Japan’s benchmark Nikkei 225 lost earlier gains and dropped 1.6% to 27,821.76, as pessimism over the Omicron variant set in.
Some analysts think a serious economic downturn, like what happened last year, likely will be averted because many people have been vaccinated.
The vaccination rollout rate varies by country in the region, at about 77% in Japan, 50% in Vietnam and 35% in Indonesia.
On Wall Street, the S&P 500 rose 1.3% to 4,655.27, recovering more than half of its drop Friday, which was its worst since February.
The VIX, an index that measures how worried investors are about upcoming drops for the S&P 500, eased significantly.
But while the market steadied itself, Omicron adds more risk to a global economy already contending with paralyzing uncertainty.
Travel bans, including decisions by Japan and Israel to bar foreign visitors, threaten to disrupt global business.
Shipping problems would risk pushing prices higher, adding to inflation pressures.
Besides waiting on more clues about how much economic damage Omicron will ultimately do, the market has several big mileposts this week that could swing prices.
And that uncertainty in the meantime could lead to more up-and-down swings for the stock market, which has surged more than 24% this year and set a record as recently as Nov.