Columns that reveal the world
- Getting up close and personal with the researchers -

Humanity is often exposed to the threat of infectious diseases, and right now the whole world is at the mercy of new infectious diseases (emerging infectious diseases). In fact, there is only one infectious disease that humanity has succeeded in conquering: smallpox. Smallpox, which is believed to have existed since before Christ, is highly contagious and often fatal, claiming the lives of people around the world until the second half of the 20th century. In the mid-20th century, there were more than 10 million patients every year, and approximately 2 million people died. There were frequent epidemics in Japan as well.

Smallpox was brought under control at the end of the 18th century when Edward Jenner succeeded in developing a vaccine (vaccination) to prevent the smallpox virus. Jenner noticed that people who milked cows rarely contracted smallpox. He also knew from experience that people who had contracted smallpox once would not contract it again. He then established a revolutionary method called "vaccination," which involves acquiring immunity by inoculating people with cowpox (a type of virus that is not highly toxic). This method was later introduced to Japan. Before "cowpox," a method called "variola," in which people would intentionally contract smallpox in an attempt to acquire immunity, was practiced all over the world. However, this method is said to have actually contributed to the spread of smallpox.

The World Health Organization (WHO) formulated a plan to eradicate smallpox worldwide in 1958, and developed a vaccine and vaccination program. However, vaccination of everyone ultimately did not work. Instead, they found smallpox patients and vaccinated people in their vicinity. This method is similar to the cluster control measures being used around the world for the new coronavirus infection.

The success of the smallpox countermeasures led by the WHO was the result of "international cooperation." The fact that there was cooperation in smallpox countermeasures even during the Cold War between the United States and the Soviet Union was significant, and shows that "international cooperation" is essential to control infectious diseases that spread across borders. This is especially important now, when international friction is intensifying amid the spread of the new coronavirus. This is how the first and only declaration of smallpox eradication in human history was made in May 1980.

The 2020 novel coronavirus has had an enormous social impact. Countries around the world, including Japan, have been forced into a state of virtual isolation, with economic activity, social life, and schools being suspended. This was the first time in the history of public health that such measures had been taken.

Many people may have noticed the differences in the medical systems of each country. The issue of "who cures illness" is at the foundation of each country's medical system. If illness is considered an individual's problem, the government does not need to be involved. In response to this, some countries have taken generous measures. Attitudes toward illness and medical care vary greatly from country to country. For example, the United States and the United Kingdom are both countries with advanced medical technology, but the United States does not have a universal health insurance system like Japan, and there is a strong view that curing illness is the individual's responsibility. In contrast, the United Kingdom has a medical system called the NHS (National Health Service) run by the government, and in principle, medical care is free of charge. However, this does not mean that you can visit a medical institution casually; you must visit a family doctor called a gatekeeper, and even if you get sick, you may have to wait about a week.

A "small government" that limits national spending and leaves it up to individual responsibility, and a "big government" that provides generous welfare services but imposes a heavy tax burden - each have their advantages and disadvantages, and it is not possible to say which is better. So, which system does Japan have? Also, are medical care and public health functioning adequately? This is a question of political culture, and also of what form has been sought historically. When considering the state of medical care and society, various perspectives are needed in addition to medicine and public health. An understanding from history can be useful, along with economics and psychology.

History is good at "recording and passing on to future generations." When the spread of the new coronavirus infection first began to become a problem, I reread newspapers from 2009, when a new strain of influenza was spreading worldwide. The newspapers mentioned the same issues as today, such as a shortage of masks and the importance of social distancing. Experts at the time also thought about the future and recommended preparations, but unfortunately people quickly forget. In Japan's case, public attention shifted to the Great East Japan Earthquake that occurred in 2011, and awareness of infectious disease prevention measures also waned.

Infectious diseases in human history can be traced back approximately 10,000 years. A major turning point is thought to have been the start of agriculture approximately 10,000 years ago. When forests were cleared to expand farmland, the possibility of crossing over with pathogens that were present in the forest also increased. Many pathogens likely came into contact with human life as wild animals were domesticated. Compared to hunter-gatherer lifestyles, agricultural societies had lower risks in childbirth and child-rearing, so women tended to have shorter birth intervals and more children (population). As a result, the population increased and urbanization progressed. These various human activities provided opportunities for the spread of many infectious diseases.

When Columbus and others "arrived" in the New World in the 15th century, the exchange of people and goods became more active (Colombian exchange), and the exchange of pathogens also became more active, leading to the spread of infectious diseases around the world. Smallpox is a symbol of this. When European smallpox was brought to the Americas, many native people lost their lives and colonization progressed. Smallpox changed history.

Japan has succeeded in eliminating malaria, which was endemic throughout the Japanese archipelago and the Okinawa Islands. Therefore, there is currently concern about imported malaria (when people infected overseas return to Japan and develop symptoms). However, as global warming expands the areas in which malaria-carrying mosquitoes can live, there is concern that malaria infections will reemerge in Japan (re-emerging infectious diseases). One such infectious disease is dengue fever. It is still fresh in our memory that a few years ago, dengue fever, which was thought to be a disease unique to the tropics, broke out in Tokyo and caused problems.

Malaria is an infectious disease that still kills hundreds of thousands of people every year around the world. After World War II, malaria was eradicated using DDT in Japan and other parts of the world, and progress was made in eradicating malaria. However, when the toxicity of DDT was revealed in the book Silent Spring written by Rachel Carson, DDT could no longer be used. Currently, one of the most effective methods for combating malaria is the distribution of mosquito nets to prevent mosquito vectors, and this method is being tried out as part of medical aid in Africa and other places.

In this context, Japan's experience in controlling malaria may be useful in controlling infectious diseases in developing countries. In addition to malaria, Japan's experience in eliminating parasitic diseases such as lymphatic filariasis and Japanese schistosomiasis may provide wisdom that can be used to improve life in developing countries where these infectious diseases remain major health problems. To do this, it is necessary to organize, preserve, and utilize historical materials that show the process of infectious disease control. This is called "historical epidemiology."

Many people seem to have the image that history deals with the "past" and that the "past" is something fixed. This is incorrect. The "past" is constantly changing in dialogue with the present. In other words, when our understanding of the present changes, the "past" also changes.

Past events can only be clarified through the process of historicization. History is the academic field that is responsible for this historicization, and it is a very important task for history to record what is happening now and pass it on to future generations. Recording the people living today is also very important. For example, the behavioral changes currently required as a measure against the new coronavirus are having a huge impact on our lives. What are we anxious about, what are we worried about, and what do we find enjoyable? These are not easily recorded, and are more likely to be lost. So, first of all, I began an attempt to record the feelings of the students I interact with on a daily basis. Recording the feelings of these people is also the job of history. This may not be immediately useful. However, it goes without saying that the next time there is an epidemic, it will be a very important resource for countermeasures.

Before the "history of infectious diseases" gained attention, the "history of disasters" had been attracting attention. This was related to the Great East Japan Earthquake of 2011 and the various disasters that have been increasing in recent years. In the past, disasters and infectious diseases were rarely written about in history textbooks. However, in the future, the earthquake and the current COVID-19 pandemic will likely be considered as history. I hope that you will take part in these instances where the "past" is "historicized."

(Published in June 2020)