Human parechovirus type 3 in Victoria

What is the issue?

Human parechovirus (HPeV) belongs to the Picornaviridae family of viruses. HPeV types 3, 6 and 1 are commonly associated with disease. A recent increase of HPeV type 3 has been detected in Victoria. Twenty-two cases have been identified since May 2022. All cases have been in infants. Epidemics of HPeV causing disease in young children have been identified every two to three years in Australia since 2013.

Most infections caused by HPeV are mild or asymptomatic, however severe disease manifests as neonatal sepsis-like syndromes and meningitis. HPeV type 3 has caused severe disease in infants and neonates during previous outbreaks.

HPeV are closely related to enteroviruses but are not detectable in standard enterovirus polymerase chain reaction (PCR) tests. For this reason, specific parechovirus testing needs to be undertaken.

Human parechovirus infection is not a notifiable condition in Victoria.

Who is at risk?

HPeV infection occurs commonly in the general population. Children are more likely to develop symptoms, and neonates and young infants are at risk of more severe disease.

Consider HPeV as a differential diagnosis, and request specific parechovirus PCR, in neonates and young infants presenting with meningoencephalitis or a sepsis-like syndrome.

Symptoms and transmission

Most people infected with HPeV experience no symptoms. Some people may develop a mild gastrointestinal or respiratory illness characterised by diarrhoea, cold and flu-like symptoms, and fever.

Some strains of HPeV, including type 3, can lead to more severe disease such as sepsis-like syndrome, meningitis, encephalitis, flaccid paralysis, seizures, and hepatitis. Infants, particularly under the age of 3 months, are more likely to develop severe disease. They may become unwell very quickly and present with fever, irritability, tachycardia, pain, drowsiness, lethargy, and an erythematous skin rash.

HPeV is usually spread from person to person through contact with respiratory droplets, saliva or faeces from an infected person. It can also be spread through objects and surfaces that have been contaminated with infected secretions.

Recommendations

HPeV is not detected by standard enterovirus polymerase chain reaction (PCR) tests used at most pathology services. In addition, cerebrospinal fluid (CSF) may not display pleocytosis (an increase in lymphocytes) in HPeV infection. Therefore, the diagnosis of HPeV infection should be considered in neonates and young infants with a clinically compatible illness, and parechovirus PCR should be specifically requested. This may be available locally in a limited number of laboratories. If not, the testing may be accessed through VIDRL.

VIDRL tests for HPeV whenever enterovirus testing is requested (dual testing) and can be performed on stool specimens, nasopharyngeal aspirates or throat swabs, CSF, or whole blood samples (collected in an EDTA tube). Stool and CSF are the preferred samples.

For CSF samples in infants less than six months of age where enterovirus PCR has been requested, laboratories should consider automatically sending to VIDRL for HPeV testing.

There is no specific treatment available for HPeV. Treatment is aimed at supportive care and symptom relief. Severely unwell cases need to be assessed and treated for suspected sepsis under the care of an emergency consultant or paediatrician.

Prevention

Prevention of human parechovirus infection is the same as for viral gastrointestinal illnesses. Hand hygiene is important. In hospitals, contact and respiratory droplet precautions are recommended

For the public, good hygiene is the best protection. This includes hand washing, cough etiquette, cleaning of soiled clothing and surfaces, and social distancing when unwell.

There is no vaccine to protect against HPeV infection.