Llanelli AM Lee Waters has taken to Twitter raising his concerns about the number of people ignoring social distancing advice.
It comes following reports of people walking in groups along the Millennium Coastal Path between Llanelli and Pembrey and Swansea seafront.
Those using Wales' countryside as an escape from coronavirus have been criticised as "irresponsible".
People with second homes, caravans and campervans have been travelling in search of isolation in recent days.
Lee Waters says: "There's a hint of spring in the air. People are out with their dogs on their bikes with their dogs as they were yesterday. Reports from all over Llanelli, within Mumbles, Porthcawl. People are out in their droves as if it is a normal weekend and it's not. As I speak hospitals are converting their canteens into spill over intensive care units. Their canteens!
"They are drawing back into service retired nurses and doctors and fast tracking into service third year medical students and scouring the land for ventilators. If this virus spreads like it has in Italy - the signs are similar - there was a big spike here yesterday - then thousands of people are not going to breathe without a machine. We don't have enough machines. We are trying to build new ones.
"We are retraining nurses and doctors who do hip operations to operate ventilators - but really we must make sure that we slow the spread this virus to give them a fighting chance to get up and ready for this. Our behaviour to date is not doing that. People are overreacting by panic buying but not enough people are reacting. We don't need to panic but we do need to listen to the advice."
THIS IS NOT A NORMAL SUNDAY! pic.twitter.com/mKP4hjrTTX— Lee Waters AM (@Amanwy) March 22, 2020