Florida, Texas, Arizona and other states seeing major spikes in new coronavirus cases are heading into a "pivotal week" that might determine whether "they're tipping over into exponential growth or not," former Food and Drug Administration Commissioner Dr. Scott Gottlieb told CNBC on Monday.
A number of states, mostly across the American South and West, have seen a dramatic rise in cases over the past couple of weeks as more people move about in increasingly reopened areas and the virus spreads to new communities.
"I think this week's going to really be a pivotal week for us to get a picture of where things are heading in states like Florida and Arizona and Texas, whether or not they're tipping over into exponential growth or not," Gottlieb said on CNBC's "Squawk Box." "The problem is with exponential growth everything looks sort of OK until all of a sudden it doesn't."
Officials in some states, including Florida, initially pointed to increased testing as a driver of the spike in new confirmed cases. However, Florida Gov. Ron DeSantis acknowledged that the share of people who test positive is accelerating faster than the number of tests being run. The percentage of people testing positive for the virus in Florida has risen from about 4.2% on June 7 to more than 8% on June 14, the most recent data available, according to the Florida Department of Health.
The positivity rate has similarly risen in Arizona, which has been reporting more than 2,000 new cases per day for about a week. The statistics to watch this week will be the doubling rate of the outbreaks in such states, Gottlieb said.
"That's going to be a curve that's starting to look like exponential growth, the doubling time coming down to something about a week or less," he said. "Right now, the doubling time is about 10 days in some of these places, so it's been coming down."
The number of deaths due to Covid-19 does not appear to be rising along with the number of confirmed cases, Gottlieb said. However, that could be due to the lag in time it takes for infected people to fall ill, become hospitalized and then die. Gottlieb said he doesn't think the death rate will rise drastically, as doctors have become better at treating patients and more people who get infected are younger and not as vulnerable as the elderly or those with underlying health conditions.
Nonetheless, if such states fail to bring down the rate of spread and contain the virus, Gottlieb said, it will find its way to at-risk communities. The longer officials in these states allow the virus to spread, he said, the more difficult it will be to bring it under control.
"They're having major outbreaks underway. There's no question about it," he said. "They might be past the point that they can control this just with simple interventions like trying to get more people to wear masks and people being mindful of their social interactions."
States with the worst outbreaks might have to start closing businesses down again, Gottlieb said, adding that it would be best if officials could target establishments where they know people are congregating and getting infected. DeSantis of Florida and Texas Gov. Greg Abbott have both attributed part of the rise in cases to young people disregarding precautions, especially at bars.
"They're guessing it's the bars because a lot of young people are getting the illness, but I don't think they've really traced it back to those locations effectively," Gottlieb said, "because they don't have the tracking and tracing in place that other states, including New York, New Jersey and Connecticut, had as they reopened."
Tracing occurs when health officials contact infected people to try to understand how they might have become infected and who they might have exposed to the virus before they were diagnosed. It's an age-old, proven public health strategy that's used to combat infectious diseases like measles and tuberculosis.
Establishing strong contact tracing infrastructure was part of the White House's reopening guidelines, though it was not required nationally in order to ease restrictions and reopen businesses. And rather than taking a leadership role, the Centers for Disease Control and Prevention has instead sought largely to support local health departments as they try to ramp up tracing systems.
"They might have to start closing some establishments where people are congregating indoors and they know the virus is spreading," Gottlieb said of cities with major spikes. "The problem is they don't know what those establishments are."
The Northeast, especially the New York City metro area, was once the epicenter of the U.S. outbreak, but has since seen cases drop sharply as other states continue to report record spikes. New York City is moving Monday into its next phase of reopening, which will allow for hair salons, outdoor dining and more.
"We'll see an increase in cases, but we're reopening against a much different backdrop," Gottlieb said. "So I wouldn't expect to see the big increases that they're seeing in the Southeast and the South here when we reopen."
New York, New Jersey and Connecticut all drove daily new infections way down before reopening at all, Gottlieb said, noting that states now seeing a spike reopened early while they still had considerable spread in some communities. He added that people in the Northeast, many of whom saw some of the worst of the outbreak, are more likely to adhere to public health guidance like mask wearing and social distancing.
He added that because the virus infected so many people in the Northeast, a greater portion of the population likely has some degree of immunity or resistance to infection.
"New York probably 30% of the population's been infected. In New Jersey and Connecticut, probably around 10% if you did seroprevalence studies, maybe higher than that," he said. "There's been more infection here, so the transmission rate's going to be a little bit less because of that."
Disclosure: Scott Gottlieb is a CNBC contributor and is a member of the boards of Pfizer, genetic-testing start-up Tempus and biotech company Illumina.