The latest RTÉ Morning Ireland Extra podcast looks at how you can shop safely and whether you should wash your groceries down when you get home.

As reported by Cian McCormack earlier this week, and outlined below, supermarkets are high-risk sites of infection for Covid-19, according to the Irish Global Health Network.

The network is an independent gathering of people concerned with health inequities globally.

Cian McCormack spoke to Niall Roche, of the Irish Global Health Network and TCD, as well as Dylan H Morris, a PhD candidate in Ecology and Evolutionary Biology at Princeton University.

The booklet is called, 'A quick guide to safe shopping during the Covid-19 pandemic'.

It advises on what to do before, during and after shopping, and how to assess whether your supermarket is doing enough to keep you safe. You can download a copy of the booklet here.

The Irish Global Health Network says it published the guide because some supermarkets were disregarding hygiene standards. 

Environmental health specialist Niall Roche, who is a board member of the Irish Global Health Network and an adjunct assistant Professor at the Centre for Global Health at Trinity College in Dublin, said he was "shocked at the level of overcrowding" at his local supermarket when he went there in the early days of the pandemic.

"I spoke to the manager to ask about what guidelines were going on in his particular supermarket and I didn't get a sense that there was a strong level of guidance within that particular store," he said.

He was looking for measures "to protect us as shoppers, to protect me as an individual, and to protect the staff within the supermarket".

Professor Roche acknowledges that a lot of progress has been made since those early days, when he witnessed uncovered bread on open display, and shop floor staff "bunched together stacking the shelves".

Now, it's commonplace to see hand sanitiser at supermarket entrances and markings on the floors to indicate the two-metre social distancing requirement.

"I know environmental health officers have been going around and supporting supermarkets and advising them on infection control measures they can take, and I know supermarkets are responding," he said.

But what about your groceries? How can you be sure you're not bringing the virus back into your home via the ingredients for your evening meal?

Dylan H Morris is a PhD candidate in Ecology and Evolutionary Biology at Princeton University in the US. He has investigated how long Covid-19 can live on surfaces.

He said: "We experimentally contaminated surfaces, in a safe lab environment, with some virus. And then we came back at regular time intervals to see if the virus was still infectious."

Mr Morris and his colleagues found that the virus lived longest on hard surfaces.

"On steel and plastic, the virus has a half life of six to eight hours, which means that, if you put some virus there, six to eight hours later, half of it would be gone," he said. 

"After another six to eight hours, half of that would be gone so a quarter of what was initially there would be left."

So how risky is it to bring those surfaces, in the form of your groceries, back into your house?

"I would say everyone has their own personal level of risk and I would encourage everyone to do what makes them most comfortable," he added.

First of all, cook your food properly.

It's known that severe heat is "a pretty good de-contaminator" and "the virus is going to struggle to do well".

"You should always wash anything you're going to eat raw," and it wouldn't hurt to give it a "slightly more aggressive scrub" in this period of uncertainty.

As for washing your dry goods, Mr Morris said it's a question of "risk reduction".

"None of us can eliminate all the risk in our lives but if you've been out in public and you wash your hands or if you've unwrapped something that was recently touched by someone else and thrown it away and then wash your hands again, it'll reduce the risk a bit.

"It'll never reduce it to zero but equally it's not going to be as high as if you didn't do that," added Mr Morris.