Once the figure drops below one, the number of cases begin to lower.
The National Public Health Emergency Team is meeting to discuss how much progress has been made to suppress the virus since level five restrictions came into effect.
It will look at the 14 day incidence rate, the number of hospitalisations and overall compliance with the measures.
The 'R' number is now estimated to be below 1, but the Taoiseach has said it's unlikely restrictions will be eased earlier than planned.
Immunology expert, Professor Kingston Mills thinks the situation looks positive.