Markets react to new information discounted by uncertainty.
Only from my memory, I think news about the coronavirus relief bill (CARES Act) changed over the weekend. I think that's when it became clear the amount was closer to $2 trillion. If I remembered it accurately, that would mean Monday (March 20) was the first chance to reflect that information in the market, less the uncertainty of Congress approving it. On Monday the U.S. stock market went up +9%.
Last week, news articles criticised the U.S. for a lack of testing. This week, the news agrees that technically U.S. testing has passed Korea, but has a larger population. That is probably being digested by the media and markets.
That's why I was the first person to pick "The beginning of quick run back up, markets no longer spooked". Including the words "keep the party going" after that creates a biased poll, since it sounds ignorant and none of the other choices include that type of language. The poll would be more fair with those words removed.