U.S. Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. is noted for his series of controversial claims, and some health experts believe this might be due to an obsolete medical theory he has promoted. Known as miasma theory, this belief system goes back centuries but has long been superseded by the basic theory of germs. However, some on the fringes of the medical community still promote it, which could be driving some of RFK Jr.’s more contentious HHS decisions.

What is miasma theory?

It is the disproven belief that diseases are “caused by inhaling air that was infected through exposure to corrupting matter,” according to the National Center for Biotechnology Information. It was believed this “bad air” could have been infected by “rotting corpses, the exhalations of other people already infected, sewage or even rotting vegetation.”

Miasma theory was one of the “first ideas that civilization hatched to try to explain why people get sick,” said NPR. It goes back to Hippocrates, who “wrote in a book called ‘Epidemics’ that epidemics came from some type of pollution — some pollution of the atmosphere,” Dr. Howard Markel, an emeritus professor of medical history at the University of Michigan, said to NPR.

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Germ theory was discovered in the last few centuries, though, revealing that it “wasn’t some mysterious stench in the air from rotting garbage that spread diseases,” said NPR. Instead, “bacteria and viruses and other microscopic materials were actually what caused illness,” Melanie Kiechle, a historian at Virginia Tech, said to NPR. Miasma theory is “debunked, essentially.”

Why is RFK Jr. a believer?

Kennedy “doesn’t believe in a foundational scientific principle: germ theory,” said Ars Technica. He wrote a section promoting miasma theory in his 2021 book, “The Real Anthony Fauci,” which criticized the former director of the National Institute of Allergy and Infectious Diseases. In the section, Kennedy “promotes the ‘miasma theory’ but gets the definition completely wrong.”

Kennedy’s book states that miasma theory “emphasizes preventing disease by fortifying the immune system through nutrition and by reducing exposures to environmental toxins and stresses,” according to Ars Technica. In Kennedy’s view, abandoning miasma theory led to a “pharmaceutical paradigm that emphasized targeting particular germs with specific drugs rather than fortifying the immune system.”

One of the main criticisms of Kennedy’s approach is that “miasma theory, as historians of medicine and science understand it, is not what [Kennedy] is saying it is,” Nancy Tomes, a historian of germ theory at Stony Brook University, said to NPR. This could lead to policy decisions coming as a result of miasma theory, which experts question. For Kennedy, vaccines are a “modern-day miasma,” Dr. Paul Offit, a vaccine expert at the University of Pennsylvania, said to NPR.

Kennedy’s “unscientific belief that germs don’t actually cause disease will likely have far worse consequences,” said Jalopnik. This is a “threat to modern medicine and health in this country, as well as across the world.” And many doctors believe this is all part of an effort to promote an anti-vax agenda. Kennedy is “trying to give this false veneer of intellectualism by saying, ‘Oh, the miasma theory,'” Dr. Amesh Adalja, a scholar at the Johns Hopkins Bloomberg School of Public Health Center for Health Security, said to NPR. This is “obfuscation to support his idea that vaccines are not valuable.”