Delta strain’s infectivity is comparable to chickenpox - CDC internal data warning

Recently CNN.co.jp reported the following:

デルタ株、水痘に匹敵する感染力　ＣＤＣの内部資料が警告

2021.07.30 Fri posted at 13:15 JST

 ワシントン（ＣＮＮ） 全米で感染が急拡大している新型コロナウイルスの変異株「デルタ株」はより重篤な症状を引き起こし、水痘と同じくらい容易に蔓延（まんえん）するとみられる。米疾病対策センター（ＣＤＣ）の内部資料から明らかになった。

資料は発表用スライドの形式で、未公開のデータを含む内容。それによるとデルタ株の場合はワクチン接種済みの人であっても未接種者と同程度の割合で感染を広げる可能性があるという。

ＣＤＣのワレンスキー所長は、資料が本物であることを確認した。資料の内容は米紙ワシントン・ポストが最初に報じた。

ワレンスキー所長はＣＮＮの取材に対し、デルタ株について「これまで知られた中で最も感染力の強いウイルスの一つ」と指摘。はしかや水痘と同水準だとの認識を示した。

ＣＤＣはデータを３０日に公表する予定。ワレンスキー氏は２７日、感染対策のマスク着用に関する指針を見直し、感染拡大地域ではワクチン接種が完了した人にも屋内での着用を勧めるとした。この決定は物議をかもしたが、新たなデータはこの内容に裏付けを与えるものとなりそうだ。

ＣＤＣの資料によると、デルタ株は１人の感染者が平均８～９人に感染させる。これは水痘と同程度。一方、変異前のコロナウイルスは通常のかぜと同じく１人の感染者から約２人にうつるという。

またデルタ株に感染した場合は、ワクチン接種者であっても未接種者と同じくらい人にうつす可能性がある。

ワクチンは９０％以上の確率で重症化を防ぐが、感染そのものの防止効果はそこまで高くない。このためワクチンを接種していても感染する「ブレークスルー感染」が起こりやすいと、資料は指摘する。

また資料では複数の報告を引用しながら、デルタ株がより重い症状を引き起こす可能性にも言及。「戦況が変わったことを認識するべき」として、ワクチン接種の義務化と誰に対してもマスク着用を求めることを推奨している。

Translation

Washington (CNN) - A variant of the new coronavirus, the Delta strain, which was spreading rapidly across the United States, was expected to cause more serious symptoms and spread as easily as chickenpox. It was made clear in an internal material of the US Centers for Disease Control and Prevention (CDC).

The material was in the form of presentation slides and contained unpublished data. According to the report, in the case of Delta strains, even vaccinated people might spread the infection at the same rate as unvaccinated people.

The CDC Director Walensky confirmed that the material was genuine. The content of the material was first reported by the Washington Post.

Walensky told CNN that the Delta strain was "one of the most infectious viruses ever known." She acknowledged that it was on par with measles and chickenpox.

The CDC would release the data on the 30th. On the 27th, Ms. Warensky reconsidered the guidelines for wearing masks to prevent infection, and said that in areas where infection was spreading, people who had completed vaccination should also wear masks indoors. While this decision was controversial, the new data was likely to support the matter.

According to CDC sources, the Delta strain would infect an average of 8-9 people per infected person. This was about the same as chickenpox. On the other hand, the pre-mutation coronavirus was said to be transmitted from one infected person to about two people like a normal cold.

Also, if a person was infected with the Delta strain, even vaccinated people could pass it on to as many people as unvaccinated people.

Vaccines had a 90% or higher probability of preventing aggravation, but the effect of preventing infection itself is not so high. For this reason, the source points out that "breakthrough infection", i.e., transmission even with vaccination, could likely to occur.

The material also mentioned that the Delta strain might cause more severe symptoms, citing multiple reports. As "we should be aware that the battle situation has changed", it recommended that vaccination be mandatory and that everyone be required to wear a mask.

              So, the Delta strain can infect an average of 8-9 people per infected person. On the other hand, the pre-mutation coronavirus is said to have the ability to cause one infected person to infect two people just like a normal cold. In view of that, I would say that Delta strain’s infectivity is about four times higher than the original coronavirus.