Why Do Contagious Diseases Evade Eradication?

From the Plague of Athens, Greece more than 2,500 years ago, to the modern COVID-19 pandemic, humankind has long struggled against microbes that sicken, disable and kill their way through society.

In a recent lecture, a top infectious disease expert and medical historian from the University of Michigan surveyed this legacy of contagion and the lessons that past epidemics and pandemics can teach us.

Powel Kazanjian, M.D., Ph.D., chief of infectious diseases in the Michigan Medicine department of internal medicine, gave the talk through the U-M Center for the History of Medicine. "Our experience for the current pandemic seems unprecedented, but history is a good way to provide some perspective for us, and some guidance," he said.

In the centuries before modern scientific methods began to take hold, Kazanjian says, infectious diseases were thought to be caused by imbalances of the body's "humors" of blood, phlegm, black bile and yellow bile, and by sinful behavior associated with shame and stigma.

Scientific methods developed since the Renaissance have given us an ever-growing understanding of what causes diseases, and how to stop infectious ones from spreading. In the past 125 years, that understanding has made it possible to detect specific infectious bacteria, viruses and other microbes, and develop tests and treatments for them.

But as he describes in the lecture, this knowledge alone has not been enough to defeat diseases such as syphilis, HIV/AIDS and now, the novel coronavirus.

"Biomedicine is very powerful and by itself it tends to create advances in permissive political times," he says. "But it must be accompanied by attempts to ameliorate and rectify social problems and political issues. It's not enough to interrupt the spread of the pathogen – you must also pay attention to those broader environmental issue that create a susceptible environment" for the disease's transmission.

Kazanjian has studied the history of efforts to stop syphilis, which accelerated in the 20th Century once microscopes allowed its cause to be discovered. Soon after, scientific research led to the development of a test to confirm cases, and treatments to stop it from disfiguring and disabling its victims.

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He says that the use of shaming and moralistic messaging, and the lack of focused efforts to reach people most at risk of catching and transmitting the microorganism that causes the disease, have doomed decades of repeated efforts to wipe syphilis out in the United States.

Today, there are more cases than ever. But new efforts to address the social factors that create the conditions needed for infections have begun.

Kazanjian, whose medical career began just as the AIDS crisis began in the early 1980s, knows well the history of the political, activist and scientific efforts to fight that disease in the U.S. and developing nations.

Today, much progress has been made in getting the antiretroviral drugs developed by scientific progress to tens of millions of people as treatment or pre-exposure prevention.

But cost and social barriers, including poverty that forces people into sex work, lack of treatment in rural areas, and lack of needle exchange programs for intravenous drug users, stand in the way of eradicating AIDS worldwide.

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The political environment for the COVID-19 pandemic is having an even greater impact on the ability to bring the disease under control, especially in the U.S., he says.

Misinformation and denial of scientific recommendations have created a narrative that has galvanized people to feel righteous in disavowing scientists' recommendations, Kazanjian notes.

Even though rapid scientific progress has led to the development of vaccines and monoclonal antibodies, the political and social environment surrounding the current pandemic threaten the trust needed to ensure broad vaccination of the American population.

"We have to address the poverty and the mistrust that people have in government and science," in order to bring the current pandemic to an end, and fight future ones, he says. "Epidemics are going to be part of our existence."

Papers cited:

"UNAIDS 90-90-90 Campaign to End the AIDS Epidemic in Historic Perspective," Milbank Quarterly. DOI:10.1111/1468-0009.12265

"Ebola in Antiquity?," Clin Infect Dis. DOI: 10.1093/cid/civ418