcomes due to other illnesses. This will make it easier for the pediatrician to troubleshoot symptoms and order the right tests. When caring for infants and young children, soap and water is the preferred method of handwashing because non-enveloped viruses may be less susceptible to disinfection with hand sanitizer. Finally, encourage visiting friends and family to use good hand hygiene and common sense about holding and kissing the newborn if feeling unwell.