The World Health Organization (WHO) has expressed deep concern and says neighbouring countries are at risk as it declares an outbreak of polio virus in Papua New Guinea.
Community transmission of the virus was confirmed in the city of Lae, after a screening program detected the fast-spreading virus in stool samples from two healthy children.
Poliovirus Type 2 has also been found in environmental samples in the capital Port Moresby.
WHO representative in PNG, Dr Sevil Huseynova, said the outbreak posed a serious risk to young children in PNG, where less than 50 per cent of the population immunised against the disease.
"In communities with low polio immunisation rates, the virus quickly spreads from one person to another," she said.
Polio is a highly infectious viral disease that mainly affects children under the age of five.
The virus is transmitted through the faeces and saliva of an infected person — often passed on via contaminated hands, food, or water — before it makes its way into somebody's gut.
Most people infected with polio show no symptoms; the ones that do generally get a flu-like illness.
But in rare cases, the virus invades the nervous system, leaving one in 200 people with irreversible paralysis.
'Polio anywhere is a threat everywhere'
PNG 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.
The WHO said the recently detected virus was genetically linked to strains circulating in Indonesia, which shares a land border with PNG.
Dr Huseynova said because the virus spreads rapidly, it also posed a risk to other nations.
"Polio anywhere is a threat everywhere, especially to our children. Polio in Papua New Guinea can spread to neighbouring countries and anywhere in the world," Dr Huseynova said.
The PNG Department of Health has launched a rapid response program with assistance from the WHO, UNICEF and the Australian government.
It will focus on vaccinating people, especially children under five years of age, in target areas, along with monitoring and surveillance.
PNG Health Minister Elias Kapavore said the outbreak was likely due to low immunisation rates.
"WHO requires us to have immunisation coverage of above 80 per cent at the moment, unfortunately our coverage is below 50 per cent and that has been a huge concern to us," he said.
"Many of our parents do not take that responsibility to bring their children or babies to be immunised."
He said no clinical cases had been detected at this stage and the two children who were exposed to the virus were vaccinated and therefore did not become infected or symptomatic.
The mass immunisation program will target around 3.5 million vaccinated and unvaccinated children between the ages of 0 and 10.
In Australia, a Department of Foreign Affairs and Trade spokesperson said the federal government was supporting PNG's response to the outbreak with "targeted technical assistance".
"Australia is working closely with Papua New Guinea, the World Health Organization and UNICEF to help respond to the detection of vaccine-derived poliovirus," the spokesperson said in a statement.
"Australia is proud to be PNG's partner of choice and we will continue to work with PNG to support the health and development of its people, and to ensure a healthy region."
UNICEF PNG country representative Veera Mendonca said she was confident the outbreak could be contained with a rapid action plan.
"If you're immunised and you have the virus, it has no effect on you … if you're immunised, no problem. This is why it is important for every child to be immunised," she said.
She commended the PNG government for its efforts in improving vaccine coverage in the country prior to the outbreak by ensuring stocks and cold chains in remote areas.
"In the country we have areas with only eight per cent coverage. But we also have 82 per cent coverage — so we know it is possible," Ms Mendonca said.
