Infectious disease experts warn rates of the human parechoviruses (HPeV) have reached "epidemic" levels in Australia, causing severe complications among babies.

The number of babies suffering severe complications from an emerging infection is on the rise in Australia, infectious disease experts are warning.

Rates of the human parechoviruses (HPeV) have reached "epidemic" levels and infants and children who contract the infection need closer medical attention by doctors and ongoing follow-up, they write in the Medical Journal of Australia.

Most parechovirus infections cause no or mild symptoms, including gastroenteritis or influenza-like illness.

However some HPeV strains such as HPeV3 are associated with more severe infections, including encephalitis and sepsis - blood poisoning.

Children under three-to-six months are particularly vulnerable to HPeV, which has been re-emerging every two years since 2013, according to the MJA paper published on Monday.

Last year more than 200 infants were admitted to hospital as a result of HPeV infection.

"It is now recognised as a leading cause of sepsis-like illness and central nervous system infection, particularly in young infants," wrote the authors, led by Professor Allen Cheng, director of the Infection Prevention and Healthcare Epidemiology Unit at Monash University in Melbourne.

The experts say infants with the serious infection often appear red, hot and "angry".

"HPeV3 disease can be severe with up to 20-50 per cent of admitted patients with sepsis-like illness requiring intensive care admission," the authors wrote.

"Severe manifestations of the acute illness include severe sepsis and meningoencephalitis, which occur in around 10 per cent of hospitalised babies."

There are no effective antiviral therapies for HPeV, and treatment is primarily the management of complications.

Because of this, closer observation by hospital doctors is required to exclude acute complications, the authors advise.

"Hand hygiene, cough etiquette and staying away from child care and school while unwell should be emphasised," the authors wrote.

Follow-up by a pediatrician once the child has recovered is also recommended.

"Because of the evidence of adverse neurodevelopmental outcomes following severe HPeV infection, we recommend that all children hospitalised with HPeV infection should be followed up by a pediatrician at least until school entry, and preferably afterwards, to monitor development and learning, and manage complications including seizures," the authors concluded.