Papua New Guinea's polio outbreak explained and whether it could spread to Australia

Australia Broadcast Center

15-05-2025

Two cases of poliovirus type 2 have been detected in children who live just over 500 kilometres north-east of Queensland's Cape York, and a "national emergency response" has been triggered by Australia's closest international neighbour.
The World Health Organization (WHO) confirmed on Thursday that polio was detected in Papua New Guinea (PNG) from a wastewater sample in the city of Lae and an environmental sample in the nation's capital, Port Moresby.
Further testing by the WHO, PNG Department of Health, UNICEF and local provincial health authorities then confirmed the virus in the two healthy children in Lae, and genetic sequencing showed the strain was linked to polio circulating in Indonesia.
The WHO says wild poliovirus type 2 was eradicated in 1999 and type 3 was wiped out in 2020. As of 2022, there were just two countries still impacted by wild poliovirus type 1 — Pakistan and Afghanistan.
So, how in 2025 is the virus still being detected in some of Australia's closest neighbouring nations and what is the risk of it spreading here?
The WHO describes polio, also known as poliomyelitis, as "a highly infectious viral disease that largely affects children under 5 years of age". There is no cure and can only be prevented through vaccines.
The organisation says it can be spread person-to-person, mostly through inadvertent consumption of infected faecal matter, but it can also be transmitted through contaminated water or food.
The Australian Department of Health says polio is "a serious disease that can lead to long-term disability, paralysis and death".
The federal department also says most people who are infected by polio recover completely, "but a small number experience muscle and nerve damage that result in lifelong disability."
Australia's virtual public health information service, Healthdirect, says that 95 per cent of people who are infected by poliovirus experience no symptoms, despite the virus being able to incubate for up to 35 days.
Other patients develop flu-like symptoms, like a fever, fatigue, nausea, vomiting, a sore throat, weak muscles and a headache for as long as 10 days from the point of infection, according to Healthdirect.
For less than one in every 100 infected people, symptoms can also include severe muscle weakness known as acute flaccid paralysis that typically impacts a person's limbs. The virus can be fatal if it impacts the diaphragm and a person's breathing.
For almost 40 years, the world has been fighting to keep levels of polio as close to zero as possible.
In 1988, the WHO assembly resolved to eradicate the virus internationally with a "Global Polio Eradication Initiative", supported by national governments and global disease prevention groups.
Since then, the organisation says that cases worldwide have dropped by 99 per cent and across the three strains of the virus, type 2 has been officially eradicated for 26 years and type 3 for five years.
The Australian government says the country has been polio-free since 2000, and in 2022 the National Centre for Immunisation Research and Surveillance (NCIRS) said that 93.9 per cent of children aged one were considered immunised after receiving three doses of the polio vaccine.
The government's current data shows that while that figure has reduced slightly for one--year-old babies, more than 95 per cent of two-year-old children and almost 94 per cent of three-year-old children are immunised.
Australia also has its own polio surveillance program, which the government says is publicly-funded "to prevent, prepare for, monitor and respond to the threat" both domestically and abroad.
That program works to detect cases of polio that may have been imported into Australia from other countries, and to mitigate local transmission while also engaging with the WHO.
In PNG, the WHO says that polio was wiped out in 2000 but the country has been susceptible to cases due to low immunisation rates and "suboptimal" surveillance.
The country experienced a small polio outbreak in 2018 but it was brought under control the same year and there have been no detected cases until now.
Further abroad, there are just two countries that the WHO says continue to be impacted by endemic polio — Afghanistan and Pakistan. A nation is considered endemic when there is transmission of wild strains of the virus.
Another 20 countries are considered to be polio-free, however, the WHO had not certified that data by 2023, and there are 173 nations confirmed to have eradicated the virus.
Notes distributed by the WHO's representative in PNG, Dr Sevil Huseynova, on Thursday suggested that the latest polio outbreak in the country can be attributed low vaccine rates and the virus's transmissibility.
"As these challenges significantly increase, the risk of vaccine-preventable disease outbreaks and hinder our ability to detect and respond to cases promptly.
"Polio is a highly infectious disease, and in communities with low polio immunisation rates, the virus quickly spreads from one person to another."
The WHO and UNICEF have also quickly mobilised to respond to the outbreak with widespread surveillance of any cases of acute flaccid paralysis, a three-stage immunisation program aimed at protecting children and boosting the nation's vaccine rates to prevent further spread.
Linda Selvey, an honorary associate professor at the University of Queensland's School of Public Health, told ABC radio's PM program on Thursday that the risk of polio spreading to Australia "would be fairly low".
Australia has not had a major outbreak of polio since 1961, and Australian children are now vaccinated against the virus as part of their routine immunisation as infants.
Dr Selvey has worked on polio eradication programs in the past in India and Nepal and said that for PNG, the impact of the virus's spread could be dire.
"I'm concerned about the outbreak from the perspective of the people in Papua New Guinea in particular because they generally have very low immunisation coverage," she said.
"While they haven't actually had a clinical case of polio, it would be quite possible.
"The other thing is because health services are not great in many parts of PNG, a child might get polio without it being detected, so then that means there's a chance of surface spread."
Despite that risk and the WHO saying on Thursday that "polio anywhere is a threat everywhere", Dr Selvey says Australia's immunisation rates provide the country with a high level of protection.
"We're only at risk if we have a population who's not immune. Generally, I think our immunisation coverage in Australia is still pretty good, even though it has fallen in the last few years," she said.
"We also have very good sanitation and so-on, we don't generally live in particularly crowded areas. I would think that the risk would be fairly low.
"The greatest risk would be in the parts of Queensland, in particular in the Torres Strait, where there's closer movement of people between Papua New Guinea and Australia and also where the housing and so on is less optimal."
In interim 2024 youth vaccination figures released by the NCIRS on Thursday, childhood immunisation rates were shown to have continued declining since the COVID-19 pandemic.
The data showed that last year 91.6 per cent of one-year-old babies were considered fully vaccinated, down from 94.8 per cent in 2020.
For children aged two, the rate was 89.4 per cent in 2024, down from 92 per cent four years prior, and it had dropped from 94.8 per cent in 2020 to 92.7 per cent last year for five-year-old children.
Complete childhood vaccination includes immunisations for diseases like Hepatitis B, Diptheria, Rotavirus, Meningococcal B, Influenza and polio by the age of five, according to the National Immunisation Program Schedule.
The Department of Foreign Affairs and Trade (DFAT) said in a statement on Thursday that Australia is working to support the immediate immunisation response in PNG.
"Australia is working closely with Papua New Guinea, the World Health Organization and UNICEF to help respond to the detection of vaccine-derived poliovirus," a DFAT spokesperson said.
"We're supporting PNG's National Polio Response Plan, including through targeted technical assistance."