One Health: New Term, Ancient Concept

In September 2001, I was entering the master’s degree program in public policy at Princeton University’s Woodrow Wilson School of Public and International Affairs. I had already earned MD and MPH degrees but felt that a policy degree would enable me to rise higher in government and have a greater influence on public health policy. I had been working in patient safety and hospital quality oversight at the New Jersey state health department. The work was important but hamstrung by politics.

My plans were turned upside down by the terrorist attacks of September 11, 2001 and the subsequent anthrax mailings in October of that year. I decided to dedicate my career to bioterrorism, emerging diseases, and emergency preparedness instead.

Putting the Pieces Together

The 1999 West Nile virus outbreak was also uppermost in my mind. That crisis was notable because two outbreaks had occurred: one in animals and one in humans. In May 1999, crows began displaying unusual behavior and dying by the thousands in Queens, a borough of New York City. Two months later, people began being hospitalized with neurologic signs and symptoms suggestive of St. Louis encephalitis (SLE), a deadly mosquito-borne disease.

But the pieces weren’t adding up. Dr. Tracey McNamara, chief of veterinary pathology at the Bronx Zoo, played a key role in identifying the causative agent. She knew something wasn’t right because the European and African birds that should have been getting sick from SLE were healthy while the birds native to North America were dying. She and her staff performed necropsies in a number of zoo birds and found massive cardiac necrosis, horrific meningoencephalitis, and liver coagulative necrosis. She knew the causative agent wasn’t SLE, but the public health community wasn’t interested in her findings because they were in animals. They didn’t listen to her because she was a veterinarian. In the end though, she was right. West Nile virus had appeared for the first time in North America.

I discovered in my research that the medical and veterinary medical communities rarely, if ever, talk with each other even though around 60% of human pathogens and 75% of newly emerging pathogens are zoonotic. The vast majority of bioterrorism agents are zoonotic too. This is not news for the veterinarians who have taught me much about microbial ecology.

Communication and Collaboration Are Key

They’ve also taught me about comparative medicine: the study of disease processes across species. Animals suffer from many of the same diseases as humans—heart disease, cancer, diabetes, and so on. Many of these disease processes are similar across species. We could learn a tremendous amount if only we communicate and collaborate with each other. This is where "One Health" can play an important role.

The One Health concept is simply that human, animal, and environmental health are linked. Because they are linked, complex subjects such as emerging diseases and antimicrobial resistance must be examined using an interdisciplinary, holistic approach. The term “One Health” is relatively new, but the concept is ancient. The Greek physician Hippocrates (460—370 BC) recognized that people who went to low-lying swampy areas often got sick. The term “malaria” literally means “bad air.” Over 2000 years would pass before people figured out that insects, such as mosquitoes, could transmit disease.

Some of the greatest discoveries in the history of medicine and public health were made at the human—animal interface. Dr. Edward Jenner coined the term “vaccination” from the Latin word “vacca” for cow. He used cowpox pus instead of smallpox pus during “variolation,” an ancient process developed in China or India by which small bits of dried pus from someone recovering from smallpox were scratched into the skin of a naïve person (usually a child) as a way to reduce smallpox mortality from more than 30% to less than 5%. A purified version of the vaccine was used to eradicate smallpox several centuries later.

Drs. Louis Pasteur and Robert Koch independently discovered the germ theory of disease by studying animal diseases. Drs. Theobald Smith and F.L. Kilbourne, a physician—veterinarian team, discovered that ticks could transmit disease, in this case, cattle fever, caused by the parasite Babesia bigemina. The discovery that insects could spread disease was a monumental finding and helped set the stage for Dr. Walter Reed and his colleagues to prove that mosquitoes could transmit yellow fever.

To fill the communications gap between physicians and veterinarians, my colleagues and I cofounded the One Health Initiative. The One Health Initiative website has been serving as a global repository for all news and information pertaining to One Health since 2008. Please visit it. We look forward to any feedback that you might have.

[This article originally appeared online at MD Magazine.]

Dr. Kahn is a physician and research scholar with the Program on Science and Global Security at the Woodrow Wilson School of Public and International Affairs, Princeton University. In April 2006, she published the article “Confronting Zoonoses, Linking Human and Veterinary Medicine” in Emerging Infectious Diseases, which helped launch the One Health Initiative. She is also the author of Who’s in Charge? Leadership during Epidemics, Bioterror Attacks, and Other Public Health Crises (2009) and One Health and the Politics of Antimicrobial Resistance (2016).