Drug Resistance¹ Fades Quickly in Key AIDS² Drug

    One of the main weapons to prevent mother-to-child transmission of the AIDS virus during birth is the drug nevirapine³. But when nevirapine is used alone just once，HTV⁴ starts becoming resistant to it. Research in Botswanashows that the resistance is not long lasting and that this affordable drug does not have to be abandoned forever by infected mothers who have already taken it.

    International medical guidelines call for⁵ pregnant women with advanced HTV 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 fromBotswanashows that nevirapine can make a comeback for these women if they wait until the resistance subsides.

    "The further out you get from that exposure to single dose nevirapine, the less detectable nevirapine resistance is⁶，” said Shahin Lockman of the Harvard School of Public Health in Boston⁷. She says 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 response⁸ 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 Medicine⁹ 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 theU. S.government health agency that helped fund the study calls it very important.

    Lynne Mofenson is chief of research on child, adolescent, and maternal AIDS at the U. S. National Institute of Child Health and Human Development¹⁰. She says the finding supports a World Health Organization (WHO)¹¹ 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 labor. “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 inBostonsays the problem of nevirapine resistance should diminish now that¹² more and more people are receiving combinations of AIDS drugs under expandedU. S.and international programs to deliver them toAfricaand other regions hard hit by the virus.

词汇：

fade /feɪd/ vi. 消失 

affordable / ə"fɔ:dəbl / adj. 负担得起的，能提供的
transmission /trænsˈmɪʃn / n. 传播；传染；遗传 

abandon / ə"bændən / vt.  抛弃，放弃
Botswana 博茨瓦纳（非洲）

advanced n. 晚期的
newborn  /ˈnju:bɔ:n/ adj. 新生的；新生儿 

delivery /dɪˈlɪvəri / n. 分娩，生产

dose /dəʊs/ n. （一次）剂量，一剂
render / ˈrendə(r) / v. 使得，致使

comeback /ˈkʌmbæk/ n. 东山再起；还原；补偿
detectable /diˈtektəbl/ adj.可查明的；可找出的 

positive  /ˈpɒzətɪv/ adj. 阳性的
adolescent /ˌædəˈlesnt/ adj. 青年期的，青春的；青少年（12或13岁-20岁）

maternal /məˈtɜ:nl/ adj. 母亲的 

restrict / rɪˈstrɪkt / vt. 限制

pregnant  /ˈpregnənt/ adj. 怀孕的
childbirth /ˈtʃaɪldbɜ:θ/ n. 生孩子，分娩 

therapy /ˈθerəpi/ n. 疗法，治疗
preventive  /prɪˈventɪv/ adj. 预防的 

diminish /dɪˈmɪnɪʃ / vt.  减少，缩小

注释：

1.drug resistance:抗药性
2.AIDS (acquired immunodeficiency syndrome)：获得性免疫缺损综合征，艾滋病
3.nevirapine (NVP):奈韦拉平。一种阻断HIV母婴传播的新药。其品牌名为Viramune。
4. HIV (human immunodeficiency virus)：人体免疫缺损病毒
5.call for:要求；提倡；号召
6.The further out you get from that exposure to single dose nevirapine, the less detectable nevirapine resistance is. ? ?:你月艮用一剂nevirapine之后，时间越长越不易发现(HIV)对 nevirapine的抗药性……get out from:从……离开，从……出发（在本句中如直译就是： 从……走出去,走得越远就越……）。exposure to:暴露；接触（在本句中如直译就是：接触 一剂 nevirapine) 0
7.Harvard School of Public Health in Boston:波士顿哈佛公共卫生学院
8.response的原意是“反应，应答”，但在医学文献中常用来指“疗效”，此处treatment response 就更加明显。
9.New England Journal of Medicine ：《新英格兰医药杂志》。New England是美国东北部 Maine, Vermont, New Hampshire, Massachusetts, Rhode Island 和 Connecticut 六州的总称。
10. U. S. National Institute of Child Health and Human Development (NICHHD):美国国立儿童 健康与人类发展研究所
11.World Health Organization (WHO)：世界卫生组织
12.now that:既然，因为

When may a woman start her nevirapine-based treatment if she gets the single dose of nevirapine at delivery?

A:She may start nevirapine-based treatment soon after her delivery B:She may start nevirapine-based treatment within six months after her delivery C:She has to wait at least six months after that nevirapine exposure D:She may wait several years so as to achieve the best effect

(Everybody) (has arrived.) (It’s) time we (shall start).（　）

A:Everybody B:has arrived C:It’s D:shall start

You should (check) the air in the (tires) (as) you (start on) a long automobile trip.

A:check B:tires C:as D:start

"I suspect that your business will start that way too." in the last paragraph means ______. ( )

A:I doubt you will start a business in the same way B:I don't believe your business will succeed if you start that way C:I think it is likely you start a business that way D:I have no idea if you will start a business that way

" When is the concert supposed to start"
"It ______ now.

A:is about starting B:was about to start C:is about to start D:was about starting

START

(A) MOV AH, 0 ; 设初值
(B) ADD BX，AX ; 第一次求和
(C) AL
(D) INC DI ; 移动地址让上个数的所得结果和下个数相加
(E) BX ; 保存数据[解析] 此题是一个求和的问题，NEXT中用循环指令求和。先设一个初值为0，让它和内存中存储的第一个数据相加，然后让所得结果和下一个数相加，直到循环结束为止。

START

(A) CMP AL, 0 ; 比较，看AL中的内容是否为负数
(B) NEXT
(C) NEG AL ; 对负数求补
(D) ADC DH，0 ; 判断是否有进位
(E) 0
(F) REP STOSB[解析] 本程序的功能是从所给的数据中取出负数并计算绝对值之和。CON所完成的是判断数据，如果是负数则取反加1，即变为它的绝对值再求和。否则转到NEXT中，继续循环判断数据，直到所有数据判断完。NEXT中完成的是多余的空间存入0。汇编语言中存入串指令用STOS，当有重复存入时加前缀REP，执行的足把AL或AX的内容存入一个长度为(CX)的缓冲区中。

START

(A) MOV AH, 0 ; 设初值
(B) SI ; 向下移动地址，对下一个数据进行计算
(C) J ; 判断数据是否超出该行的范围
(D) B ; 保存所求的数据，下移两个单位是因为数据为字的形式
(E) LOOPA[解析] 程序的功能是求出每行所有数据的和，该功能在LOP2中完成。首先从矩阵第一行第一列的数据开始算起，和该行的下一列数据求和，直到判断下个数据的计算个数超过 2时，说明该行结束。然后保存该行计算完的和，注意，保存的数据应该是字的形式。