One of the main non-pharmaceutical measures includes case isolation and contact tracing. However, studies have shown that isolation and tracing are effective only if the infectiousness is possible after occurring of symptoms, as in the case of SARS. If the infection appears before the onset of symptoms (pre-symptomatically), as in the case of COVID-19, these measures begin to lose their effectiveness along with an increase of the transmission probability before the onset of symptoms. This proves that additional non-pharmaceutical measures are needed to prevent COVID-19, for example, wearing masks. In current study we used a stochastic model and evaluated the impact of non-pharmaceutical interventions such as case isolation, contact tracing, and wearing of masks. By varying the scenarios and probabilities of masks wearing, we demonstrate that in addition to basic interventions (isolation and tracing), a broadly use of masks by general public is necessary to control and prevent the disease transmission.