Shares of retailers and other consumer companies rose after more positive data from the U.S. property market.

Sales of previously owned homes rose in August for the third consecutive month of sales increases, with a 2.4% gain from the previous month, the National Association of Realtors said.

Cruiseline Carnival Corp. is laying off more than 100 ship officers as the company sheds 18 less-efficient vessels from its fleet across various brands, The Wall Street Journal reported. Cruise operators haven't been sailing in the U.S. for about six months due to the Covid-19 pandemic.

The levels of Covid-19 in the U.S. will be pivotal for sectors such as consumer discretionary and the stock market as a whole, said one strategist.

"It's a big risk to the market," said Eric Marshall, president of Dallas mutual-fund firm Hodges Capital.

"If we were to see another major shutdown, I think there are a lot of areas of our economy that would find it very difficult to withstand it.

Movie theaters, restaurants and all the ones that have held on for the last six months." In such a precarious state after the last shutdown, many of these companies might not survive a second one, Mr. Marshall said.

Write to Rob Curran at rob.curran@dowjones.com