COVID-19 updates 10/30/20(2) 「人の鎖モデル」: 感染伝播のしくみの理解のために “Chain of People Model” for understanding the mechanism of infection transmission

人は何らかの関係で誰かとつながっているので、例えば、鎖ひとつを1人とみなすと、人のつながりを鎖のつながりとみなすことができます。1億人の人口集団も、1番目から1億人目まで順につながる一本の長い「人の鎖」とみなすことができるものとします。

人の集団は、この1本の鎖が絡まるように生活空間内に存在しているものと考えられます。何個かの連続した鎖の部分は、隣に走る同じように連続した鎖と接していますが、これらは実はお互いに元々1本の鎖の一部分どうしです。そのようにして複数の連続した鎖どうしがたくさんの場所で接しています。

感染症が圧倒的に高い確率で濃厚感染経由で伝染していくのは、この1本の鎖を辿って伝染していくようなものです。ちょうど電気が一番流れやすいところを通って流れていくようなものです。

鎖ひとつをもう少しまとめて10人の集団とみなすこともできます。鎖どうしの接点は隣接する集団各々の1人ずつです。鎖一つの中で起こるのが「家庭内類似感染」、鎖どうしの接点で起こる、つまりたった1人を媒介してでも起こるのが「コミュニティ感染」です。

たまに隣を走る鎖と複数個所で交差したり接触したりしている場所では、一度に多くの鎖に伝染してしまいます。電気がショートするようにです。

パンデミックは鎖の一か所から始まります。しばらくは直接つながった隣の鎖にだけ順に伝染していたものが、複数の鎖が接触した場所を通じていっぺんに感染が広がり、1億個の長い鎖の中の互いに離れた多数の場所が感染源になっていきます。そしてそれらの場所からさらに直接つながった鎖に沿って感染が伝播していきます。

一旦ウイルスが一地域に持ち込まれるとなかなか消滅しない現象も、20歳代という限定した年齢層に感染が集中してなかなか途切れない現象も、鎖を作る宿主どうしのつながりゆえに起こるものとして説明できます。
多人数の集まりは、鎖の交差・接触点の増大とみなすことができます。
鎖の1か所に免疫ができていればそこで伝染は止まります。免疫力が持続しなければ、その部位では再び感染伝播が生じます。

Since people are connected to someone in some way, for example, if we consider a single chain to be a single person, we can consider the connections between people to be links in a chain connected by some kind of relationship; let's assume that a population group of 100 million people can be considered a single long "chain of people" that leads from the first to the 100 millionth person in that order.

A group of people can be thought of as existing within a living space as this single chain of people intertwined. Several consecutive parts of the chain are in contact with similar chains running next to each other. But these are actually parts of a chain that were originally part of a chain, and so there are many parts of chains that are in contact with each other in many places.

The overwhelmingly high probability of an infection being transmitted via concentrated infection means that the probability of infection being transmitted via this one chain is high. It is just like electricity flowing through the places where it is most likely to flow.

One chain can be grouped a little more together and considered a group of ten people. The contact point for the next chain is one person. What happens in a chain is "household-like infection", and what happens at the point of contact between the chains, even if it is transmitted by just one person, is "community infection".

Occasionally, where there is any number of intersections or contacts with the chain connections that run next to each other, it can be contagious to many chains at once. It's like a short circuit.

A pandemic begins at a single location on a chain. For a while, it only infects neighboring chains directly connected to each other, but it becomes contagious at once through the point of contact of multiple chains, with many locations separated from each other in a long chain of 100 million pieces being the source of infection. And from there, it can be transmitted again along the directly connected chains.

The phenomenon that the virus does not readily disappear once it is introduced into a region, and the phenomenon that the infection is concentrated in a limited age group of 20-year-olds and is not easily interrupted, can be explained as occurring because of the linkage between hosts that form the chain.
A large gathering of a large number of people can be regarded as an increase in the number of intersections and contact points of the chain.
If immunity is built up at one point in the chain, the infection stops there. If the immunity is not sustained, the transmission of the infection will occur again at that site.

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