The announcement that the reproduction number for Covid-19 has dropped below 1 is yet another piece of good news in relation to the State’s efforts to combat the second surge of the disease here.
You have to go back to early July for a time when this metric, also known as the “R0”, was this low in the State.
An R0 of 1 means that each person with Covid-19 goes on to infect one other person. A higher value for the R0 means the pandemic will spread as infected persons go on to infect others; a lower value means the disease will eventually die out.
Estimates of the basic R0 of the virus vary, with studies indicating a value of more than 4 in the absence of preventative measures.
The basics of infection control – handwashing, distancing, masks – have helped keep the R0 below 1.8 here in recent months, but that still meant case numbers continued to increase. As case numbers continued to multiply, the Government was forced to tighten restrictions to Level 5 last month.
Public health doctors here are learning fast about the efficacy of the different restrictions under the Government's five-level framework. They believe Level 2 measures failed to prevent the virus growing, while Level 3 worked outside Dublin in specific circumstances. In Dublin, Level 3 worked for a few weeks, but then case numbers "flatlined" instead of falling, as Minister for Health Stephen Donnelly pointed out on Wednesday.
The enhanced Level 3 measures that were put in place, along with Level 4 in the Border counties, worked very well, he said, and are largely to credit for the improvement in our figures.
The further effect of Level 5 measures won’t be known until next week, but the restrictions are likely to ensure case numbers fall further.
Falling short
The question is whether the case numbers fall fast and far enough. The R0 is now at 0.7-0.9, Mr Donnelly has indicated, but this is well shy of the 0.5 public health officials aspired to for the entire six-week period of the current Level 5 restrictions.
Officials said six weeks of the R0 at 0.5 would see daily case numbers driven down to under 100 by early December.
The question facing the Government at that stage will be whether to take the foot off the pedal, and thereby allow businesses to reopen in time for the crucial Christmas period, or to continue with restrictions that choke transmission of the virus further but also choke the economy.
And while valuable knowledge is being garnered about ways of fine-tuning restrictions, this is a difficult seesaw to balance without it tipping in one direction or the other.