Mathematical misconceptions about flattening the curve

The duration of intervention measures may not be important if the transmission rate returns to normal when measures are loosened, and the mortality rate remains the same. - NSTP file pic

The  duration of intervention measures may not be important if the transmission rate returns to normal when measures are loosened, and the mortality rate remains the same. – NSTP file pic

LETTERS: It was claimed that the third wave of Covid-19 cases in Malaysia was due to the public’s failure to adhere to the standard operating procedures (SOP). While some experts attributed it to pandemic fatigue, this letter discusses another possible factor — the mathematical misconceptions about flattening the curve (FTC).

You may have seen the FTC graph consisting of a tall, narrow curve and a short, wide curve. The curve being flattened represents the projected number of cases over time. There is a line through the graph that shows the number of patients the healthcare system can treat.

The tall curve goes above the line, which means there are too many patients at one time. The flattened curve shows what happens if the spread of the virus slows down. The roots of FTC can be traced back to a paper published in 2007 by the Centre for Disease Control and Prevention in the United States, which was a preview to a pandemic like Covid-19.

Today, the term has become a rallying cry in the fight against the Covid-19 pandemic. FTC is a useful and succinct way of conveying the importance of intervention measures and SOP to the public in taking the burden off the healthcare system. This will buy us time to devise more efficient and sustainable initiatives, enhance the capability of the healthcare system and, possibly, develop a vaccine.

The first misconception is the notion that using the FTC approach, the same number of people may get infected, but will lengthen the duration of the pandemic. However, using a SIR (susceptible, infected, recovered) model, a recent study shows that effective implementation of intervention measures can reduce the number of susceptible individuals and the peak number of cases, eventually shortening the duration of the pandemic.

Therefore, we can decrease the number of cases and fatalities with public health measures, without prolonging the lockdown and other extreme measures.

The second misconception is due to a typically missing part of the often-cited FTC graph; what will happen after the curve is flattened? As many countries are loosening lockdowns and other measures, the public may be misled into thinking that the Covid-19 pandemic is ending, and our life will return to normal once the graph is successfully flattened.

However, many studies have shown that even if the measures are successful in flattening the curve initially, the number of cases will oscillate like a sine wave. The duration of intervention measures may not be important if the transmission rate returns to normal when measures are loosened, and the mortality rate remains the same.

Easing the control measures, and in the absence of other interventions, cases will increase exponentially again, unless a large majority of the population has developed immunity (either from recovered infection or an effective vaccine) or the infectious agent has been eliminated, without any possibility of reemergence.

This might explain the resurgence of Covid-19 cases in Malaysia recently. As a solution, some researchers from Harvard University suggest intermittent physical distancing measures through 2022 to prevent the healthcare system from being overwhelmed.

To sum up, a correct understanding of FTC will find the optimal duration and frequency of its implementation to achieve a perfect balance between health, economy and social wellbeing.

by DR AUNI ASLAH MAT DAUD.

Read more @ https://www.nst.com.my/opinion/letters/2020/11/642993/mathematical-misconceptions-about-flattening-curve

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