Shifting Covid-19 Epicentre May Explain Prolonged National Infection Wave — Sean Wen

We must continue monitoring the infection rates so that targeted intervention and implementation can be planned and executed in a timely manner.

I refer to the article Prepare For The Delta Wave Of Covid-19 Outside The Klang Valley, published on CodeBlue on July 26, 2021. The article described the increase in Covid-19 cases admitted to intensive care units (ICU) in several states, namely Perak, Kedah, and Penang.

Malaysia has undergone two waves of infection since the first recorded Covid-19 case on February 4, 2020. The first wave was from March to May 2020, while the second wave was from January to March 2021.

Just when we thought we were out of the woods, the number of new cases began to increase exponentially again in May 2021 with no signs of abating. Indeed, Malaysia reported a new record of 17,786 cases on July 31.

The total number of daily new cases in the country perennially make the daily headlines, with Selangor and Kuala Lumpur bearing the bulk of the blame for the ongoing wave of infection. Indeed, Selangor has consistently recorded the highest number of daily new cases since this new wave of infection began.

Nevertheless, the continued increase in new cases may hint at emerging epicentres outside of the Klang Valley. However, focusing on only the national daily new cases does not reveal trends in states with smaller populations relative to more populous states such as Selangor.

Moreover, a systematic and unbiased comparison of daily new cases between states is currently unavailable.

To this end, we have conducted an analysis to identify and compare patterns between states. To ensure that the comparison is unbiased, we implemented the following approaches.

By implementing these approaches, we can ensure, to the best of our abilities, that infection rates in smaller states do not go unnoticed.

  1. For each state, we normalised the daily number of new cases with its corresponding population size. This will result in every state having the same unit of measurement for infection rates and enable fair comparison across all states. Specifically, the infection rates are represented by the number of daily new cases per 100,000 population.
  2. We chose 100,000 population as the common denominator to represent the infection rates because Labuan has the smallest population, with approximately 100,000 people (99,600 to be precise).
  3. We used the seven-day moving average to represent the infection rates rather than the individual values of number of daily new cases. This is to even (regress) out factors that may lead to disproportionately high or low number of reported daily new cases on certain days. One such factor is the variability of testing rates from one day to another. 
  4. We stratified the states into Peninsular Malaysia (West and East Coasts) and East Malaysia to prevent overcrowding of the graphs and to group states into geographically related states.
  5. The infection rates of every state are represented on similar scales on the graphs to enable easy and fair comparison. For example, all states within Peninsular Malaysia are plotted using 0 to 125 new cases per 100,000 population, whereas states within East Malaysia are plotted within 0 to 200 new cases per 100,000 population.

From our analysis, several conclusions were reached:

  1. As of end of July, both Kuala Lumpur and Selangor have the highest national infection rates with 124 and 111 daily new cases per 100,000 population. Outside of Selangor and Kuala Lumpur, states that demonstrate increasing infection rates are Putrajaya, Melaka, Kedah, Penang, and Perak.
  2. Overall, the infection rate in Peninsular Malaysia (West Coast) is higher compared to Peninsular Malaysia (East Coast) and East Malaysia. 
  3. The spike in infection rates in Negeri Sembilan in mid-July may be explained by targeted screening and close-contact screening carried out by employers from the industrial sector.
  4. The spike in infection rates in Labuan in June led to a total lockdown from June 15 to 28.  The high infection rates combined with high vaccination rates have been proposed as the reasons for Labuan to be the first area in the country to achieve herd immunity against Covid-19.

It would be of particular importance to continue monitoring the infection rates at both the national and state levels to ensure all states, big and small, are critically scrutinised, so that targeted intervention and implementation can be planned and executed in a timely manner.

Sean Wen is a DPhil student in Medical Sciences at the University of Oxford.

  • This is the personal opinion of the writer or publication and does not necessarily represent the views of CodeBlue.

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