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24 Oct 2020

Identifying a Polio outbreak in Papua New Guinea

Today on World Polio Day, the Doherty Institute reflects on our efforts in responding to a polio outreak in Papua New Guinea.

A World Health Organization (WHO) laboratory based at the Doherty Institute was central to the global public health response during the polio outbreak in Papua New Guinea (PNG).Thanks to the oral polio vaccine, the eradication of poliovirus transmission in all but three countries is one of modern medicine’s greatest success stories.

So when a six-year-old from PNG tested positive to poliovirus in May 2018, there was cause for concern.

The Doherty Institute is home to the WHO Polio Regional Reference Laboratory and also acts as the National Polio Reference Laboratory for PNG. As part of its role, the Laboratory routinely receives stool specimens from cases of polio-like illness (acute flaccid paralysis) in children to monitor the country’s polio-free status.

The lab, run by Associate Professor Bruce Thorley, conducted tests of specimens from community contacts of the positive case in PNG and confirmed it as circulating vaccine-derived poliovirus (cVDPV), which is caused by the virus in the oral polio vaccine.

“The polio vaccine is a weakened form of the virus which induces immunity and should not cause disease,” explains Associate Professor Thorley.

“However, if the vaccine strain replicates in settings with low rates of polio immunisation, it can slowly mutate and then it starts to cause disease.

“Vaccine coverage in PNG has been as low as 40 per cent, while you need more than 90 per cent of the community vaccinated to protect against this happening.”

Following the confirmation, an international public health response ensued to raise the polio vaccine coverage in PNG and to increase surveillance for cases of acute flaccid paralysis.

Over a 15-month period, Associate Professor Thorley and his team tested more than 1300 stool specimens and identified 26 cases of polio due to the outbreak.

At the time of writing, the polio outbreak was expected to be declared over soon.

This article was first published in the Celebrating five years of the Doherty Institute Impact Report.