The seven-day moving average of new daily cases has increased from two at the end of January to almost 300 in early April.

This is a dramatic surge, however it is likely these official figures represent the tip of the iceberg, because testing rates are so low.

Since the beginning of the pandemic, PNG has tested people at a rate of just eight people per 1,000, compared with Australia's 624 per 1000 and 48 per 1,000 in neighbouring Indonesia.

Overall, 12% of tests have been positive, far higher than the 5% upper limit that the World Health Organisation uses as a threshold for the quality of a country's testing program.

Given the number of confirmed active cases, and higher diagnosis rates among regularly tested groups like pregnant women and healthcare, NGO and mining workers, it's safe to say at least 80,000 people are currently infected.

Even this could be a significant underestimate, as the low average age of PNG nationals at just 22 likely means high asymptomatic transmission.

Genomic analysis suggests the pandemic has been circulating under the radar for quite some time. Without effective interventions, we expect the number of infections to double weekly and reach one million within weeks.

Governance in PNG is highly decentralised. Health service delivery is devolved to provincial and district health authorities.

This makes the national response to a pandemic challenging. Nevertheless, over the last 12 months, PNG has strengthened its capacity to support a national response.

The National Department of Health has developed a budgeted two-year emergency response plan modelled on a "worst-case" scenario in which one in five of Papua New Guineans is infected with Covid-19.

A National Operation Centre has been activated, along with the UN ‘cluster system’ - a key coordination mechanism for development partners ensuring that responses by international donors, such as Australia, are not an uncoordinated free-for-all.

So far, Australia's support has been generous. We provided $80 million to the global COVAX facility, pledged $523 million to the Regional Vaccine Access and Health Security Initiative and promised $100 million to the so-called Quad initiative undertaken by India, Japan, Australia and the US, which aims to distribute one billion vaccine doses in the Indo-Pacific region by 2022.

Recently, Australia provided 8,840 doses of the AstraZeneca vaccine to PNG's front-line health workers. On 10 April the government announced it will provide 10,000 doses of the same vaccine each week to PNG, Timor-Leste, Solomon Islands and Vanuatu.

Earlier this month, Australia deployed a team of 17 nurses, doctors, and emergency care and infectious disease specialists to assist Port Moresby General Hospital in handling its most urgent cases.

The Australian Council for International Development has found that there is broad support for these measures. Polling conducted by YouGov showed 84% of Australians agree that the government should be supporting PNG to help stop the spread of Covid-19.

The first urgent priority is to provide more assistance to scale up testing across the country. Without accurate and real-time data on rates of new cases, it's impossible to plan when and where to focus containment efforts, including vaccination. This means both test kits and expert technical support are needed.

Second, we need to explore every option to ensure that PNG can vaccinate a high proportion of its population. The promised 10,000 doses per week would take two years to reach one million people with one dose, and that promise is spread across Melanesia.

With ramped-up production of AstraZeneca and decreased demand in Australia, we should be able to provide more doses.

In addition, Australia should proactively reach out to its well-resourced partners in the region, such as Japan, South Korea, Singapore and New Zealand, to form a coordinated alliance of support for PNG.

And then there's China. Since 2016, Australia and China have worked closely with PNG to improve the country's control of malaria.

Building on this partnership, Australia could encourage China to join the alliance and provide expertise and vaccines in a coordinated way rather than pursuing unilateral vaccine diplomacy.

Australia has a moral responsibility to PNG, a country that has been there for us when we needed it most. But it's also very much in our self-interest.

The spread of coronavirus in PNG poses a number of major threats to Australia; both to our health and our economy.

There is tremendous movement of people between PNG and Queensland, representing a significant threat to the Covid-zero status that is allowing Australia to recover socially and economically.

Also, the more the virus spreads, the more likely new variants will emerge that may be resistant to vaccines.

The most important thing Australia can do to safeguard its own vaccine program is to help other countries with large outbreaks get their numbers dramatically down, starting with our closest neighbour.

Professor Brendan Crabb is chief executive of the Burnet Institute and chair of Pacific Friends of Global Health. Professor Mike Toole heads the Centre for International Health at the Burnet Institute