The coronavirus pandemic has significantly altered consumer behavior this year. From loading up on toilet paper and hand sanitizer to doing more online shopping, people in 2020 have focused more on day-to-day essentials while also making the most of technology.

For some businesses, demand for their products and services has skyrocketed this year. Telehealth giant Teladoc (TDOC 3.31%) is experiencing significant growth in 2020 and its shares are up 164% year to date, outperforming the S&P 500 and its 4% returns by a wide margin.

However, as more of normal life returns, the trends that lifted stocks like Teladoc this year will start to subside. And that's what's happening now. Here are two trends that are beginning to die down.

1. Consumers loading up on staples

One consumer goods company that's generated better-than-normal sales growth this year is Campbell Soup (CPB -0.35%). As people worried about prolonged stays at home during the pandemic, they've been stocking up on pantry items, like the company's popular canned soup products. But that's starting to slow a little bit, especially as restaurants are now open and people are eating out (or ordering takeout) more. When the New Jersey-based company reported its fourth-quarter earnings report on Sept. 3, for the period ending Aug. 2, its sales were $2.1 billion and organic net sales growth was 12%. That's down from the previous period, when Campbell's organic net sales were up 17% for the quarter ending April 26.

A woman wearing headphones and a surgical masks gazes out the window of a house.

Image source: Getty Images.

That's still significantly better than the 1% organic growth Campbell's reported on March 4 with its second-quarter results, which were for the period that ended Jan. 26, just before COVID-19 began affecting sales. The company's CEO Mark Clouse knows this recent growth isn't sustainable, saying "this window is so unique, we've got to make the most of it." He sees this as an opportunity to try and retain customers, so that once this phase of stockpiling day-to-day products ends, these consumers will still buy his company's products.

But if there's a second wave of COVID-19 that sends consumers back into a panic, Campbell's could see another spike in its sales. However, this is not something investors should count on, and it would be risky to invest based on that assumption.

Despite the strong sales year Campbell's is enjoying in 2020, its shares are still down 1% year to date.

2. Patients choosing telehealth over in-person doctor visits

Another trend that was likely to change as pandemic restrictions eased was the number of people making virtual telehealth visits. While a platform like Teladoc's is convenient and easy to use, many people still prefer to see their doctors in person.

Data from the Epic Health Research Network shows that in April, telehealth visits made up 69% of total healthcare visits. But, steadily, more people have been visiting their doctors' offices. By July, telehealth's share of medical visits declined to 21%. This is still a large increase from before the pandemic, when telehealth accounted for less than 1% of all visits.

Investors will see a gauge of how strong the telehealth industry is when Teladoc reports its third-quarter results in the weeks ahead. In its second-quarter results, released July 29, Teladoc reported 2.8 million visits for the period ending June 30. That was three times the level of visits the New York-based company recorded during the same period a year ago. In the first quarter, for the period ending March 31, Teladoc had already hit two million virtual visits, which was up 92% year over year. Teladoc is projecting a modest slowdown for the third quarter, expecting virtual visits to total between 2.5 million and 2.7 million.

But Teladoc may do better than other telehealth providers, even if patients are making more in-person trips. In August, the company announced it would be merging with Livongo Health (LVGO), which helps patients with chronic conditions, including diabetes; Livongo helps them stay on top of their glucose readings, and to share that information with health coaches and doctors. The $18.5 billion deal will unlock significant opportunities for Teladoc, as there's only a 25% overlap in customers between the two companies. Teladoc expects the deal to close before the end of the year.

Avoid buying stocks based on short-term trends

It's risky to buy stocks based on trends that may not last. While the COVID-19 pandemic may not be going away anytime soon, that doesn't mean that trends from its early stages will continue for the long term. At some point, pantry space will run out, and consumers simply won't be able to load up on canned goods the way they did earlier in the year.

That's why a stock like Campbell's isn't doing terribly well this year, down 2% thus far: The boost it's gotten in sales due to the pandemic won't be sustainable over the long term.

Telehealth is much more likely to continue growing, given that it's a new service patients can keep using. But that's also a risk -- because there's no baseline investors can compare numbers to. Before COVID-19, telehealth wasn't much of a consideration for many patients; now, as more health insurers and employers cover it, it's likely to be an option that's here to stay. But what percentage of healthcare visits will be made via telehealth as concerns surrounding COVID-19 ease?

Teladoc's business isn't profitable, and may not be for some time as the company continues to grow. Meanwhile, investors are paying 21 times Teladoc's trailing-12-month revenue to buy its shares, well above the industry average price-to-sales ratio of about 1.7. If you're paying that kind of a premium for a stock, you should be fairly confident about its future growth prospects.

As you examine businesses that are doing better than normal amid the pandemic, exercise extra caution. The trends giving them a boost may not last -- or at the very least, may have a lesser impact over the long term.