Dr. Scott Gottlieb explained why he’s optimistic about Merck‘s Covid antiviral pill after the drugmaker asked the Food and Drug Administration Monday to authorize its pill to treat people with mild to moderate Covid symptoms. 

“The topline data from this Merck study was probably the best treatment effect we’ve seen from orally available antiviral drug in the treatment of any respiratory pathogen, so this can make a real difference,” said the former FDA chief in the Trump administration. 

If the agency signs off on the drug, it will be the first pill shown to work against Covid-19 and Americans could get it by the end of the year. 

Gottlieb told CNBC’s “The News with Shepard Smith” Merck’s pill is part of an “overall, significant improvement in our therapeutic toolbox against this virus, not just with vaccines and therapeutics, but also with more accessible diagnostic tests.”

Host Shepard Smith also asked Gottlieb about masking rules across the country. Gottlieb told Smith that he thinks decisions will be made at a local level and noted the varying prevalence of the delta variant across the U.S. 

“We’ve seen sharp declines in the south, where delta’s largely run its course, so cases are coming down very sharply in populous states like Texas and Florida, but you’re seeing pretty dense epidemics in the midwest and plain states, and we still don’t know how the northeast and the northern states are going to fare,” Gottlieb said. 

He predicted that a Covid-19 delta wave could hit northern U.S. states, despite higher vaccination rates and higher prior infection rates. 

“I still think that there’s a delta wave that’s going to sweep across the northern states, as well in the northeast, it’s not going to be nearly as dense as what you saw in the south, but we still are probably in store for more spread,” Gottlieb said.

Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic testing start-up Tempus, health-care tech company Aetion Inc. and biotech company Illumina. He also serves as co-chair of Norwegian Cruise Line Holdings’ and Royal Caribbean’s “Healthy Sail Panel.”