Poliovirus again identified in PNG

According to health sources in Papua New Guinea, poliovirus type 2 has been detected in the stools of 2 healthy children. The virus was identified during a community screening program in the city of Lae, on the north coast of Papua New Guinea. The same virus has also been found in wastewater samples in Port Moresby.

This poses enormous risk to those in the community who remain unvaccinated. Polio immunization rates are low (< 50%) in some parts of the country. A mass immunization program will target children under 10 years of age.

No cases of clinical polio have been reported to date.

History of polio in PNG and past outbreaks

In 2018 a case of vaccine-associated paralytic polio was first reported in a 6-year-old in Lae. It was the start of an outbreak which resulted in 26 cases of vaccine-associated paralytic polio. Nine provinces reported cases and most (73%) were in children under 5 years of age. A targeted response led to more than 3 million children being vaccinated and an improvement in the polio vaccination coverage to over 97%. The outbreak was quickly contained.

Increased surveillance was recommended in the follow up period but unfortunately the COVID-19 pandemic impacted on many vaccination programs.

Papua New Guinea had been declared free of polio in 2000.

About Poliovirus - Transmission and vulnerability

Polio is a highly infectious viral disease. It is mostly spread through oral contact with faeces (water or objects). The virus is found in the mouth and intestines.

Polio is a disease of poverty and largely affects children under 5 years.

Prior to 1988 there were 3 circulating strains of wild polio virus (wild polio virus type1 (WPV1), wild polio virus type 2 (WPV2) and wild polio virus type 3 (WPV3). Wild polio virus type 2 was declared eradicated in 2015, and wild polio virus type 3 was last reported in Nigeria in 2012 and declared eradicated in 2019.

These successes allowed for the removal of polio type 2 virus from the trivalent Sabin vaccine in 2016.

Vaccine-derived poliovirus and global concerns

Vaccine-derived poliovirus develops from the weakened strain of the live virus found in the polio vaccine. If it is allowed to circulate in unimmunized populations, there is a possibility it can change to a more serious form of the disease and cause clinical paralytic polio (vaccine-associated paralytic polio).

This has occurred in many regions of the world where the oral polio vaccine is being used. As reported, polio returned to Gaza in 2024 - the Gaza war resulted in a fall in immunization rates and provided optimum conditions for an outbreak of polio in the community. Immunisation coverage for the second dose of polio fell from 99% in 2022 to less than 90% in the first quarter of 2024.

It is well recognized that levels above 95% are required to reduce the risk of re-emergence of this old scourge.

The bivalent live oral polio vaccine continues to be used in low-income countries due to its low cost and ease of administration. It is not used in Australia and other high-income countries.

Polio risk to international travellers

The risk of exposure to polio for most travellers is very low. This presumes that most travellers are fully vaccinated. We know that 95% children who are born in Australia receive their childhood vaccinations.

An unvaccinated individual might be protected in Australia but not when travelling. Pakistan and Afghanistan are the only countries reporting the wild polio virus. Risk of the disease mostly applies to countries where vaccine associated polio is being reported. Ninety-two human cases were notified in 2024 and there have been 19 so far in 2025 (May 2025). The Polio Global Eradication Initiative monitors notifications.

Travel advice and booster recommendations

A one-time adult polio booster might be offered to those intending to visit these countries with known outbreaks. This group includes long-term expatriate workers, international volunteers working in NGO’s and those intending basic travel with high-level community exposure.

It is interesting to note that the UK, other European countries and the USA have reported vaccine associated strains in their respective sewage. All countries have excellent public health infrastructure and the risk to the public would be minimal.

The polio vaccine (IPOL) is a safe and effective vaccine. If you undertake frequent travel to low-income countries, then you might choose to have a one-time adult booster. It can also be provided in conjunction with the triple antigen as Boostrix IPV or Adacel Polio in Australia.

Polio eradication still remains a distant dream.

For more on vaccine-derived poliovirus, see our 2024 blog: Polio Eradication Program - Where Do We Stand?