VOA标准英语2011--Dengue Severity Depends on Prior Infection, Genetic Variation

Dengue Severity Depends on Prior Infection, Genetic¹ Variation

 

American and Nicaraguan scientists have discovered the reason why a second infection with dengue can often be much more serious, even fatal, than the first.

Dengue is a viral disease spread by mosquitoes. The World Health Organization estimates there may be 50 million infections worldwide every year.

In some cases it causes only a mild fever. In others, the virus can cause a potentially fatal complication called dengue hemorrhagic fever.

Why some cases are mild and others are severe has been something of a mystery that scientists in the U.S. and Nicaragua have now unraveled.

There are four major varieties, or "serotypes" of dengue, and lots of genetic variation within each serotype. Also, in areas where dengue is endemic, people are often infected more than once. The first infection may result in only mild symptoms, and the body produces antibodies that will protect against the particular variety that infected them.

"Those antibodies don't necessarily work against another version of the virus, and those antibodies actually help the other version of the virus to infect the cells that it wants to infect," explained researcher Matthew Henn, of the Broad Institute in Cambridge, Massachusetts.

Scientists have unraveled the mystery of why some cases of dengue are mild while others are severe.

He said that severe symptoms are more likely when a dengue infection of a particular sub-variety meets a victim whose previous exposure to a different dengue virus has produced a particular set of antibodies.

"And if you have a certain combination of that, you're more prone² to get severe forms of the disease."

Henn says the findings of his study have implications for the so-far unsuccessful efforts to develop a dengue vaccine³. For example, the vaccine may have to be modified to account for subtypes of the virus that dominate in a particular area.

"There's a good chance that any kind of vaccine that we design for dengue is really going to have to be fine-tuned to the local setting that it may need to be used in."

1 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

2 prone   

adj.(to)易于…的，很可能…的；俯卧的

参考例句：

• Some people are prone to jump to hasty conclusions.有些人往往作出轻率的结论。
• He is prone to lose his temper when people disagree with him.人家一不同意他的意见,他就发脾气。

3 vaccine   

n.牛痘苗，疫苗；adj.牛痘的，疫苗的

参考例句：

• The polio vaccine has saved millions of lives.脊髓灰质炎疫苗挽救了数以百万计的生命。
• She takes a vaccine against influenza every fall.她每年秋季接种流感疫苗。