When collecting incidence data of common and mild diseases, we expect low incidence reporting rates because: (1) some infected individuals do not show symptoms (sub-clinical cases); and (2) some others choose not to consult doctors despite showing symptoms (unreported cases). In countries where consultation fees are high, we expect the latter to be dominant. Fortunately, the low reporting rates are compensated by the large volume of daily incidences generated by such diseases. We also note that voluntary reporting rates in Singapore are relatively high because of the low consultation fees, making the strategy for estimating the infection network presented below attractive.