Poliovirus has been detected in a sample of Perth’s wastewater, health officials have revealed.
Authorities said the detection in mid-April was evidence of a vaccine-derived poliovirus Type 2 strain, similar to what has been identified in countries such as Africa, Europe and Papua New Guinea in recent years.
Western Australia’s chief health officer, Dr Clare Huppatz, said while it was extremely unusual, it presented a very low risk to the population.
“While this is a significant finding, this detection does not provide evidence of spread of the disease in WA,” she said.
“The potential for this strain to circulate in a highly vaccinated population is very low, and the poliovirus vaccination coverage in WA children is 92 per cent.”
Dr Huppatz noted the presence of the virus in wastewater in Europe during 2024 and 2025 did not lead to anyone developing the disease.
What is vaccine-derived poliovirus?
The vaccine for poliovirus effectively interrupts person-to-person spread.
But on rare occasions in under-immunised populations, the live weakened virus contained in the vaccine can mutate and circulate, according to the Global Polio Eradication Initiative.
That results in vaccine-derived poliovirus, as suspected in this case.
Australia uses inactivated polio vaccines which do not contain live virus and are given by injection.
“This finding is most likely from someone who has travelled overseas and is shedding this virus strain,” she said.
But she said the case served as a reminder for people to be fully vaccinated against the disease while it still circulated overseas.
“The best thing they can do is check that they’re vaccinated … I wouldn’t expect to see this be a risk to the community, it’s just something that we really do need to monitor,” Dr Huppatz said.
University of New South Wales medical epidemiologist Dr Abrar Chughtai said there had been similar detections in Australia recently.Â
“Australia previously detected vaccine-derived poliovirus in Melbourne wastewater in 2024, linked to an unvaccinated traveller,” he said.Â
“Similar detections have occurred globally in many countries … mainly in under-immunised populations, with no subsequent outbreaks.”
Testing increased​
The WA Department of Health said it was now increasing the frequency of wastewater poliovirus testing in the Perth metropolitan area.
Dr Huppatz said the virus was detected in the Subiaco wastewater treatment plant which covers Subiaco and the Perth CBD, an area of about 250,000 people.
Dr Clare Huppatz says wastewater testing for poliovirus will be done weekly in the near future. (ABC News: Hugh Sando)
She said people “can actually excrete the virus for quite some time”.
“We will continue to test the wastewater in the Subiaco treatment plant but also in the adjacent ones, which cover a lot of the population of Perth,” she said.
“We’ll test weekly for the next few months to test what the signal shows.
“We will also alert any clinicians to look for any clinical cases, as part of our surveillance.”
History of polio in Australia
According to the Australian Institute of Health and Welfare (AIHW), Australia was declared polio-free in 2000.
A chart has shown a sharp decline in polio cases since 1956, when the vaccine was introduced in Australia. (Supplied: Australia Institute of Health and Welfare)
“Although there has been no known local transmission of the poliovirus in Australia since 1972, there remains a risk of the importation of polio from overseas,” its website reads.
Since 1987, the only case of polio detected in Australia was in 2007 when an overseas-born student acquired the disease during a visit to a country with known ongoing polio transmission, according to the AIHW.
The previous two epidemics of polio in Australia were in 1956, and from 1960 to 1962.
Cases of polio sharply declined after 1956, when the vaccine was introduced.
Polio, also known as poliomyelitis, is a highly contagious viral infection caused by the poliovirus.
Polio spreads through contact with infected faeces, leading to gastrointestinal infection.
According to the World Health Organisation (WHO), polio can spread through contaminated water or food, and largely affects children under 5 years of age — although anyone of any age who is unvaccinated can contract the disease.
‘Wild’ poliovirus cases have decreased by over 99 per cent since 1988, the WHO said, but the virus is still endemic in two countries — Pakistan and Afghanistan.