The first-order effect is a drastic fall in labor (L) for one quarter (hopefully no more). GDP doesn’t fall from trees, less L means less Y. Inevitably. Only a small fraction of labor at work can be substituted by labor from home.
Focus policy right now on responding to the health emergency, funding health care, producing ventilators. Not on the stock market or the macroeconomy.
If economy can offset lost production now by people working nights and weekends in the next few quarters, can stabilize GDP over 1-2 years. Then, focus of policy is on easing *intertemporal substitution*.