Zhou Muzhi, professor of Tokyo Keizai University
There had been 1.5 COVID-19 deaths among every 100,000 Japanese by Nov. 11, 2020. This was a “slight” death rate compared with Spain’s 58.8, the U.S.’ 74.6, the U.K.’s 74, Italy’s 71.1, France’s 65.1, and Germany’s 14.1. The question is raised that how Japan managed to control its COVID deaths at such a low level, while implementing the “Coexisting with COVID-19 Policy” that European countries and the U.S. all deployed.
Among all speculations trying to explain Japan’s low death level, I think “cross-immunity” is the most compelling one. The theory opined that the immunity acquired by the Japanese people has played a role to some extent in preventing COVID-19 or mitigating its symptoms.
The question here is how Japanese people acquired cross-immunity against the novel coronavirus.
U.S. expert Jared M. Diamond hypothesized in his “Guns, Germs, and Steel: The Fates of Human Societies” that during the long time of close contact with poultry, European people became immune to many pathogenic bacteria. On the contrary, as Americas had no domesticated poultry, native people there lacked immunity to bacteria. The European people brought bacteria to Americas in the age of great navigation. The bacteria wreaked havoc on natives who lacked immunity, wiping out population .
I agree with Jared M. Diamond’s hypothesis that Europeans obtained immunity from their long-time close contact with poultry. However, the hypothesis failed to explain why European countries were greatly eclipsed by Japan in terms of the number of COVID-19 deaths, despite of the fact they are all in Eurasia. What’s more, besides Japan, other East Asian countries, including China, all reported smaller numbers of COVID-19 deaths
By Nov. 11, China, South Korea, China’s Taiwan province and Hong Kong Special Administrative Region, Vietnam, and Thailand registered 0.3, 0.9, 0.03, 1.4, 0.04 and 0.09 COVID-19 deaths per 100,000 people, respectively, “very minor” compared with European countries rich in medical resources. Such relatively good performances, though largely due to the “Zero COVID-19 Case Policy,” have also benefited from cross immunity.
I hereby put forward a hypothesis that the lifestyle centering on rice fields in humid regions of East Asia plays a determining role in people’s acquisition of cross immunity against the novel coronavirus. The “Zhou Muzhi Hypothesis” is detailed as follows: The humid rice-growing Satoyama boasts rich ecological diversity, and a new ecology formed upon a moderate intervention of human beings in nature, one with richer diversity than primitive natural ecology. The diversity is also reflected in microorganisms. In Satoyama, human beings, nature, and poultry are in close contact and influence each other, shaping a huge breeding spot for pathogens. This place is richer in microorganism diversity than Europe, though they both belong to Eurasia. Therefore, I infer that people living in rice-growing regions with a variety of pathogens have stronger cross immunity .
Studies on cross immunity against novel coronavirus are still in their infancy. The recent research findings published by Manish Sagar of Boston University confirmed that people who have been infected with seasonal coronaviruses can develop cross immunity against novel coronavirus, thus alleviating severe symptoms . Tatsuhiko Kodama from the Isotope Science Center at the University of Tokyo found through an analysis of the blood of 50 COVID-19 patients in Japan that 75% of the patients have cross immunity against the novel coronavirus .
In fact, seasonal coronaviruses have been frequently around in the humid regions of East Asia. If they can help people develop cross immunity against the novel coronavirus, it should be a grace of living in the rice-growing Satoyama.
From this perspective, it is important and worthwhile to think how to evaluate the life in Satoyama where people and nature influence each other, and how to draw on experience from Satoyama lifestyle in our modern life.
(The English version of this article is translated by Chen Linfeng.)
The article was published on China Net on May 12, 2021, and was republished by foreign media, as well as today’s headlines and other platforms.