The chair of the Epidemiological Modelling Group advising the National Public Health Emergency Team has said there is a "real danger" of a second wave of virus cases, if the changing of restrictions in place is not done correctly.

The Taoiseach announced on Friday that the Covid-19 restrictions will be extended for a further three weeks until Tuesday 5 May.

Among the measures are physical distancing, travel restrictions and cocooning for all those aged 70 and above.

Speaking on RTÉ's This Week programme, Professor Philip Nolan said as we look to modifying restrictions to allow people get back to more activity, there was a "real danger" if not done carefully that we will get a second Covid-19 wave.

If done wrong, he said, we would see a rapid re-emergence of the disease, as well as a rise to a "potentially very dangerous peak".

He said what we do after 5 May is critical to determining whether we are past a peak or facing into a new and dangerous one.

Prof Nolan said right now however, we seem to be in a "very stable situation".

On the likelihood of a lifting of restrictions post 5 May, Prof Nolan said it would be reasonable to consider changing them, only if the measures currently in place result in a significant reduction in the reproduction number of the virus to below one by then.

He said there are many things we can do safely without transferring the virus to other people, and as a society we need to think carefully about the things we can get back to doing in a way that does not spread the virus.

The latest figures show that the total number of Covid-19 cases in the Republic of Ireland has risen to 8,928, with 320 people reported dead.

Prof Nolan also said deferring the Leaving Cert was precisely the right decision.

He said that data coming back to them in terms of positive test results from Irish tests in German labs is reinforcing their belief that the number of cases is stable here and so the disease is under control.

He said they need to have a top class testing regiment in place if restrictions are to be lifted.

Prof Nolan also said people who have the disease may have no symptoms, but are still infectious for a day or two before they show symptoms.

He said given this, somebody who develops symptoms will be spreading the virus for days before they ever get tested, even if you have the best testing regiment in the world.

Prof Nolan said someone who might not have symptoms needs to act as if there is a possibility that they have the virus.

Testing is useful in terms of monitoring the disease, he said, but is not useful in terms of "don't worry now, you've been tested and you're not infected".

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