A Heuristic Model for Spreading of COVID 19 in Singapore

Fook Hou Lee

The model can be extended to asymptomatic spread, although this requires some re-organization of the spreadsheet, since the detected and undetected cases arising from each day of the asymptomatic period need to be tracked. There is also a possibility that the k and r-values may differ between asymptomatic and symptomatic periods. To cater for this, separate parameters are used for asymptomatic and symptomatic period; these being designated as ka and ks, and ra and rs, where the subscripts a and s denote asymptomatic and symptomatic parameter. Fig. 8 shows the effect of asymptomatic period on the overall spreading for the values of k and r as shown in Table 2 . The main effect of a low asymptomatic detection efficiency is a slower pick-up in the initial number of detected cases; but this is more than offset by a faster pick-up as the larger number of symptomatic cases kicks in. Not much is known about the asymptomatic detection efficiency but one may surmise that this should be lower than the symptomatic value. The asymptomatic daily infectivity is also highly debated.