Nestled in Papua New Guinea's remote highlands region, the Mount Hagen Hospital has about 250 beds and services about half a million people.

As a result, the hospital usually functions at or above capacity, and that's outside of a pandemic.

So, when COVID-19 cases began to surge this year, the hospital was put under even more strain. It escalated further when staff themselves soon became infected.

"We've had about 110 staff who have been infected, or are currently, with COVID. And yes, when you have a limited pool, that does mean that you need to redirect services," manager of the Mt Hagen Hospital and acting chief executive of the Provincial Health Authority, Jane Holden, said.

But after a "major rise" in March and April, the region has seen a recent fall in cases.

Its 18-bed COVID ward, which was reserved for seriously ill patients and had been at capacity last month, now has only four patients.

Why have cases dropped?

The Western Highlands region was identified early on as a hotspot, and a team of international health workers was sent to assist local staff.

While cases have surged during the last two months, health workers in PNG say there has been a decrease in cases in recent weeks. They are still trying to figure out why.

Health workers are looking at the broader trends, lower hospitalisation numbers and a slight decrease in the test positive rate, which is a measure of the percentage of people testing positive.

But problems with data collection is making it difficult to assess what exactly is happening. And there are warnings that the "true extent" of the decreasing trend must be interpreted "with caution" because of issues that have been identified with data collection.

Only half of the COVID-19 cases recorded in the Western Highlands Province appear in the national statistics.

When contacted by the ABC, the Western Highlands Provincial Health Authority said it had recorded 1,135 cases since the pandemic began. Yet on the same day, the national statistics said it had 538 cases.

The hospital said it had recorded 19 COVID-19 deaths, but only eight were listed in the national data.

PNG is still struggling with low testing numbers, with just over 100,000 tests conducted in the country since March last year.

It's being put down to shortages of testing supplies, long turnaround times for results and reluctance from some people to be tested because of stigma surrounding the virus.

Ms Holden said the discrepancy between the figures recorded at a local and national level was a concern.

Several provincial health authorities have raised the same issue, with each province responsible for collecting its own case numbers and submitting them to the national COVID-19 control centre.