stock futures dropped in overnight trading on Thursday as investors geared up for a shortened trading day amid renewed Covid fears over a new variant found in South Africa.

The downward move in futures came after WHO officials on Thursday warned of a new Covid-19 variant that's been detected in South Africa.

Markets were closed on Thursday for Thanksgiving, so stocks are coming off of slight gains on Wednesday that staunched the week's losses for the S&P 500 and Nasdaq Composite.

The Nasdaq is down 1.3% for the week, while the S&P 500 is up less than 0.1% and the Dow has gained roughly 0.6%.

Friday also marks the unofficial start of the holiday shopping season, as investors will be looking for insight from Black Friday to determine the mood of the U.S.

On Wednesday, shares of Gap and Nordstrom tanked more than 20%, but Kohl's jumped more than 10% a week ago after reporting strong sales growth.

It also remains to be seen if discussion around supply chain issues caused consumers to start their holiday shopping early, potentially denting fourth-quarter sales.