Outbreak of polio announced in Papua New Guinea — and what New Zealand can do
27 May, 2025
Interview by Joel Armstrong, adapted by Leilani Cardosa
The World Health Organisation (WHO) recently announced an outbreak of Circulating vaccine-derived poliovirus type 2 (cVDPV2) in two healthy children in Papua New Guinea.
This follows a similar outbreak in 2018 in the country, which was controlled within a year.
This strain originates from the oral polio vaccine (OPV), which contains a live, weakened form of poliovirus. The vaccine briefly replicates in the intestine and therefore creates immunity by building up antibodies.
However, in rare cases, this vaccine strain can mutate as it replicates in the gut. In under-immunised communities, these mutated viruses can spread and evolve further. The lower the population’s immunity is, the longer vaccine-derived polio can survive and undergo more genetic change.
Poliovirus, a species of Enterovirus, spreads primarily through the faecal-oral route, via contaminated water, food, or poor hygiene.
While 75-90% of infections can be asymptomatic, about 1% lead to meningitis, and 0.1% can cause myelitis. Myelitis primarily affects children, resulting in muscle weakness due to inflammation and nerve damage to the spinal cord.
The current outbreak was identified through ongoing wastewater surveillance. Scientists found poliovirus in sewage samples from Port Moresby and Lae, leading to stool testing in nearby communities. The virus was detected in the stool samples of two healthy children from different villages.
Associate Professor of Infectious Diseases at the University of Auckland, Mark Thomas, told 95bFM’s The Wire that these cases likely point to broader community transmission.
“Those children were perfectly well… That suggests to me that the virus is widespread in those cities in Papua New Guinea, for them to find it in the wastewater and then in the poo of the children.”
With only 47% of Papua New Guinea’s population fully vaccinated against polio, public health officials face a significant challenge in further preventing the spread of the virus.
Thomas says part of the reason for low vaccination rates is an underdeveloped health system.
In response to the new outbreak, Papua New Guinea’s Health Minister, Elias Kabavore, has pledged to vaccinate 100% of the population by the end of the year.
While Thomas acknowledged the importance of high vaccination rates, he is unsure about how feasible achieving full coverage is, especially considering Aotearoa’s vaccination rates.
“We don't achieve 100% in New Zealand … we're at about 90% across the whole country. We're at much lower rates in some groups in the community.”
Thomas says New Zealand could support Papua New Guinea through targeted assistance; both in resources and skilled personnel.
Looking ahead, he stresses long-term progress would depend on broader improvements to infrastructure and living conditions.
“I think improving the wealth of the country would be a good start, and then having the resources to reach widespread [use] through the community and probably providing a very expensive thing, but providing sewage and clean water would be probably a very good start.”
