The Conversation Spain
Control of infectious diseases is humanity’s greatest revolution
Víctor Coyote / Telos A decisive milestone in the advancement of human civilization has been to recognize that diseases do not respond to a supernatural origin or are the result of “bad airs”, but rather have a tangible and real origin and that only by knowing this origin will we be able to prevent and cure them. A paradigm of this milestone has been infectious diseases, because in this case the first step to combat them has always been to know their origin, the pathogen that produces them. The year 2020 will go down in history due to the covid-19 pandemic, showing that infectious diseases are not a thing of the past and that they can even help us to be more effective in biomedical research. Guidelines for identifying pathogens Robert Koch, a German physician and father of microbiology, established the scientific methodology to identify the agents that cause infectious diseases –also called communicable– and thus be able to combat them. These are Koch’s postulates, which indicate that in order to find the pathogen that causes a disease, the following facts must be met: The pathogenic organism must be in sick people and not in healthy people It must be possible to extract it from a sick person and grow it in a lab. The isolated pathogen must be able to reproduce the disease when introduced into healthy people. People infected with this pathogen should develop the same symptoms as sick people from whom the pathogen was originally isolated. In the case of the Spanish flu of 1919-1920, the infectious agent causing the disease was never known despite the efforts of a few scientists in the US, France and Germany. They applied Koch’s postulates to strains of bacteria isolated from sick patients that they thought might be the cause of the disease. However, the isolated bacteria did not comply with Koch’s postulates and, therefore, had to be ruled out as the origin of the Spanish flu. Not knowing the germ that produced the Spanish flu, no effective treatments or vaccines could be developed and the pandemic caused some 40 million deaths worldwide. We now know that the causative germ was not a bacterium, but a virus, the influenza A virus, subtype H1N1. telos health notebook maria blasco illustrates victor coyote. Víctor coyote / TELOS The case of HIV When a little more than half a century later AIDS broke out as a strange cancer that affected homosexuals, scientists Robert Gallo and Luc Montagnier were the protagonists of a career full of intrigue to be the first to isolate the pathogen causing the disease. They knew that the only way to control the AIDS pandemic was to find the pathogen that caused it. Luc Montagnier and his team succeeded two years later, isolating the human immunodeficiency virus, or HIV. Until then, the life expectancy of an AIDS patient was just over two years and patients developed severe respiratory problems and skin tumors called Kaposi’s sarcoma. No treatment aimed at curing these pathologies was able to stop the fatal course of the disease. Only when the HIV virus was identified was it possible to find out how the disease was transmitted, how infected people could be detected to prevent them from transmitting it to other people and, above all, it allowed for effective treatments that today save the lives of dozens of thousands of people. The identification of SARS-COV-2 If in the case of AIDS it took two years to find out the infectious agent that caused the disease, in the case of the new Wuhan pneumonia (covid-19) it was a matter of weeks. Chinese scientists, including the virologist from the Wuhan Center for Virology Shi Zengli, described that it was a new coronavirus, SARS-COV-2, very similar to the one that caused the SARS disease and also discovered by Zengli. Knowing the pathogen that caused COVID-19 made treatments that could block its entry into cells or its ability to multiply begin to be tested almost immediately. Just a few months later, several vaccines were being tested and not before the end of the year some countries had already started vaccinating vulnerable groups. Likewise, dozens of new treatments are being developed to block the entry of the virus into cells, to block its ability to multiply and to treat the effects of the virus in the body. Undoubtedly, it will be advances in research that will help us overcome the global crisis caused by this new virus. We are not mistaken if we affirm that the control of infectious diseases has been the greatest revolution of humanity or at least the one that has had the greatest impact on our lives and, therefore, on the advancement of the 20th century. Life expectancy at birth in Europe was just over thirty years. This was due to a very high infant mortality and the risk of dying was high at any time in life; a simple bacterial infection could make us seriously ill and die. To what extent can we apply what we have learned from the control and treatment of infectious diseases to the treatment of other types of diseases, many of which are incurable today? Non-infectious diseases In the 21st century, the increased risk of death in developed countries is concentrated in the last decades of life and is mainly caused by diseases associated with the body’s aging process. These diseases include most adult cancers, degenerative diseases of different organs (lung, kidney, liver, etc.) and neurodegenerative, as well as cardiovascular diseases, among others. The incidence of these diseases is increasing in a very significant way due to the demographic aging of the population, which will mean that, for example, in Spain in 2050 more than a third of the population will be over 65 years of age. Although many of these diseases have been studied for decades, they have yet to be prevented or cured with effective treatments, and this is in contrast to the successes with infectious diseases. Many researchers think that the reason why these diseases have not been controlled is that their origin has been ignored, which in this case is not a virus or a bacteria, but the molecular aging process of the body. The situation would be analogous to when the tumors of patients with AIDS were treated, but the disease continued to progress and patients died, since the origin, which was HIV, had not been eliminated. Therefore, until treatments based on prevention and slowing down or elimination of the cellular aging process are designed, we will not be able to prevent and cure most of humanity’s diseases. Over the last twenty years, some of the molecular origins of aging have been found out, and it has been shown in animal models that aging can be delayed and thereby delay the onset of associated diseases, including cancer. In a similar way to Koch’s postulates to control infectious diseases, demonstrating the molecular origin of a non-infectious disease would be the only way to prevent or cure it. To some extent this has already happened in the case of cancer: cancer patients are currently being treated based on the origin of their tumor, based on the gene or genes altered in that particular tumor. Thanks to this, mortality is being reduced in many previously incurable cancers. Preventive treatments to block the harmful effects of mutations could be a way to prevent tumors associated with these alterations. Half a century later The next step would be to cure degenerative diseases of aging using therapies aimed at reversing or stopping molecular aging. If these strategies are successful, it is very likely that we will enter humanity’s next great revolution, analogous to the one that occurred in the 20th century with the control of infectious diseases and that doubled or tripled life expectancy at birth. On this occasion, the increase in life expectancy in good health could be even more significant. Richard Feynman – Nobel Prize in Physics in 1965 – said that we are at the beginning of the evolution of the human species. That can certainly change if we are able to control all diseases. The original version of this article was published in the Telos Magazine of Fundación Telefónica. This article was originally published on The Conversation. Read the original. María Blasco Marhuenda is a collaborator of TELOS, of Fundación Telefónica. The original version of this article comes from this publication.