Dr. Scott Gottlieb told CNBC on Friday he believes the U.S. is significantly undercounting the number of Covid delta infections, making it difficult to know whether the highly transmissible strain is causing higher-than-expected hospitalization and death rates.
"We don't know what the denominator is right now," Gottlieb said in an interview on "Squawk Box." "I think we're vastly underestimating the level of delta spread right now because I think people who are vaccinated, who might develop some mild symptoms or might develop a breakthrough case, by and large are not going out and getting tested. If you've been vaccinated and you develop a mild cold right now, you don't think you have Covid."
Coronavirus cases in the U.S. have been rising due to the delta variant, with the seven-day average of new daily infections standing at 26,448, according to a CNBC analysis of Johns Hopkins University data. That's up 67% from a week ago. The weekly average of new daily deaths is up 26% from a week ago, to 273, according to CNBC's analysis.
"There's no clear evidence that this is more pathogenic, that it's causing more serious infections. It's clearly more virulent, it's clearly far more contagious" than earlier virus strains, said Gottlieb, who serves on the board of Covid vaccine maker Pfizer.