The stock market has been extremely volatile for a while now, and Thursday morning brought renewed pressure amid greater concerns about the likely impact of the novel coronavirus on the U.S. population. The governor of California declared a state of emergency following the first death of a state resident from the virus, further ramping up the alert level over the COVID-19 outbreak. As of 11 a.m. EST, the Dow Jones Industrial Average (^DJI -1.24%) was down 690 points to 26,401. The S&P 500 (^GSPC -1.46%) fell 73 points to 3,057, and the Nasdaq Composite (^IXIC -1.62%) dropped 162 points to 8,856.

Consumer response to the coronavirus threat has had a mixed impact on different companies. Shares of warehouse retailer Costco Wholesale (COST -0.14%) rose as investors saw some potential positives for the company from the demand for goods in anticipation of possible measures to fight the outbreak. However, United Airlines Holdings (UAL -2.88%) cut back on domestic flights, expecting the lull in travel to continue for some time.

Costco has what people want

Shares of Costco Wholesale were up slightly on Thursday morning, defying the market's drop. The retailer has already seen signs of panic-buying among those seeking to stockpile vital goods, and investors are curious to see how that trend might show up in the company's fiscal second-quarter financial report due out later today.

Front of Costco store location, with store logo above the opening.

Image source: Costco Wholesale.

Already, reports from Costco locations have shown increased demand for items like bottled water, baby wipes, toilet paper, and hand sanitizer. Photos featuring empty shelves have sprouted on television and internet media outlets, and some stores have imposed limits on purchase quantities to ensure that more customers are able to purchase at least some of the supplies they need.

What's unclear is whether the impact on Costco's sales will be permanent or temporary. If customers are stocking up on things that they intend to use anyway, then Costco will presumably see less demand for those goods after the coronavirus crisis passes and consumers work through their stockpiles. Yet if the crisis inspires more customers to favor Costco over alternative outlets like grocery stores, then the boost to the warehouse club retailer's numbers could be longer-lasting.

Investors will get a better idea from the earnings release about how things went for Costco during the holiday season. However, it's tough to predict with certainty exactly how the coronavirus might help -- or hurt -- Costco both now and in the long run.

United slashes its schedule

Shares of United Airlines Holdings continued their recent skid, falling another 7% Thursday morning. The beleaguered airline said it would respond to the coronavirus outbreak with significant reductions in order to control costs as much as possible.

United said late yesterday that it would reduce U.S. and Canadian flight schedules by 10% in April and May. International flights would see a more dramatic reduction of about 20%.

The moves on flight schedules are only part of what United's doing to try to rein in expenses. The airline won't do any new hiring except to fill essential jobs, and it will defer planned merit-based increases to pay for its managers and administrative staff. To reduce compensation expense, United will also give U.S.-based employees the option to take unpaid leave on a voluntary basis.

Investors understand that the situation with the coronavirus outbreak is fluid, and so even measures like these might not be enough to protect United and other airlines from substantial losses. Nevertheless, with the outbreak representing the first major threat to the airline industry since it discovered its pathway to profitability more than a decade ago, investors will watch United and its peers closely to see whether their efforts work.