Pre-symptomatic transmission

無症状（PCR検査は陽性だが、症状が全くない）のケースからの感染はこれまで確認されていない。つまり、感染させるリスクのある人は軽度であったとしても何らかの症状があるはず。

うーん、それは微妙かなあ。

Data from published epidemiology and virologic studies provide evidence that COVID-19 is primarily transmitted from symptomatic people to others who are in close contact through respiratory droplets, by direct contact with infected persons, or by contact with contaminated objects and surfaces

感染経路は　感染者の呼気にとまなう飛沫、ないし、ウイルスのついた表面への接触

Pre-symptomatic transmission

The incubation period for COVID-19, which is the time between exposure to the virus (becoming infected) and symptom onset, is on average 5-6 days, however can be up to 14 days. During this period, also known as the “presymptomatic” period, some infected persons can be contagious. Therefore, transmission from a pre-symptomatic case can occur before symptom onset.
In a small number of case reports and studies, pre-symptomatic transmission has been documented through contact
tracing efforts and enhanced investigation of clusters of confirmed cases. 12-17 This is supported by data suggesting that some people can test positive for COVID-19 from 1-3 days before they develop symptoms.

感染してから、症状が出るまでの潜伏期間は平均して、５－６日だが、１４日に渡ることもある。この潜伏期間に感染者が他人にウイルスを感染させることもある。発症以前に感染させることもあるんだ、と。

Asymptomatic transmission
An asymptomatic laboratory-confirmed case is a person infected with COVID-19 who does not develop symptoms.
Asymptomatic transmission refers to transmission of the virus from a person, who does not develop symptoms.
There are few reports of laboratory-confirmed cases who are truly asymptomatic, and to date, there has been no
documented asymptomatic transmission.This does not exclude the possibility that it may occur.

感染しても症状がでない場合もあるが、そうした無症状性の人から感染の例はいまだにないが、そういった場合がありえることを否定するものではない、と。


ーーずっと症状がでないで治っちゃう人の感染者から感染することはないのかもしれないが、発症前の潜伏期に感染させることはある、わけだね。だから症状がなくても、感染させるケースはある、ということだろう。

　そうしたケースは少ないのかもしれないけど、だから、発症２日前に接触した人を濃厚接触者として扱うわけなんだろうね。