Watch Professor Catherine Bennett explain the differences between a pandemic and an endemic virus

The world is now entering the third year of the COVID-19 pandemic, but the way the virus is being spoken of has gradually shifted.

In September 2021, Health Minister Greg Hunt heralded a new era of the virus, announcing in a press conference that it was "clear that the pandemic is endemic".

But what does it mean for a pandemic to turn endemic? Does that mean the virus will be less lethal around the world?

To find out what an endemic COVID-19 might look like, Australian Community Media put questions to Professor Catherine Bennett, chairperson for epidemiology at Deakin University in Victoria.

According to the Royal Australian College of General Practitioners' definition, an 'outbreak' is a sudden rise in disease cases over a short period of time in a specific place. For example, a cruise ship might have an outbreak of salmonella contamination.

It is relatively contained from the general population, but it might be uncontained in a certain place over a certain time, among a certain population group (i.e., the staff and passengers of the cruise ship).

An epidemic is a step above an outbreak that affects a certain geographic area. For example, the Ebola virus which spread through West Africa between 2014 and 2016.

A virus becomes an epidemic when it starts to affect multiple countries, and it becomes a pandemic when it is no longer contained to continents.

For example, the Spanish Flu of 1918, the HIV/AIDS, SARS-CoV-1 and the Zika viru have all at some point been considered epidemics or pandemics.

When it becomes a recognised circulating virus in any specific place over any amount of time, the virus is said to become endemic.

Ross River Fever is an example of an endemic disease because it circulates in Australia and the Pacific Islands, but is relatively unfound in the rest of the world.

Rhinoviruses that cause the common cold also circulate seasonally around the world, so influenza is another example of of an endemic virus.

It's something that can be monitored and measured, and at times might cross over into the pandemic category again.

"It means that this is a virus that we know is circulating in the community and that like the flu, you might have waves," Professor Bennett said.

"Every infection initially was unexpected because it wasn't a virus that we'd seen as a human pathogen before.

"So this is now acknowledging that the virus won't be eliminated in the short term. It will still continue to circulate and we might see some waves continue, maybe more seasonal, but still maybe as we've seen in Australia, new waves that can occur at any time."

When a virus becomes endemic, it may still cross over into pandemic categorisation again, as Professor Bennett explains.

"So it can actually like the flu cause severe illness in certain situations, and you might, like the flu actually transition from seasonal or endemic to something that becomes pandemic again," she said.

"It doesn't mean it's in that endemic state for ever. We're now at risk because we have another corona virus that we need to worry about as a human pathogen.

"But it's putting those things in place that allow us to manage this in a more sustained way and to take advantage of the protection against severe illness that both prior infection and vaccination now is helping to bring to the world community."

High levels of infection around the world could, unfortunately, still equal a high death toll, even once the COVID-19 pandemic has become an endemic virus.

"Other endemic diseases include HIV AIDS and malaria, for example," Professor Bennett said.

These viruses are still responsible for enormous cases of severe illness and death around the world each year.

Professor Bennett expects that an endemic world will have far less restrictions in place.

"If we possibly can I think what we'll see is an easing up of the controls," she said.

"You know, we talk about levers. We've got the vaccination as one important lever. We've also got past infection is another important lever that actually allows us to tolerate the virus in the community in different ways without quite the same impact at the hospital end of things."

NSW, Victoria, and ACT have this week eased restrictions when it comes to masks and check-in requirements, and this Professor Bennett said, will become more of the norm.

No longer will things like masks be mandated even if it continues to be encouraged in certain settings.

"We know what works in our communities. We know that wearing masks, particularly if you're a highly vulnerable and wearing a good mask, like an N95 mask, that can actually help protect people," Professor Bennett said.

"So I think those things will ease back when infection rates are low in the community as we come out of these waves.

"But if we start to see cases on the rise as we go into winter or a new variant starting to appear in larger numbers, then these are the things that would be done."

Into the future, Professor Bennett expects, there will be more emphasis on protecting vulnerable communities without strictly restricting the general population.

"We might have, you know, schools no longer doing screening after the first few weeks of semester. But that might come back in if we start to see infection rates in the local community rise so that they then want to make sure that they reduce the risk of infection happening within schools," Professor Bennett said.

"Some countries now easing back. They might need to dial those up again going ahead. But I think the days of full border closure or widespread interventions are gone.

"We can protect the people who are the most vulnerable, but we can also get on with normal day to day activities working around, face these requests from time to time that might happen."

The emergence of the Omicron variant may have accelerated the world's progression from pandemic to endemic.

"It's reasonable that it could happen over this year," Professor Bennett said.

"[Omicron] pushed up the level of people in the community that do have a level of immune protection based on prior infection as well [as through vaccination].

"It also forced us to be more pragmatic about the way we tested for cases and the way we managed infections in the community.

"We've pulled back our efforts to find as many cases as we can, or close all our borders to keep cases from coming in, [instead] it's about knowing enough about what's going on in the community that we know where the virus is, what impact it's having on the community and where we're vulnerable."