As the U.S. prepares to reopen during the pandemic, authorities should be ready to retrace their steps if easing of social distancing measures don't work — otherwise, they could be right where they started, warned the former director of the Centers for Disease Control and Prevention.
Another concern for her is that "superbug" infections — which are resistant to antibiotics — could lead to more deaths, said Julie Gerberding, who was director of the CDC from 2002 to 2009.
"If we're going to take a step toward loosening some social distancing requirements, then we need to observe what happens, and if that seems to go okay we can take the next step. But if we see things happen in the wrong direction, we have to be prepared to go back a step," she told CNBC's "Squawk Box Asia" on Wednesday.
The vast majority of Americans have not been exposed to the coronavirus and have absolutely no immunity to it, she said. That leaves "most of the country vulnerable," said Gerberding, who is currently executive vice president and chief patient officer at Merck.
"I think what we've proven is that the social distancing measures that have been recommended actually work, but when you pull back from those, you can only expect that there are going to be hotspots just like Dr. Fauci described."
Dr. Anthony Fauci, the top infectious disease expert in the U.S. and a White House health advisor, on Tuesday testified before the Senate committee on the administration's response to the coronavirus crisis. He warned of serious consequences if states reopened too quickly, and highlighted his concerns that "little spikes" could possibly turn into outbreaks.
"If those hotspots get out of control without the surround sound of the right testing and the contact tracing, we're right back where we started — or worse," warned Gerberding.
As of Thursday morning Asia time, the number of reported coronavirus infections in the U.S. topped 1.3 million, with more than 84,000 people killed, according to Johns Hopkins University data.
Gerberding warned of another "hidden danger" of the coronavirus — "superbugs." They are germs that have adapted and become resistant to different types of antibiotics used to treat the infections they cause.
Secondary superbug infections can creep in among those who are very sick and have been hospitalized for a long time, and infect patients who are already undergoing invasive procedures such as ventilators and catheters, she said.
"In fact about 1 in 7 hospitalized coronavirus patients seem to develop a secondary bacterial infection," she said.
While superbugs can be eradicated with complex antibiotics, the medication is running short because the bacteria or viruses are becoming more resistant faster than the drugs can be developed, Gerberding said.
In addition, many hospitals do not carry these expensive antibiotics, and the reimbursements systems don't work out to provide appropriate and fair compensation, she added.
According to a study by the Lancet medical journal, doctors conducted research on more than 190 patients with Covid-19 at two Wuhan hospitals, and found that half of those who died experienced a secondary infection. Wuhan is the epicenter of China's outbreak and the city where the virus is believed to have first emerged.
"I'm very concerned about the number of people who are going to lose their lives — not because of coronavirus but because of these deadly, super infections," she said.