Coronavirus: What is the Reproduction (R) Number?
At the heart of understanding the threat posed by COVID-19, is a crucial number, the Reproduction number - a way of rating a disease's ability to spread.
It's the average number of people each infected person passes their infection to.
It is calculated backwards using data - such as the number of people dying, active cases.
This allows you to estimate how easily the virus is spreading.
The R number needs to be below one, if higher, then the number of cases increases exponentially.
But if the R value is lower, the disease will eventually fizzle out as not enough new people are being infected to sustain the outbreak.
Although estimates vary, the novel coronavirus, known officially as SARS-CoV-2, has a reproduction number of about three globally.
This number varies in and within different countries.
This uncertainty stems from a variety of related unknowns, which include:
- First, how contagious is the virus?
- Second, how many people have actually been infected so far?
- What proportion of infected people never have symptoms?
Such figures remain highly disputed because we simply aren't testing enough people to know how many infections there really are.
As Kenya and any other country for that matter contemplates lifting lockdown measures and restrictions, the aim will be to keep the Reproduction number closer to zero as possible.
Whichever way, we still have to keep the infection rate down through the laid down protocols advised by the health authorities.