‘Flattening the curve’,

‘community spread’ and ‘herd immunity’ are all terms that we’ve become familiar

with due to the coronavirus pandemic.

You can now add ‘R’ value to

the ever-growing number of buzz words associated with the virus.

Like testing, the R value is

being touted as an important tool that countries can use to assess their level

of readiness, as it relates to the reopening of the economy.

What is an R Value?

 The R value or

‘reproductive number’ is a way of rating a disease’s ability to

spread. The term, which is primarily used in epidemiology, is a model that

is used to determine the average number of people that one infected person will

pass the virus to.

The R value isn’t a fixed

number, so it can be affected by a range of factors including location.

The R value for the coronavirus

for example can vary from country to country, based on how densely populated

the area is.

Given that Sars-CoV-2 – the

proper name for the coronavirus– is a new pathogen scientist initially had to

calculate its R0, pronounced ‘R nought’.

The R nought value assumes that

a population is wholly susceptible at the beginning.

It further assumes that at the

time there would be no suppression measures, and it also assumes that there are

no individuals who are immune.

Early studies indicated that

China may have initially had a R value of between 2 and 2.5

What is an ideal R value?

Increasingly, we’ve all heard

countries like the UK and Germany make reference to an R value that is less

than 1.

An R value of more than 1

indicates the possibility of an outbreak or pandemic.

A R value greater than 1 can

mean a variety of things including a wave of new infections.

Given that R values are

calculated daily and may often vary, the objective is to have an R value of

below 1 for a sustained period of time, which could mean that the virus is on

the decline and eventually die out.

An R value of 0.75 means that

each sick person is transmitting the virus to less than one other person- this

is a positive indication that could be used to make decisions about the

reopening of the economy.

Is calculating an R value ideal

for small island states like Jamaica?

While the R value can be an

important piece of data that countries use to make decisions, the R value may

not be useful for smaller Caribbean states, like Jamaica.

According to a local

epidemiologist, the problem with calculating R values for smaller countries is

the inputs needed to calculate the number.

The epidemiologist told BUZZ that a country would need a

minimum of 60 new cases per day or a population of 3 to 5 million to get any

sensible values.

Similarly, Chief Medical Officer

for the Cayman Islands, Dr John Lee, said that because there are many different

ways of calculating the R value, but with much of the math rooted in

guesses, it may not be the most accurate measure.

“The R value also relates to

whole populations and as you are aware, we have had a number of different

clusters of cases and each of those clusters of cases will have its own

reproductive number; which is different from the R value of the whole

community. What people want is to know the R value for the whole

community,” said Lee.

“I am saying that these

clusters throw off the calculation and immediately lets you understand that

when you look at a small population where there is not a lot of infection going

on, it becomes a fairly meaningless figure,” added Lee.

The coronavirus has a median R

value of 5.7, according to a study published online in an online medical

journal.

Similarly, infectious diseases such as polio, smallpox and rubella have R

nought values in the 5 to 7 range.

According to the Centers for

Disease Control and Prevention polio and smallpox are among the nine deadliest

viruses on earth.

Ebola which is widely considered

to be exceptionally contagious, has an R value of only 1.5 to 2.