Research press release


Nature Microbiology

1.65 million childbearing women at risk of Zika infection in the Americas



Alex Perkinsたちは、米州人口のうち、ジカウイルス感染のリスクがある人の割合を見積もるこれまでより優れた方法を考案した。この方法はこれまでの推定方法に、集団免疫(社会の中でジカ感染に対する免疫を持つ人が必要な最小人数を超えると、社会の残りの人たちが間接的に免疫される)や基本再生産数(完全に免疫を持たない集団に入った1人の感染者が生じさせる新しい感染者の推定数)といった生態学理論を加味した改良法である。これらの理論を、実際の集団内のジカ感染レベル(血清を測定した血清陽性率)やウイルス伝播の推進要因について空間的に詳しく解析したデータと組み合わせて、場所に応じたジカウイルスの感染率を予測した。ジカ特異的なウイルス伝播のパラメーターはまだほとんど分かっていないので、より現実的な予測をするために、著者たちはデングウイルスやチクングニアウイルスの流行から得た情報を利用している。この予測を、信憑性のある最悪のシナリオとして、あるいは最初の局所的流行があると仮定した場合のその大きさの予測と受け止めるべきだと、著者たちは述べている。

More than 1.6 (1.45-2.06) million childbearing women and 93.4 (81.6-117.1) million people in total in the Americas could become infected during the current wave of the Zika virus epidemic, according to a model-based projection published online in Nature Microbiology this week. The study suggests that, based on current rates of adverse fetal outcomes in infected women, tens of thousands of pregnancies could be affected.

Zika virus is a mosquito-borne pathogen that has been associated with a range of fetal developmental conditions, including congenital microcephaly, during its rapid spread across the Americas. As of 30 June there have been 1,674 confirmed cases of microcephaly associated with Zika virus infection in five countries. At present there is no vaccine available for preventing Zika virus infection.

Alex Perkins and colleagues formulated an improved method for estimating the portion of the population in the Americas that is at risk of Zika virus infection. The method is an improvement of previous estimates because it takes into account ecological theories such as herd immunity - when immunity to Zika infection in the community surpasses a critical mass and confers indirect immunity on the rest of the population - and basic reproduction number (the estimated number of new people that one infected person can infect in a completely susceptible population). They combined these theories with actual levels of Zika infection in the population - as measured by blood serum (seroprevalence data) - and highly spatially resolved data about drivers of transmission to make location-specific projections of Zika virus attack rates. As Zika-specific transmission parameters are still largely unknown, the authors used information from epidemics of dengue virus and Chikungunya virus to produce a more realistic projection. The authors note that their projections should be interpreted as either a plausible worse-case scenario or an expectation of local epidemic size, conditional on there being a local epidemic in the first place.

doi: 10.1038/nmicrobiol.2016.126


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、毎週各ジャーナルからの最新の「注目のハイライト」をまとめて皆様にお届けいたします。