A raft of earnings reports from consumer discretionary companies and US retail sales data set for the coming week could help investors determine to what extent the coronavirus is hitting consumer demand.

The S&P consumer discretionary sector has been among the index's best performers this year, gaining about 3.4% and trailing only the technology, utilities and communications services sectors.

But discretionary stocks could be in for a bumpy ride if companies warn that the coronavirus outbreak is weighing on their earnings outlook. Coronavirus concerns could also show up in the US retail sales report for January, due on Friday.

"It could have an impact on the year, not just the quarter," said Kim Forrest, chief investment officer at Bokeh Capital Partners in Pittsburgh. "People are going to freak out a little bit - you are going to have your retail investor that is going to say they don't want to be in (the sector) anymore because it's not growing."

Analysts expect retail sales to show an increase of 0.3% in January from the previous month, matching the increase seen for December.

Companies expected to report include Hilton Worldwide, Under Armour, MGM Resorts and Expedia Group. Coronavirus concerns have already weighed on some of these stocks - MGM shares tumbled around 10% in late January after the spreading outbreak shuttered casinos in Macau. But they rebounded more than 2% in the latest week.

In recent weeks KFC licensee Yum China said it could report an operating loss in the first quarter and take a significant hit to sales and productivity due to the coronavirus outbreak after it was forced to shut nearly a third of its stores in China.

The announcement came on the heels of a similar warning from US cafe chain Starbucks, which said it would delay a planned upward revision to its outlook for the year and expected a material but temporary financial hit.

Disruptions to the global supply chain caused by the coronavirus could also pressure consumer names. China accounts for over 10% of global trade in goods excluding energy and intermediate foods, Oxford Economics said in a report.

Some areas, such as capital goods - which are used to produce other goods or services - are likely to be at greater risk, the firm said.

Historically high valuations may also make some stocks in the sector more vulnerable to a pullback. The forward price-to-earnings ratio for the sector is over 22, approaching levels not seen since June 2009. That compares with its 20-year average of 18.3 and the current 18.5 for the broad S&P 500.

Companies that have expanded their online sales may be better able to weather disruptions, analysts said. "It may put the leaders in a big lead and the laggards in a bigger lag," said JJ Kinahan, chief market strategist at TD Ameritrade in Chicago. "We are going to continue to see the gap grow."