By: Steve Bond, BScPhm, RPh, CDE
Many new terms have come to light during the recent pandemic. One such term is the “R-value” – a number that is often quoted by politicians and healthcare providers. But what is “R” and why does it matter? The R value is a statistical term that measures the Reproduction within a population. If this number is 1 for example, each person/bird/mouse would produce 1 offspring and the population would neither grow or shrink. If the number is above 1, the population grows and if less than 1 it shrinks.
This same number is applied to viruses; for example, an R of 2 would mean 2 people with the Coronavirus would likely go on to infect 4 people. Those 4 would in turn transmit it to 8 people and so on. When the R is above 1, the virus will grow exponentially within a population with no immunity. At 1, it stays steady. Below 1, the virus will gradually infect fewer people, until the epidemic dries up.
There are many factors that impact this number. First of all, some viruses are more contagious than others. For example, the omicron variant seems to be more contagious than previous variants. Changes to the outer surface of the virus can help it to infect human cells. This is kind of like a person who is exceptionally tall being good at a sport like basketball. Even though they still have to work to be good, they have an advantage over a shorter player. We can affect the R value as well. Getting vaccinated, limiting exposure to small groups, wearing proper protective equipment and isolating when you may be infected, can greatly reduce this number.
There are some limitations to the R value. First of all, since we cannot measure who is infected or not this second, we need to rely on historical data. This means looking back 7, 10 or 14 days to see positive results, hospitalizations or deaths. With a virus that moves quickly, this can over or underestimate the value. Secondly, it is greatly dependent on human routine or behaviour. The value can escalate if we become contented and let our guards down.
So let’s work together to reduce that R value. Let’s take care of ourselves and each other,