What is R0 (R-naught) and why is it important?

In an effort for to flatten the COVID-19 curve, the R0 becomes a tool to measure the rate of COVID-19 infectivity in Malaysia for the government to plan its next move.

What is R0 (R-naught)?

R0, pronounced as R-naught, is a mathematical term that measures how contagious an infectious disease is or how easily it spreads from person to person in a community. It is also known as the reproduction number.

The R0 value shows the average number of persons who will contract the disease from one person that has the disease.

For example, for an R0 value of 2, a person who has the disease will transmit the disease to an average of 2 people, and so will each person who contracted the disease henceforth.

More infectious diseases typically have higher R0 such as Measles with an R0 between 12 to 18. With the given value, every person infected with measles will pass it on to an additional 12 to 18 people.

On the other end, MERS, or Middle East Respiratory Syndrome, has an R0 less than 1, making it less likely to develop into a full-blown outbreak.

R0 for COVID-19 is estimated to be between 2 and 4.

What is our current R0 value?

The R0 value of COVID-19 infection transmission in the country remains above 1, as monitored by the Ministry of Health (MoH). The latest value as of September 13, 2020 is 1.58.

Last week, Health Director-general Tan Sri Dr Noor Hisham Abdullah confirmed the R0 in Selangor has increased to an estimated 1.95 as new cases surge in the state.

The R0 in Sabah which stood at 1.26 has started to stabilize. However, the R0 could easily increase again without public health intervention.

The estimated R0 for Kedah has dropped to 0.65 following reductions in daily new confirmed cases.

Why it matters?

Though the use of R0 has its limitations, it has been used by many governments worldwide to stay ahead in their responses to the COVID-19 outbreak. The R0 value can determine a few possible outcomes.

If an R0 value is less than 1, the existing infectious disease will cause less than one new infection which will lead to the outbreak eventually dying out.

Whereas if an R0 is more than 1, the existing infectious disease will cause more than one new infection leading to a higher level of disease transmission and a possibility of the outbreak lasting longer.

A smaller R0 value can assist in the contact tracing process as well, as there are fewer people that would be infected. It will ultimately act as an incentive for the government to implement strategies in favour of the people such as easing lockdown measures.

To bring down the R0 would require for everyone to strictly abide by the COVID-19 prevention measures such as wearing face mask, maintaining physical distance and ensuring good personal hygiene.