The Executive Director of the World Health Organization's Emergencies Programme has said there has been an ongoing shift in Covid-19 being detected in younger adults.

Dr Mike Ryan said the shift into the disease being detected in the younger population is probably because they are the ones who came back into society more quickly by returning to work and college.

Speaking on RTÉ's Today with Claire Byrne, Dr Ryan said that although younger people may suffer a less severe version of the disease, it is not guaranteed that this will be the case and that there is always the risk of passing it to older populations.

If the disease is passed onto older generations again, he said, the hospitals will refill and "this is not something we want to see".

Dr Ryan said it is not known yet about what kind of protection people will have if they contract the disease.

He said that all viruses evolve and change over time, but so far there has not been any change in the virus that is associated with any significant change in the clinical syndrome or severity of the virus.

However, he warned it remains a very dangerous disease.

Dr Ryan said the rate in Ireland is still pretty good compared to other countries, despite the numbers of Covid-19 cases here having increased.

Dr Ryan said children do not seem to participate in the transmission of the virus in the same way as adults do, but there is no zero risk.

He said that Ireland has been very diligent in its reopening of schools and praised teachers and school administrators for the work they put into reopening schools.

Dr Ryan said that if people are in a properly ventilated classroom and are properly separated, they may not need a mask. However, he said it is all about the risk.

He said we must avoid amplifying events, whereby one event can result in one case causing a flare up in an area.

When asked about reopening the pubs, he said opening any environment is potentially safe, so long as it is done in a safe way, adding that it is not about the pubs themselves but the way in which people behave in them.

He said that the primary focus must be on containing community transmission, wearing masks, maintaining physical distance and hygiene. He said the Government can only advise people on the best way to behave.

Confidence over vaccine

Dr Ryan said he was confident that a vaccine would be found but that "we cannot push too hard and too fast".

He said it was right that the Oxford group and AstraZeneca paused their trial, adding that there are six other vaccines at phase three level another 32 other tentative vaccines.

He added that not all vaccines succeed or can be proven to be fully safe.

Dr Ryan said governments deserve some space in order to get the balance between economy, society and public health right and we need to avoid a "flip flop" situation.

He said consistent policy needs to be implemented for long enough to see if it works and if it does not work, then policies must be allowed change without recrimination.

Dr Ryan said it is not helpful if "controlling a virus turns into a political polemic".

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He said that he knows people are tired, but we have to learn how to live with Covid-19 and that there are things we can do.

The incidence of the virus in Ireland is still relatively low, he said, and people can take the necessary precautions.

Dr Ryan said that special consideration for air travel needs to be given to Ireland, an island nation with an economy based on trade and tourism.

He said everyone needs to consider their need for travel and a lot of guidance has been issued to travel companies and airlines.

In addition, he said, people must be tracked and followed up when they arrive so they do not pose a risk to local communities.

Dr Ryan said anyone arriving in a new country has a responsibility to make sure they do not contribute to the problem.

He said that testing at airports can be helpful, but will not bring the risk down to zero. In general, he said, a 14-day quarantine and follow up is best.

Dr Ryan said people need to know when they need to wear a mask, adding that we do not want to be in a situation where people can no longer tolerate wearing a mask and stop altogether.