60秒科学:蚊子是西尼尔病毒的传播者

Mosquitoes, Not Birds, Made West Nile National

In 1999 West Nile virus infected its first American, in New York. By 2004, the disease had spread across the country. Researchers speculated that, for the disease to spread so far so quickly, birds must have helped. Some species could carry the disease and pass it on to mosquitoes, which would then infect humans. But a report published March 2nd in the journal Molecular¹ Ecology [not available online as this episode was posted] says mosquitoes didn’t need a middleman. Or in this case, a middle bird.

Researchers [Jason Rasgon, Bloomberg School of Public Health, Johns Hopkins and Meera Venkatesan, Howard Hughes Medical Institute] noticed that West Nile virus didn't move north-south along migratory² bird routes. Nor did it "leap frog" across large areas in the manner of a bird traveling far from where it was infected.

The scientists focused on a different suspect and obtained mosquito DNA³ from 20 sites in the western U.S. They found three clusters of a species known to carry West Nile.

Surprisingly, they found extensive gene⁴ flow between these populations, which meant mosquitoes traveled between groups. In some cases, these mosquitoes covered a range just as large as that of the birds first fingered in the outbreak. So bird lovers take heart, your feathered friends are innocent avians.
 

1 molecular   

adj.分子的；克分子的

参考例句：

• The research will provide direct insight into molecular mechanisms.这项研究将使人能够直接地了解分子的机理。
• For the pressure to become zero, molecular bombardment must cease.当压强趋近于零时，分子的碰撞就停止了。

2 migratory   

n.候鸟，迁移

参考例句：

• Many migratory birds visit this lake annually.许多候鸟每年到这个湖上作短期逗留。
• This does not negate the idea of migratory aptitude.这并没有否定迁移能力这一概念。

3 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

4 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。