It's hard to swim against the current. But it's not impossible to do so.

Most stocks have fallen hard in the current market correction that was initially caused by worries about the coronavirus and is now being worsened by plunging oil prices. There are exceptions, though. Three profitable healthcare stocks have trounced the overall market indexes and could be poised to continue outperforming the market. Here's which stocks are swimming against the current -- and why they're winning.

$1 bill folded into an arrow that's pointing up

Image source: Getty Images.

1. Regeneron Pharmaceuticals

Shares of Regeneron Pharmaceuticals (NASDAQ:REGN) are up more than 20% over the past month, a period where the S&P 500 index tanked by 17%. Regeneron has defied stock market gravity thanks to three pieces of good news.

First, the biotech announced on Feb. 4 that it's working with the U.S. Department of Health and Human Services (HHS) to develop a treatment for the novel coronavirus. Regeneron already developed an antiviral drug for treating Ebola and has worked with HHS on developing a treatment for MERS, which is also a member of the coronavirus family.

Second, Regeneron announced better-than-expected fourth-quarter results two days later. Its eye-disease drug Eylea generated 11% year-over-year sales growth. Sales for cancer immunotherapy Libtayo more than quintupled compared to the prior-year period.

Third, Regeneron announced positive results on Feb. 8 from a late-stage clinical study evaluating Eylea in treating moderately severe to severe non-proliferative diabetic retinopathy (NPDR). Although this was the least of the catalysts boosting Regeneron's shares, the results could set the stage for the company to pick up another approved indication in the future for its blockbuster drug.

2. Gilead Sciences

Gilead Sciences (NASDAQ:GILD) stock is up around 5% over the last four weeks, a much better performance than the major market indexes. Like Regeneron, Gilead benefited from news about its antiviral program targeting COVID-19, the disease caused by the novel coronavirus.

There's a good reason to view Gilead as the leader in the coronavirus race. A World Health Organization (WHO) official stated in late February that Gilead's antiviral drug remdesivir is the "one drug right now that we think may have efficacy." Gilead has already started two late-stage clinical studies evaluating remdesivir in treating COVID-19. 

But its coronavirus program hasn't been the only news for Gilead in recent days. The company announced on March 2, that it plans to acquire clinical-stage biotech Forty Seven (NASDAQ:FTSV) for $4.9 billion. Forty Seven's lead candidate is experimental blood cancer drug magrolimab.

The purchase of Forty Seven fits perfectly with Gilead's strategy of making bolt-on acquisitions of small-to-medium-sized biotechs. And with Gilead Sciences CEO Daniel O'Day's background in oncology development, Gilead's scooping up of a cancer-focused small biotech like Forty Seven makes sense.

3. DexCom

It's not just big biotech stocks that are beating the market. Shares of DexCom (NASDAQ:DXCM) have jumped close to 10% over the last month. And the medical device company managed to achieve this gain without having any positive ties to coronavirus programs.

DexCom's shares are performing well because its business is performing well. The company announced good news across the board with its Q4 results. Revenue soared 37% year over year with continued momentum for DexCom's G6 continuous glucose monitoring (CGM) system. DexCom's adjusted earnings in Q4 blew past Wall Street estimates.

Some companies could experience a negative fallout from the coronavirus outbreak or from lower oil prices, but not DexCom. The medical device maker looks for a strong year in 2020 as its G6 CGM system gains momentum, especially in international markets.

DexCom also reported even more good news for its G6 CGM system on Feb. 19. The company is teaming up with Insulet (NASDAQ:PODD) to integrate the G6 CGM with Insulet's insulin pumps. DexCom and Insulet also agreed to integrate the not-yet-released G7 CGM system with Insulet's insulin pumps.

Continued momentum?

Regeneron, Gilead, and DexCom should be able to continue their momentum and keep outperforming the overall market. For Regeneron and Gilead, the primary catalyst is likely to be progress with their respective COVID-19 programs. For DexCom, it's all about the company's G6 CGM sales.

Over the long run, I like the prospects for Gilead and DexCom the most. Gilead could soon win approval for filgotinib, an immunology drug with huge sales potential. DexCom's rollout of the G7 CGM should keep the company at the forefront in diabetes management. The worries about the coronavirus will likely fade over time, but my view is that the opportunities for Gilead and DexCom won't.