Research press release


Nature Communications

Epidemiology: US COVID-19 cases may be substantially underestimated

米国における2020年4月18日までのCOVID-19の新規症例数が640万例を超えていたとする確率分析の結果がNature Communications で掲載された。同じ期間中の確認されたCOVID-19の症例は、合計72万1245例だった。


今回、Jade Benjamin-Chung、Sean Wuらの研究グループは、確率的バイアス分析を行って、検査が十分に行われていないことと検査の精度が100%未満であることを補正した上で、2020年2月28日から4月18日までの期間中における米国各州のSARS-CoV-2感染者の総数を推計した。その結果、SARS-CoV-2感染症例が645万4951例(1000人当たり19人)となった。この推計値は、同じ期間中の確認症例(1000人当たり2人)の約9倍になっており、感染症例の89%が記録されていないことを意味する。この格差の大部分(約86%)は、検査が十分に行われていないことが原因であり、残りの部分は、検査の精度不足が原因だった。



The United States may have experienced over 6.4 million cases of COVID-19 by 18 April 2020, according to a probability analysis published in Nature Communications. In the same period, there were 721,245 confirmed cases.

The first known case of COVID-19 in the US was confirmed on 21 January 2020. For the first few months of the pandemic, the US Centre for Disease Control recommended that testing be prioritized for patients in hospital who tended to present moderate or severe symptoms. However, studies suggest that 30–70% of individuals who test positive for the virus present with mild symptoms or may have none at all.

Jade Benjamin-Chung, Sean Wu and colleagues estimated the total number of SARS-CoV-2 infections in each US state from 28 February to 18 April 2020 using a probabilistic bias analysis to account for incomplete testing and less than 100% test accuracy. The authors estimate that there were 6,454,951 cases of SARS-CoV-2 infection (19 per 1,000 people). This estimate is about 9 times larger than the number of confirmed cases during the same period (2 per 1,000 people) and suggests that 89% of infections were undocumented. The majority of this difference (approximately 86%) was due to incomplete testing, with the remainder due to limited test accuracy.

The authors found that COVID-19 incidence was highest in the Northeast, Midwest and Louisiana when using confirmed case counts or the estimated number of infections. Underestimation of the number of cases was more common in Puerto Rico, California and some southern states. In 33 states, the estimated number of infections was at least 10 times higher than the number of confirmed cases.

The authors note that their methodology does not incorporate a transmission model and so they are unable to make forecasts about the spread of the virus. However, they argue that their method provides a more realistic picture of infection burden at a given point in time.

doi: 10.1038/s41467-020-18272-4

「Nature 関連誌注目のハイライト」は、ネイチャー広報部門が報道関係者向けに作成したリリースを翻訳したものです。より正確かつ詳細な情報が必要な場合には、必ず原著論文をご覧ください。

メールマガジンリストの「Nature 関連誌今週のハイライト」にチェックをいれていただきますと、毎週最新のNature 関連誌のハイライトを皆様にお届けいたします。