We have each had the honor and privilege of serving as director of the Centers for Disease Control and Prevention, either in a permanent or acting capacity, dating back to 1977. Collectively, we spent more than 100 years working at the C.D.C., the world’s pre-eminent public health agency. We served under multiple Republican and Democratic administrations — every president from Jimmy Carter to Donald Trump — alongside thousands of dedicated staff members who shared our commitment to saving lives and improving health.

What Health and Human Services Secretary Robert F. Kennedy Jr. has done to the C.D.C. and to our nation’s public health system over the past several months — culminating in his decision to fire Dr. Susan Monarez as C.D.C. director days ago — is unlike anything we have ever seen at the agency, and unlike anything our country has ever experienced.

Secretary Kennedy has fired thousands of federal health workers and severely weakened programs designed to protect Americans from cancer, heart attacks, strokes, lead poisoning, injury, violence and more. Amid the largest measles outbreak in the United States in a generation, he’s focused on unproven “treatments” while downplaying vaccines. He canceled investments in promising medical research that will leave us ill prepared for future health emergencies. He replaced experts on federal health advisory committees with unqualified individuals who share his dangerous and unscientific views. He announced the end of U.S. support for global vaccination programs that protect millions of children and keep Americans safe, citing flawed research and making inaccurate statements. And he championed federal legislation that will cause millions of people with health insurance through Medicaid to lose their coverage. Firing Dr. Monarez — which led to the resignations of top C.D.C. officials — adds considerable fuel to this raging fire.

We are worried about the wide-ranging impact that all these decisions will have on America’s health security. Residents of rural communities and people with disabilities will have even more limited access to health care. Families with low incomes who rely most heavily on community health clinics and support from state and local health departments will have fewer resources available to them. Children risk losing access to lifesaving vaccines because of the cost.

This is unacceptable, and it should alarm every American, regardless of political leanings.