The same virus, a strain of enterovirus 71 (EV71), has led to hundreds of deaths in China.
Five children, including one in Victoria, have suffered from a polio-like paralysis this year because of a severe complication from the strain, known as C4a.
Dr Bruce Thorley, of the Victorian Infectious Diseases Reference Laboratory, said the C4a strain had been circulating in Asia for some time but was only now being detected in Australia.
GOING VIRAL The trail of EV71
1969 Enterovirus 71 (EV71) is isolated by scientists in the US
1972 First recorded outbreak in Melbourne: 39 cases with nervous system complications
1986 Melbourne and Sydney struck by 33 severe cases
1999 Perth: 14 cases reported, 4 with permanent disability
2000 Sydney: 9 cases with nervous system complications, including 5 patients with fluid on the lungs
2013 NSW and Vic: 5 cases of polio-like paralysis, with 27 severe cases reported in NSW in month to May 12
Source: NSW and Vic health depts; WHO
Strains of EV71 that usually circulate here cause milder symptoms such as rashes, fever and blisters on the hands, feet and mouth (commonly known as hand-foot-and-mouth disease, or HFMD).
But the C4a strain could, in rare cases, cause more severe neurological complications such as inflammation of the brain — meningitis and encephalitis — and paralysis, according to Dr Thorley.
In NSW, 27 children who were admitted to hospital with meningitis or encephalitis in the month to May 12 had an EV71 infection.
Dr Thorley cautioned that strains of EV71 were often circulating among the population and most infections did not cause any noticeable symptoms in adults or children.
“But now, to have such a number of positive detections including paralysis, I would regard it as an outbreak,” he said.
He said four of the cases of paralysis were in NSW and one in Victoria, with investigation of all cases of paralysis in children being coordinated in collaboration with the Australian Paediatric Surveillance Unit.
Victoria’s Chief Health Officer, Dr Rosemary Lester, said there were a few more severe cases than normal caused by EV71 infections in Victoria. As a result, the State Government had asked hospitals and laboratories to alert health officials to any cases.
She said the Government did not have enough information to suggest Victoria was faced with an outbreak of EV71 infections.
“For Victoria, it certainly doesn’t look like the situation is as bad as NSW,” she said. “Having said that, we’re obviously trying to gather more information.”
The original source of the C4a strain was likely to have been travellers and visitors from infected areas, but it would now be established in the community, according to Dr Thorley.
He said EV71 was related to poliovirus but there were no specific antiviral treatments or vaccines for fighting it, although a potential vaccine is currently being trialled in China. Young children are more susceptible to developing severe complications.
According to a NSW Government health alert, nervous system complications from EV71 can lead to irritability, seizures, unsteadiness and weakness. In extreme cases, it can lead to permanent effects.
Dr Lester said parents and children should use standard good hygiene precautions such as hand-washing with soap and water to help limit the spread of the virus.
After an EV71 outbreak in Western Australia in 1999, a study in the medical journal Clinical Infectious Diseases found that of the 14 children with severe complications, four had permanent damage to the nervous system, with one child becoming a quadriplegic requiring breathing support.
Dr Thorley said HFMD was usually a mild condition caused by the coxsackievirus A6 or A16, but the rare and more serious cases were usually associated with EV71.
According to a World Health Organisation (WHO) report, “A Guide to Clinical Management and Public Health Response for Hand, Foot and Mouth Disease”, EV71 is a growing problem in our region.
The WHO noted that in China in 2009, more than one million HFMD cases were notified to authorities. Of those analysed, 81 per cent of the 13,810 severe cases and 93 per cent of the 353 deaths were caused by EV71.
Dr Thorley said in response to growing concern, the Enterovirus Reference Laboratory Network began surveillance of EV71 in 2009. Samples from children under 15 years with polio-like paralysis are now routinely tested for both poliovirus and EV71.
Scientists in China have been working on a vaccine for EV71 and this week published a study in The Lancet showing advanced trials of a vaccine against the C4 strain that predominates in China.
Dr Nigel Crawford, of Melbourne’s Royal Children’s Hospital, told the journal that an important next step would be to test whether the vaccine could protect against other strains of EV71.