As fears grow about the spread of the coronavirus within the United States, right-wing media figures are going after a top CDC official with ties to Philadelphia.

For the past 25 years, Dr. Nancy Messonnier has worked for the Centers for Disease Control and Prevention, where she has taken a leading role in warning the public about the potential spread of the coronavirus. On Tuesday, Messonnier, a Philadelphia native and University of Pennsylvania graduate, warned that an outbreak with the United States appears inevitable.

“It’s not a question of if but rather a question of when and how many people in this country will have severe illness," Messonnier told reporters, warning if the virus spreads widely, drastic methods might be required to contain it, such as closing schools and requiring employees to work from home.

“The disruption to everyday life might be severe," she warned.

» READ MORE: Coronavirus will spread in the U.S., CDC warns, and there might not be enough testing capacity to detect it

But some right-wing media figures aligned with President Donald Trump — including popular radio host and Presidential Medal of Freedom recipient Rush Limbaugh — want listeners and readers to ignore Messonnier’s extensive background and knowledge of infectious diseases in favor of a baseless conspiracy theory that she is secretly working to harm Trump and his administration.

Their evidence? Her brother happens to be Rod Rosenstein, Trump’s former deputy attorney general who was responsible for appointing Robert Mueller as special counsel to investigate Russia’s interference in the 2016 presidential election.

» READ MORE: Rod Rosenstein: The one man standing in Trump's way is the president's polar opposite

On his nationally syndicated radio show Wednesday, Limbaugh took issue with Messonnier for warning about the likely spread of coronavirus within the United States, suggesting her real goal was to create panic and tank the stock market, thereby hurting Trump’s chances of being reelected:

Dr. Nancy Messonnier of the Centers for Disease Control — which today warned it could be bad, it might be bad, don’t go to school and don’t go to work, stay home and teleconference — is the sister of the former deputy attorney general, Rod Rosenstein. Well... do what you want with it. It may mean nothing. Who knows? It’s just in that town, I’m telling you, everything is incestuous. Most of that town is establishment oriented or rooted, which means they despise Trump.

The CDC did not immediately respond to a request for comment.

“The consequences of Limbaugh’s actions could be life or death. If the coronavirus does begin to spread within the United States, the public will have to rely on experts like Messonnier,” wrote Judd Legum, who covers conservative media on his Popular Information newsletter. “If Limbaugh’s 20 million listeners choose […] his conspiracy theories instead, they could put themselves and their families in danger.”

The baseless conspiracy theory began in the fringes of right-wing media, where it was mentioned on Twitter before being picked up on fringe, pro-Trump websites. Gateway Pundit, a right-wing conspiracy theory site that has received White House press credentials from the Trump administration, pointed to the fact that Messonnier briefed reporters while Trump was in India as proof of her desire to harm the president.

Trump himself appears focused on the coronavirus’ impact on the stock market, saying at a news conference Wednesday night “the risk to the American people remains very low” and “I don’t think it’s inevitable.” The Washington Post reported that the president was “furious about the stock market’s slide,” and CNBC Washington correspondent Eamon Javers reported Trump was also upset about Messonnier’s comments.

Conspiracy theories about the coronavirus have also spread to mainstream news organizations. Fox News programs have repeatedly promoted a debunked theory that the coronavirus was developed in a lab Wuhan, China, as part of the country’s biological weapons program. Sen. Tom Cotton (R., Ark.) has also pushed the false theory multiple times, including during a Senate Armed Services Committee hearing.

“Based on the virus genome and properties there is no indication whatsoever that it was an engineered virus,” Richard Ebright, a professor of chemical biology at Rutgers University, told the Washington Post.

There have been 60 confirmed cases of coronavirus within the United States, most of whom caught it overseas, according to a dashboard created by Johns Hopkins University’s Whiting School of Engineering. Globally, more than 82,000 people have contracted the disease, which has killed at least 2,800.

» For more on the coronavirus in the Philadelphia area, check here for latest updates.