The R factor: the digit that is shaping our lives

Since the pandemic began, the R0 number has been pored over on a daily basis by medics and the media. Whenever it rises to 1 or more, alarm ensues. But just how effective is it at telling us the rate of coronavirus infection?

Lines of healthcare professionals enter a public housing complex in Melbourne, Australia: further lockdown measures for residents in Melbourne came into effect last week. They will be in place for six weeks. Picture: Getty

During the Covid-19 pandemic, whatever digit happens to follow the letter “R” has become the magic number, jumping from the pages of academic journals into regular discourse of politicians, media and the general public. It has been framed as a number that will shape everyone’s lives. In many countries, including Ireland, it is reported on a regular basis – sometimes every week.

Last week, the National Public Health Emergency Team (NPHET) warned that there was ...