2007年VOA标准英语-Study Finds Drug Resistance Fades Quickly in Ke

By David McAlary
Washington
10 January 2007

One of the main weapons to prevent mother-to-child transmission of the AIDS virus during birth is the drug nevirapine. But when nevirapine is used alone just once, HIV starts becoming resistant¹ to it.  Research in Botswana shows that the resistance is not long lasting² and that this affordable³ drug does not have to be abandoned forever by infected mothers who have already taken it. VOA's David McAlary reports.

A baby sleeps in her mother's arms next to the anti-AIDS drug nevirapine

International medical guidelines call for pregnant women with advanced HIV to get a combination of AIDS drugs including nevirapine to prevent passing their infection on to their newborns during delivery. But in poor countries, combinations have been expensive and nevirapine has often been used alone, since studies have shown that a single dose can cut the transmission rate in half.

The problem is that HIV resistance builds against it quickly when used alone just once because other drugs are not present to kill the virus particles that survive nevirapine. This renders the drug less effective in later combinations for treating women after their baby is born.

But the new study from Botswana shows that nevirapine can make a comeback for these women if they wait until the resistance subsides⁴.

"The longer out you get from that exposure to single dose nevirapine, the less detectable⁵ nevirapine resistance is," said Shahin Lockman of the Harvard School of Public Health in Boston.

She is lead author of the study and she notes that the waiting period for women who get the single dose of nevirapine at delivery can be as short as six months.

"If they started nevirapine-based treatment six or more months after nevirapine exposure, their treatment response was just as good, and really quite high, compared to women who did not have the single dose of nevirapine," she added.  "However, the women who started nevirapine-based treatment within six months of that nevirapine exposure were much more likely to experience treatment failure."

The study published in the New England Journal of Medicine shows that waiting at least six months means that HIV-positive women are 70 percent more likely to benefit from nevirapine-based drug combinations again than women who get them sooner.

An official with the U.S. government health agency that helped fund the study calls it very important.

Lynne Mofenson is chief of research on child, adolescent, and maternal⁶ AIDS at the U.S. National Institute of Child Health and Human Development. She says the finding supports a World Health Organization (WHO) recommendation restricting a single dose of nevirapine only to pregnant HIV-infected women who are healthy enough to wait six months after childbirth for more nevirapine-based therapy. Otherwise, they should get other drugs during labor⁷.

"It shows the importance of screening women for treatment while they are pregnant and putting them on appropriate therapy while they are pregnant to avoid having to start them too soon after they received preventive therapy," she explained. 

Shahin Lockman in Boston says the problem of nevirapine resistance should diminish now that more and more people are receiving combinations of AIDS drugs under expanded U.S. and international programs to deliver them to Africa and other regions hard hit by the virus.

1 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

2 lasting   

adj.永久的，永恒的；vbl.持续，维持

参考例句：

• The lasting war debased the value of the dollar.持久的战争使美元贬值。
• We hope for a lasting settlement of all these troubles.我们希望这些纠纷能获得永久的解决。

3 affordable   

adj.支付得起的，不太昂贵的

参考例句：

• The rent for the four-roomed house is affordable.四居室房屋的房租付得起。
• There are few affordable apartments in big cities.在大城市中没有几所公寓是便宜的。

4 subsides   

v.（土地）下陷（因在地下采矿）( subside的第三人称单数 )；减弱；下降至较低或正常水平；一下子坐在椅子等上

参考例句：

• Emotion swells and subsides. 情绪忽高忽低。 来自《现代汉英综合大词典》
• His emotion swells and subsides. 他的情绪忽高忽低。 来自《现代英汉综合大词典》

5 detectable   

adj.可发觉的；可查明的

参考例句：

• The noise is barely detectable by the human ear.人的耳朵几乎是察觉不到这种噪音的。
• The inflection point at this PH is barely detectable.在此PH值下，拐点不易发现。

6 maternal   

adj.母亲的，母亲般的，母系的，母方的

参考例句：

• He is my maternal uncle.他是我舅舅。
• The sight of the hopeless little boy aroused her maternal instincts.那个绝望的小男孩的模样唤起了她的母性。

7 labor   

n.劳动，努力，工作，劳工；分娩；vi.劳动，努力，苦干；vt.详细分析；麻烦

参考例句：

• We are never late in satisfying him for his labor.我们从不延误付给他劳动报酬。
• He was completely spent after two weeks of hard labor.艰苦劳动两周后，他已经疲惫不堪了。