Explainer: what is the new enterovirus or EV71?

The new strain (C4a) of enterovirus EV71 has infected hundreds of thousands mostly pre-school-age children in China, Cambodia and Taiwan. Image from shutterstock.com

A virus that can cause paralysis in children has been circulating in New South Wales during autumn and has recently spread to Victoria.

Around 30 young children, mainly from Sydney’s northern and southeastern suburbs, were admitted to hospital with neurological complications last month. Five cases of EV71 paralysis were reported in New South Wales and Victoria in early June.

The cause is a new strain (C4a) of enterovirus EV71 which has infected hundreds of thousands of mostly pre-school-age children in China, Cambodia, and Taiwan in recent years.

While the paralysis caused by EV71 can in some ways be compared to that caused by poliovirus, the two viruses are not related. Polio has been eradicated from Australia by immunisation; the last cases of polio in Australian children was around 40 years ago.

Symptoms

Outbreaks from different strains of EV71 occur regularly in Australia and normally cause a mild illness in children. The most common of these illnesses is hand, foot, and mouth disease (not to be confused with the foot and mouth disease that affects animals).

Children with hand foot and mouth disease develop a fever and rash, and blisters localised to the foot, hand, and throat. It’s important to let the blisters to try out naturally, rather than burst, as the fluid within them is infectious. The incubation period for the disease is three to five days, and the illness lasts around five days.

Hand, foot and mouth disease causes localised blisters. Flickr/Marc van der Chijs

But some strains of EV71, such as C4a, can cause much more serious illness. In some cases, the virus causes inflammation of the brain and spinal cord. The heart and lungs may also be affected, leading to life-threatening encephalitis or heart failure.

Large C4a outbreaks have occurred in different parts of east Asia for the last four to five years, and it seems that this strain has now reached Australia.

Most cases initially develop fever and a rash. More serious signs are sudden weakness in the limbs, excessive drowsiness or irritability, or evidence of heart and lung inflammation, such as being out of breath.

How does the virus spread?

Like many viruses, EV71 is transmitted by faecal contact and by coughs and sneezes (droplet infection). Spread from respiratory droplets can be limited by use of tissues and avoiding contact with others.

Careful hand hygiene is important. Parents toileting children or changing nappies should be particularly careful to routinely wash their hands with soap and to use disinfectants where needed.

Isolation of cases is very effective at limiting spread, and children with hand, foot and mouth disease should be kept at home until the blisters have cleared up.

Treatment

There is as yet no vaccine or curative treatment available on the market, but the Chinese company Sinovac has successfully tested a vaccine against EV71 in children. The trial, involving 10,000 children, showed a much lower incidence of hand, foot and mouth disease among the immunised children. Sinovac has applied for permission to market the vaccine.

Treatment with certain antiviral agents is being considered in China, but these studies are at a very early stage.