德尔塔变体是新冠病毒的一种版本，自它首次在印度被发现以来，已经在80个国家和地区被发现。它的名字来自于世卫组织，该组织以希腊字母命名影响巨大的变体。
Viruses always mutate, and most changes are not worrying. There is concern, however, that some variants might change enough to be more transmissible, make people sicker or avoid the protection of vaccines.
病毒总是会变异，并且大多数变异无需担心。然而，人们担心某些变体可能会发生足够大的变化，从而更容易传播、感染人类或是使疫苗失效。
Experts say the delta variant spreads more easily because of mutations that make it better at connecting to cells in our bodies. In the United Kingdom, the variant is now responsible for 90 percent of all new infections. In the U.S., it represents 20 percent of infections, doubling in the past two weeks. Health officials say it could become the country's most common type as well.
专家表示，德尔塔变体更容易传播，因为突变使其更容易附着于人体细胞。该变体目前占到了英国全部新增感染的90%。在美国占到了感染的20%，其感染率在过去两周内翻了一倍。卫生官员表示，它也可能成为美国最常见的类型。
Dr. Anthony Fauci is the top disease expert in the U.S.
安东尼·福奇博士是美国顶级疾病专家。
"The delta variant is currently the greatest threat in the U.S. to our attempt to eliminate COVID-19," he said.
他说：“德尔塔变体目前是我们消灭新冠肺炎的最大威胁。”
Dr. Jacob John studies viruses at the Christian Medical College at Vellore in India. He said there is not enough data to be sure whether the variant makes people sicker. And studies have shown that vaccines work against variants, including the delta variant.
雅各布·约翰博士在印度韦格尔基督教医学院研究病毒。他说，没有足够数据证实这种变异是否会使人病情加重。研究表明，疫苗可以对抗变体，包括德尔塔变体在内。
Researchers in England studied how effective the two-dose AstraZeneca and Pfizer-BioNTech vaccines were against coronavirus variants. The vaccines protected those who got both doses, but were less effective for those who got just one dose.
英格兰的研究人员研究了两剂式的阿斯利康和辉瑞疫苗对新冠病毒变体的有效性。疫苗可以保护接种了全部两针的人群，但是对只接种了一针的人效果较差。
The American state of Missouri is seeing a sharp rise in delta variant cases because many people are not getting vaccinated. Over 53 percent of Americans have received at least one shot, says the Centers for Disease Control and Prevention.
美国密苏里州出现了德尔塔变体病例的急剧上升，因为许多人没有接种疫苗。美国疾控预防中心表示，超过53%的美国人至少接种过一针疫苗。
But many parts of Missouri are well below 40 percent. One county is at just 13 percent. Fauci said there is a "real danger" of big increases in cases in areas around the U.S with low vaccination rates.
但是密苏里州很多地区的接种率远低于40%。有个县只有13%的接种率。福奇表示，在美国各地疫苗接种率不高的地区，仍存在病例大幅增加的实际危险。
That is why experts say it is important to be fully vaccinated. And it is why they say making vaccines available worldwide is so important.
这就是为什么专家说全面接种疫苗很重要。也是他们为什么说在全球范围内提供疫苗如此重要的原因。
But it is not clear yet how long vaccines provide protection against disease.
但是目前尚不清楚疫苗对这种疾病可以提供多长时间的保护。
Mehul Suthar is with the Emory University Vaccine Center. He said the current vaccines are designed to work against one spike protein on the coronavirus. The spike protein is the part of the virus that attaches to human cells and is targeted by vaccines.
Mehul Suthar在埃默里大学疫苗中心工作。他说，现有疫苗旨在对抗新冠病毒的一种刺突蛋白。刺突蛋白是病毒附着于人体细胞上的部分，它是疫苗针对的目标。
Suthar said if the virus mutates enough over time, vaccines might also need to change to improve their effectiveness.
Suthar表示，如果病毒随着时间推移发生足够大变异，疫苗可能也需要改变以提高其有效性。
I'm Dan Novak.
我是丹·诺瓦克。(51VOA.COM原创翻译，请勿转载，违者必究！)