Employing a distinct shift in tone from a prior press briefing on Tuesday, a director at the Centers for Disease Control and Prevention praised President Donald Trump's containment strategy and avoided using any language that would trigger concern over what some health experts are calling a global pandemic.

“We need to remember that the case count is really low and that is a reflection of the aggressive containment measures of the U.S. government," said Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, during a telephone press briefing on COVID-19, the World Health Organization's official name for the current coronavirus disease.

The briefing capped off a whirlwind week for the federal health agency and Messonnier, who found herself the target of right-wing attacks after she delivered the most sobering warning to date about the coronavirus epidemic.

On Tuesday, Messonnier, a 25-year veteran of the agency, described the coronavirus as nearing closer to a pandemic, and said the spread of the coronavirus in the U.S. would be inevitable, a potential that Trump has sought to downplay.

"Ultimately, we expect we will see community spread in this country," she said, referring to cases in which the source of infection is unknown. California currently has one such case.

Messonnier continued: "It’s not so much a question of if this will happen any more but rather more a question of exactly when this will happen and how many people in this country will have severe illness."

“We are asking the American public to prepare for the expectation that this might be bad," she added.

She said the agency was "operationalizing all of its pandemic response plans."

After her statements, the U.S. stock market tumbled for the second day in row. The following day, Rush Limbaugh, the conservative talk radio host and Trump backer, suggested that Messonnier was biased because she is the sister of Rod Rosenstein, the former deputy attorney general who angered the president over his oversight of the Robert Mueller investigation. His opinion has fueled conspiracies on Twitter.

President Trump on Wednesday placed Vice President Pence in charge of the task force responding to coronavirus. According to the NY Times, the White House has since been working to "tighten control of coronavirus messaging" and directed scientists and health officials to coordinate all statements and public appearances with Pence.

Friday's press briefing reflected a more positive embrace of the president that was in line with White House talking points. "As always, President Trump and our administration's number one priority is the health and safety of the American people," Messonnier said at one point.

The statement was nearly identical to one used by Pence on Fox News Thursday.

In contrast to previous press briefings, Messonnier seemed to take pains to credit the administration. “Because of the aggressive U.S. effort, border strategy and containment strategy, the number of cases is low," she said.

Then later: “The U.S. acted incredibly quickly before other countries. We aggressively controlled our borders.”

However, a government whistleblower has reportedly told Congress that a team of federal health employees improperly interacted with Americans quarantined for possible exposure to the coronavirus without medical training or protective gear. In the aftermath, they made the broader population vulnerable to infection.

Dr. Irwin Redlener, the director of Columbia University's National Center for Disaster Preparedness, criticized the administration's attempt to muzzle the CDC, calling it unprecedented and "entirely inappropriate."

Many health experts have called on the CDC to hold daily briefings in light of the quickening spread of the coronavirus outside of China.

Asked how often the agency planned to brief the public, Messonnier was notably vague, saying, "We will continue to routinely provide telebriefings to provide updated information when we can."

The story has been corrected to say that Messonnier said the coronavirus was nearing closer to a pandemic. She did not say it was currently a pandemic.