Covid 19 Omicron outbreak: Virologist answers five questions about winter

We're in the thick of an Omicron wave right now – but what can we expect when other, more familiar viruses return to a reopened New Zealand? Otago University virologist Dr Jemma Geoghegan answers five questions.

What trends are you expecting to see this winter?

It's hard to say yet - but there are clues in last winter.

When we opened a travel bubble with Australia, we experienced a very large and severe wave of respiratory syncytial virus, or RSV, which is highly contagious and causes lung and respiratory tract infections.

There were more than 6000 cases RSV cases reported here, but the true size of the outbreak was likely much bigger because of under-reporting.

And it was most likely large and severe because we had an immunonaïve population – or that we hadn't been exposed to the virus for a year, because our borders were closed.

Whether we get it as severely as that again, we don't know.

Otago University virologist Dr Jemma Geoghegan says our hospitals will be busy this winter, no matter what winter ills are circulating. Photo / Supplied

But it gives us some idea of what might come as our borders gradually open up, and not just with RSV, but other viruses like influenza, human metapneumovirus (HPV), enterovirus and adenovirus.

There's a risk diseases like measles might come back, because, having had other priorities, our vaccine rates for them aren't as high as we'd like them to be.

There are also those viruses that just cause common colds, like rhinovirus. Because we don't actively survey them, we can't say we've necessarily eliminated them – although there may be some that we have.

Latest week of FluTracking data is up on our little Shiny app 🧵 to follow, but tl;dr highest levels of Influenza-like Illness since winter flu season 2019 https://t.co/NLV5YY3N82 pic.twitter.com/FCPIsRiJfA

— Emily Harvey (@emilynz) March 3, 2022

We know that winter also traditionally comes with a higher risk anyway, because people's behaviour changes. We're more likely to be indoors and not have windows open.

That said, reintroduction of viruses can cause outbreaks outside of winter too – just as we saw with RSV when it took off in Australia over summer before it came here last year.

So, every new reintroduction of these viruses has the potential to cause problems here.

What can we say about the risk of flu season, particularly?

Influenza is going to be interesting to observe.

Traditionally, around 200,000 New Zealanders catch it each year, we often get seasonal surges in hospitals, and an estimated at least 500 people die from it.

Non-pharmaceutical inventions have largely controlled it globally – and here we saw reported rates fall by about 99 per cent last year, because of things like closed borders, lockdowns and more people getting their vaccination.

An estimated 200,000 Kiwis catch the flu every year - and 500 die with it. Photo / NZME

Overseas, many people have still been working from home and schools have moved online, so we haven't seen any big effect in other countries with flu yet.

While it might not come back in a big way this year, it will at some point, because it's still circulating, albeit at low levels, around the world.

For instance, a recent study showed there was still flu circulating around the US and southeast Asia, but with low genetic diversity.

Along with the fact we won't have much immunity, how influenza comes back could likely depend on sub-types of the virus.

Because lots of strains aren't well detected at the moment through surveillance programmes, that makes strain selection for the flu vaccines we receive much more difficult.

Is it likely we'll be through this Omicron wave before hospitals are dealing with seasonal ills?

Traditionally, seasonal illnesses like influenza are mainly monitored from around May to October, with peaks occurring from July to August.

Omicron waves overseas have been quite sharp and short, so I think it's quite likely we'll be through the worst of this wave by then.

Another thing we've seen so far overseas, is that there haven't been second Omicron waves yet.

We know Omicron tends to infect a lot of people – we're seeing it here right now – and although we know reinfection is possible, it still seems to be fairly rare, because people have developed immunity from vaccines or infections.

So, I don't see any reason why we'd also be dealing with a second wave on top of what else is circulating over winter.

But Covid-19 could still compound that seasonal pressure?

It certainly could. I'm actually expecting another variant to arrive by then. We don't know what that variant might look like, as there's a range of possibilities.

But we do know that variant will come – especially because we've shifted from eliminating Covid-19 to mitigating it, or trying to live with it.

So I'd expect our hospitals will be busy, whatever happens.

What can people do to ease this pressure?

I'd definitely recommend they get their flu vaccine when it becomes available in April.

Other than that, I'd encourage people to be mindful of all of the things we've used to minimise the spread of Covid-19, such as mask-wearing and staying home when sick.

All of those things are just as important for reducing the risk of other respiratory viruses.