On Jul. 11, 2025, in response to White House concerns about allegedly risky research on viruses, bacteria, and other pathogens, the National Institutes of Health (NIH) has begun a crackdown on dozens of studies it was funding, Science has learned.

Citing President Donald Trump’s executive order promising greater oversight of “gain-of-function” (GOF) research that’s potentially dangerous, the agency has demanded the scientists leading those studies suspend part or all of their work and propose modifications to their experiments that would limit any risk of creating more deadly or transmissible pathogens.

“NIH has identified 40 projects that may meet the definition of dangerous gain-of-function research. … Erring on the side of caution, all projects potentially meeting the definition are being suspended,” Matt Memoli, NIH’s deputy director, wrote in a 3 July draft letter to the White House describing NIH’s “interim response” to the executive order. The letter, obtained by Science, indicates an additional 172 projects have been flagged for potential suspension or termination.

Most of the suspended projects are taking place at U.S. universities, but nine are being conducted by NIH’s in-house scientists, according to a spreadsheet listing the 40 projects. That document also notes that those intramural investigators have already agreed to either stop or modify their research.

A dozen of the academic scientists on NIH’s suspensions list confirmed to Science that they had received notices from the agency but most did not want to comment on the matter. NIH’s selections have puzzled many infectious disease scientists and dismayed others. Nearly half involve tuberculosis (TB); studies on the mycobacterium that causes the disease have not traditionally sparked GOF concerns because an estimated one-fourth of the human population is infected with it and suffers no harm, the pathogen depends on prolonged exposure to spread, and TB is curable in most cases.

The studies targeted by NIH include both relatively low-risk, routine work and higher risk experimentation that is essential for developing new drugs and vaccines, several researchers told Science. JoAnne Flynn, a TB researcher at the University of Pittsburgh who is a co–principal investigator of one of the suspended grants, reviewed NIH’s list and called it “crazy” and “ridiculous.” Flynn’s own project involved using standard techniques to create mutants of Mycobacterium tuberculosis (Mtb) that are resistant to antibiotics. But she stresses that her work is not using any compounds that are currently recommended for TB treatment so she sees no risk of creating a dangerous strain capable of undermining those therapies. “This will really impede our understanding of Mtb infection,” Flynn says.

Concern about GOF research came to the fore in 2011 when two labs modified the deadly H5N1 bird flu virus to determine which mutations might allow it to better transmit between mammals. Federal officials in 2014 paused 18 projects before releasing 2017 guidelines that allowed work to move forward. But the debate flared again during the COVID-19 pandemic, when some scientists and Republican politicians, including Trump, alleged that the coronavirus responsible came from GOF work at a lab in Wuhan, China, that had received NIH funding.

Former President Joe Biden’s administration later revamped the U.S. government’s GOF policy, but Trump officials jettisoned that work with its executive order on 5 May. Some researchers criticized Trump’s order as vague and potentially so broad that it could derail relatively low-risk, promising research. NIH provided some follow-up guidance, but until now many infectious disease scientists were uncertain what work would be stopped by the agency.

Harvard University epidemiologist Marc Lipsitch, who has publicly called for stronger U.S. regulations on high-risk lab work that might accidentally trigger a pandemic, also questioned why NIH had suspended most of these projects. “Only a handful plausibly meet the standard in the executive order that they ‘could result in significant societal consequences,’” Lipsitch says. “While there are a few studies where I would want to learn more about the risks and benefits, I would predict that ending this list of studies, as a whole, will be detrimental to health security and public health.”