C-19: A likely candidate for an exit strategy

Updated: May 11

In this article we attempt to directly address 3 major questions (for the case of Malaysia);

(A) Crudely speaking, how could we go about objectively defining an acceptable threshold of infections and deaths from COVID-19?

(B) How could we (therefore) devise a workable strategy of utilising and moderating movement controls over the next 1-1.5 years until a vaccine is introduced?

(C) Will we realistically ever be able to go back to normal life (i.e. how things were before COVID-19)?

Answer:

In Malaysia, cardiovascular diseases for example kill 260 people per 100,000 per year, cancer some 130 people, and smoking roughly 100. Data for Malaysia and a number of other countries is included in the figures further below for the readers reference.

Let us assume that we could be accepting to a prevalence of COVID-19 deaths that is well within the range indicated by these other disease causes. For example, an annual death threshold of ~10 per 100,000 persons due to COVID-19 (10 times less than smoking), for example, would translate to some 3,100 deaths per year or 8.5 deaths per day on average. This is a far lower figure than death prevalence caused by any other type of disease based on statistical records, and hopefully answers our first question.

The figure below illustrates a hypothetical situation of switching movement controls and lock-downs on and off alternately over the next 12 months, where the first wave is the current one Malaysia is encountering. The specific assumptions made to construct this projection are similar to what we had modelled in a previous article, where current COVID-19 trajectory statistics are used as input assumptions. As mentioned before, we assume a minor progressive improvement to the uncontrolled transmission rate over time, reflecting a more attentive and conscientious population that would take precautions to keep the spread of the virus at bay, regardless of lock-downs.

In summary, over the course of 12 months, the country could stay open for some 250 days, with lock-downs totalling 120 days. This includes the extended lockdown currently in place totalling some 6-7 weeks (so far). Based on projections, an on and off lock down strategy would translate to a cumulative total of 200,000 people infected by the end of the 12 months, where at any one time the average number of infectious persons could be kept below 7,700 (assuming a 14 day infectious window). Deaths are capped at 2,000 for the year or 5.5 per day, translating to a death prevalence of 6.4 per 100,000 persons.

This answers the second question.

In short, the answer to the third question is no, there will be no normal life until a vaccine is introduced regardless of whether lock-downs are in place. Namely, and amongst many many other scenarios that need further debating, we may not find a 100% robust answer as to how to deal with the following activities for some time;

  • International travel - due to potential cross-border transmission of the virus, while standards in testing and control procedures vary across countries; and temporary isolation due to test turnaround could be costly

  • Public transportation systems and hubs - due to the major role it played as a high potential vector for transmission in the US and European countries; in terms of congregation of large crowds, but also closed loop air-cond circulation systems in vehicles

  • Public events (e.g. weddings, conferences) - congregation of large crowds in an enclosed space for a significant amount of time, and under close air circulation

  • Schooling activities - the role of children as asymptomatic carriers, i.e. they can carry the virus back home to parents or older relatives who could be more susceptible to complications from the virus

**Update: 2nd May 2020:

We have updated this model by using our derived mobility to infection regressions - see figures below. They key difference between this and the previous model is in allowing a more gradual increase (or reduction) of mobility as lock-downs are lifted or reintroduced. Salient assumptions are;

  • Initial growth transmission factor = 1.2 / 3.8 days to double

  • Regression used: Tr-factor = Mobility (in %) x .358 + 0.842 (loosely based on UK regression)

  • Time for mobility to reach peak, or taper to low mobility levels ~1.5 weeks

  • Assumed progressive improvement to transmission factor at decline -0.03% per day

  • Total infected (365 days) = 78,000 or 190 per day / total deaths = 660 or 2 deaths per day


Reference data and figures section

(i) Malaysia: death numbers by cause

(ii) Southeast Asia: death numbers by cause

(iii) Deaths per 100,000 population for selected countries due to listed causes 1990-2017

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