Steve Rusckowski, CEO of Quest Diagnostics, told CNBC on Thursday that the company is seeing a surge in Covid-19 testing as the more contagious Delta variant spreads across the country.

“We said that our Covid-19 testing business would decline as we would see the recovery from the pandemic, and it fell in the first half,” Rusckowski said on Closing Bell. “In the past few weeks, and we believe it is related to the Delta variant, we have also seen a slight increase in this Covid test volume.”

Rusckowski, who was CEO of Dutch healthcare technology company Philips Healthcare before joining Quest in 2012, said Quest is using next generation sequencing to provide Covid test results to centers for disease control and prevention. The majority of the positive tests the company identified this week were for the Delta variant, he said.

The highly communicable Delta strain is causing renewed spikes in cases and deaths in the United States, particularly in largely unvaccinated communities. This has raised concerns among health professionals and local officials across the country, some of whom have begun re-enacting and advising indoor mask requirements for both vaccinated and unvaccinated individuals.

More than 162 million people in the US are fully vaccinated – roughly 49% of the country’s population – although the rate of daily vaccinations continues to decline sharply, according to a CDC tracker.

While Rusckowski noted an increase in Covid tests, Dr. Scott Gottlieb told CNBC Thursday morning that while the current spike in Delta infections may be over sooner than expected, it’s hard to confirm as people are now being tested much less frequently than before.

“Vaccinated people do not present for testing, and many young and healthy people who are currently mostly infected do not present for testing,” said Gottlieb, a former head of the Food and Drug Administration.

As people return to in-person medical visits in the American healthcare system, Quest also posted unexpectedly high results in the second quarter, with business recovering in its non-Covid services such as cancer, cardiovascular and infectious disease testing, and neurology.

The New Jersey-based medical testing company reported adjusted earnings per share of $ 3.18 on sales of $ 2.55 billion. According to Refinitiv, analysts expected earnings per share of US $ 2.87 and sales of US $ 2.38 billion. Revenue was up 39.5% year over year when the company reported adjusted earnings per share of $ 1.42.

The company forecasts full-year sales between $ 9.54 billion and $ 9.79 billion.

“Our basic business declined significantly in April last year. Our basic business was not over 50% and we only started our Covid tests in March of last year, ”said Rusckowski. “Today we actually have around 300,000 test capacities per day. That was still zero in March of last year. So, in the second quarter of last year, our basic business was in decline and we’re just starting to ramp up our Covid tests. “