Kingston Mills says the virus will spread if people break the rules.
The Taoiseach and a group of senior ministers will meet today to consider whether to move the country to level five restrictions.
NPHET has recommended every county moves to that level, which would force everyone to stay within 5 kilometres of their home.
Another 1,000 cases of Covid-19 were confirmed yesterday, and three more deaths.
Chief Medical Officer Tony Holohan says the situation's 'extremely concerning' and is urging people to keep social contact to an 'absolute minimum'.
Dr Eoghan de Barra, a consultant in infectious diseases in Beaumont Hospital in Dublin, says only some counties need more restrictions.
Gardai will be patrolling parks and beauty spots this weekend to make sure people are sticking to the current restrictions.
Cavan, Monaghan and Donegal are at level four, while every other county's at level 3.
A high-visibility Garda operation will be in place throughout the weekend.
Immunology professor and Mullingar's Kingston Mills, from Trinity College, says the current crisis will continue until spring if people break the rules: