U.S. companies buffeted by supply chain chaos and a growing awareness of the scope of a viral outbreak are facing new threats to begin the week. The price of U.S. crude fell as much as 34% to $27.34 a barrel, the lowest price since early 2016, as an oil war between Saudi Arabia and Russia broke out. Typically, falling energy prices are good for markets and for businesses. However, in times of economic duress, energy prices come to be seen as a barometer of the global economy overall. That appeared to be what happened Monday with crude prices suffering the largest single-day decline since the 1991 Gulf War. Here are some of the developments that are affecting businesses and potentially, the economy as a whole.