The polio virus has been detected in Melbourne’s sewerage system, prompting health authorities to issue a warning about the importance of vaccinations.
The childhood disease once killed or paralysed thousands of young people each year, but a global effort to eradicate the virus has all but wiped it out.
On Friday, Victoria’s acting chief health officer Dr Brett Sutton announced polio had been detected in tiny concentrations as part of routine testing of pre-treated sewerage at the Western Treatment Plant in Melbourne.
However he said the discovery did not necessarily mean someone had polio.
Dr Sutton said it was more likely that the polio virus came from a person who had received live polio vaccine when travelling or living overseas, and had continued to excrete it since arriving in Victoria.
Oral polio vaccines — administered in some countries — contain a weakened live virus and work by activating the immune response in the body, but have not been used in Australia for more than a decade.
In areas where there is poor sanitation, there is a risk people can acquire polio through the excreted vaccine.
An inactivate polio vaccine is used in Australia, which means it cannot multiply in a person, is not found in the bowel or sewage and cannot cause polio disease.
A health worker gives a polio vaccine to a girl in Lahore, Pakistan, where children continue to be infected. Photo: Muhammad Sajjad/AP
Dr Sutton said there was an extremely low risk that anyone in Victoria would have become infected as a result of the virus detected in sewerage.
“Firstly, polio virus usually doesn’t cause illness even when infection occurs. Secondly, this polio virus was found at concentrations that do not cause infection. Finally, Australia has very high immunisation coverage and excellent sanitation infrastructure that prevents people being exposed to sewage,” Dr Sutton said.
“There are currently no cases of polio in Australia. The last case of polio was in 2007 in a traveller who acquired the infection in Pakistan. Victoria hasn’t had a locally acquired case since the 1970s.”
Worldwide, polio cases have decreased by more than 99 per cent since 1988 – from more than 350,000 to just 37 reported cases in 2016. Countries where the virus persists include Pakistan, Afghanistan and Nigeria.
Some older Australians, aged in their fifties or above, still live with disability as a result of contacting polio as children. Polio survivors are said to be Australia’s largest physical disability group.
The rate of polio vaccination in Victoria is now above 95 per cent for children aged five years or older.
The National Immunisation Program provides a free polio vaccine at two, four and six months of age. A booster dose is provided at 4 years of age.
Also, from July 2017 everyone up to 19 years, refugees and humanitarian entrants have been eligible to receive three doses of polio vaccine as part of catch-up arrangements.
Dr Sutton said this high level of immunisation made any risk of polio occurring in Victoria extremely low, but the positive test was a reminder for people to make sure their immunisations were up to date.
Further information on polio can be found on www.betterhealth.vic.gov.au/health/healthyliving/polio-immunisation