We live in a world where the processes of continuous implementation of innovative ideas are normal and do not attract attention. We expect an endless stream of new and better things to accelerate growth, development and prosperity. But it was not always so. From the very beginning of history until about the 19th century, everyone was farmers on the brink of survival, everyone was poor, and the income growth of the average resident was zero. An innovative economy is rather an exception in human history. And the fight against infectious diseases paved the way for this exclusion.
Innovation occurs when large numbers of people gather in close proximity and share their ideas and insights with each other. Innovation requires personal contact and social connections. The dependence of innovation on the density of social interaction can be accurately described in simple equations - the same ones that show how infectious diseases spread.
Like innovation, some diseases shape the development of entire societies and cultures, setting opportunities and constraints. Disease not only causes suffering, it can destroy innovation, civilizations, and even entire species.
It should come as no surprise to us that communicable disease control has played an important role in the development of our ever-changing world. Prior to the emergence of such control, the necessary concentration of minds entailed the spread of diseases, which hit innovative development.
The population of the largest cities in the enlightened world in 1800 was only a few hundred thousand people. Residents died faster than new citizens were born, and even such modest population indicators were maintained only thanks to the constant influx of migrants from rural areas.
Of all the diseases that devastated growing cities, the worst was tuberculosis. "Desolation" - that's putting it mildly: every tenth died. Tuberculosis accounted for a quarter of all urban deaths in Europe and North America in the early 19th century. 80% of those infected died. Like AIDS today, the devastating impact of tuberculosis was due to the fact that the victims were mostly young people - the most dynamic, productive and innovative members of society. It is because of tuberculosis that the theme of orphans and orphanages arises in many Georgian and Victorian novels.
The golden age of public health from roughly 1860 to 1960 overlaps with the golden age of innovation, and this is no coincidence. Clean water, food, and vaccines have made dense cities livable, driving innovation and creativity to unprecedented levels. The sharp decline in infant mortality has spared women the burden of having to give birth and nursing a lot during endless medical crises. The answer was the desire of women to receive education and participate in public life. This has never happened before in the history of mankind.
The proportion of deaths from tuberculosis, as well as from other infectious diseases, has dropped significantly. In England and Wales, the number of victims of infections between 1860 and 1950 fell by almost 90%, in other industrialized countries the statistics were similar. And this decline preceded the moment when antibiotics became generally available. It can be safely attributed to public health measures, primarily the availability of clean water and food, and the development of vaccines. We know how to prevent the spread of infectious diseases, and this is a comforting thought in a world where antibiotics are beginning to lose their invulnerability.
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But there is one caveat to this good story: we do not know why TB has receded. In part, this can be attributed to the pasteurization of milk, through which the bovine form of tuberculosis was spread. Tuberculosis is not foodborne, so sanitation of slaughterhouses and the development of refrigeration systems have not been affected. Unlike yellow fever or malaria, tuberculosis is not transmitted by insects, so it could not be stopped by draining the swamps. Water purification prevents diarrheal diseases that have killed many children, but does not interfere with the spread of TB, which is transmitted from person to person. Vaccines have stopped killer diseases such as diphtheria and smallpox, but the tuberculosis vaccine is not very effective.
Medical historians have put forward other theories. After the German doctor Robert Koch established the infectious nature of tuberculosis in 1882, isolation wards and sanatoriums began to be created to interrupt the chain of transmission of the disease. But such attempts were inconsistent and sporadic, and many scientists doubt that they have played more than a minimal role in the fight against tuberculosis. Since the mortality rate from this disease was very high for a long time, it was also suggested that the mechanisms of natural selection and the formation of innate immunity influenced the decrease in the incidence. A number of pieces of evidence support this hypothesis.
British physician and medical historian Thomas McKeown was skeptical about this explanation. In the 1960s and 1970s, he published a series of works in which he argued that tuberculosis, in principle, and perhaps completely, is a social disease that responded not to measures in the field of medicine and health, but to improve people's living conditions. McKeon pointed out that the decline in the incidence of tuberculosis began earlier than other communicable diseases, and the rate of this decline was closely intertwined with measures to improve social well-being, rather than the introduction of various public health methods and new medical interventions. Despite his professional training, McKeon became a kind of nihilist from medicine, claiming that remedial measures are pointless, and remediesfunding for research and development by the British National Health Service would be better spent on food and housing for the poor.
There is an intuitive appeal in McKeon's thesis. In rich countries, tuberculosis has almost disappeared and is considered a disease of the poor. But subsequent research, based on more sophisticated analyzes of demographic and economic data, did not support McKeon's claims, and his claims are now largely overturned. However, no other explanation has received widespread support.
In the late 1940s, it seemed that the advent of antibiotics for the treatment of tuberculosis made all this reasoning irrelevant and uninteresting to anyone other than medical historians. For the first time, tuberculosis could be treated with steptomycin, isoniazid, rifampin. The chain of transmission could be disrupted without placing patients in isolation wards. There was no longer a need to tackle the daunting task of providing the world's poor with decent food and housing. Antibiotics were cheap and effective. If they could be given to every patient, the tuberculosis threat to human health and civilization would remain in the past, and probably forever.
Thus, the emergence of antibiotic-resistant tuberculosis has become a special threat, unlike the threat from the so-called superbugs and much more serious. Most MDR bacteria are characterized by reduced virulence - the ability to spread and cause disease in the host organism.
They rarely affect otherwise healthy people. For most pathogens - methicillin-resistant Staphylococcus aureus, carbapenem-resistant enterococcus, vancomycin-resistant enterococcus, extended-spectrum beta-lactamase - advanced age, hospitalization, immunosuppression and recent antibiotic use are risk factors for serious infections and death. They attack the old and the sick, not the young and healthy.
This is not the case with multidrug-resistant tuberculosis, and acquiring this trait does not make the disease less contagious. The age of the majority of patients is from 25 to 45 years, that is, they are in their prime. The main risk factors are anti-tuberculosis therapy in the past and refugee status. Multidrug-resistant TB is treatable, but difficult, costly and often ineffective. In 2015, half a million people fell ill with such tuberculosis, and only a quarter of them received adequate treatment and are recovering.
Most organisms become less virulent as they spread, but it is possible that multidrug-resistant tuberculosis is even more infectious in densely populated areas. If this is true, then we have big problems. We do not have a reliable plan B for an outbreak of drug-resistant virulent strains. Millions of sick people cannot be isolated. Improving sanitation will not help as the disease spreads from person to person by coughing, sneezing, and even talking. Natural selection may have made us less susceptible to infection than our ancestors, but this is only hope, not a plan.
At some point, tuberculosis can shake our progressive innovative society.
The interplay of “producers” we trust to manage our economy will help spread deadly, difficult-to-treat diseases. Young people will suffer the most, the disease will cut off their lives and careers early, from which our social structures will undergo huge deformations. Our highly interconnected economic system has managed to reduce poverty to historic levels, but it will begin to collapse, creating a positive feedback loop and causing more illness and disruption.
Of course, maybe none of this will happen. But consider the worst-case scenario: new strains of tuberculosis, combined with climate-related crop failures, will lead to mass migration. The result could be an unstoppable epidemic that would end the modern economy. We are more vulnerable than we think: the white death may return.
Drew Smith is a molecular biologist at the University of Colorado at Boulder. He was a scientist and director of research projects in several biotech and medical companies, one of which developed methods for the diagnosis of infectious diseases.
Drew Smith