Monetary policy does not have an effect on the supply side, but can work to ensure demand is stronger than it otherwise would be. Lower interest rates will provide more disposable income to the household sector and those businesses with debt.
They may not spend it straight away, but it brings forward the day when they will be comfortable with their balance sheets and resume a normal pattern of spending. Monetary policy also works through the exchange rate which will help mitigate the effect of the virus' impact on external demand. The effect of the virus will come to an end at some point.