VOA常速英语2008年-Researchers Blame Seasonal Migration for Measle

By Jessica Berman
Washington
06 February 2008

Researchers say measles¹, which has been successfully controlled in most countries thanks to vaccination², remains³ a killer⁴ disease in Niger, in part because of migration⁵ triggered by the rainy season.  VOA's Jessica Berman reports from Washington health workers are calling for better surveillance and cooperation between public health workers and the government to control measles outbreaks.

An international team of researchers says measles epidemics⁶ in Niamey, the capital of Niger, decline at the onset⁷ of the rainy season, which is followed by sporadic⁸ epidemics of unpredictable length and frequency.  The team studied the 20-year history of the ebb⁹ and flow of measles epidemics in Niger, in an effort to determine why vaccination campaigns have failed to bring the disease under control. 

Measles is a highly infectious, airborne disease that is transmitted by coughing and sneezing among people living in densely¹⁰ populated areas. 

According to U.S. investigator¹¹ Matthew Ferrari of Pennsylvania State University, during the dry season large populations of farmers in Niger and other countries that border the Sahara desert move into urban areas for food and water. 

"The cities swell¹² in density," he said.  "Then when the rains begin, everybody moves back out to the hinterlands to pursue agriculture, resulting in lower densities¹³ of people, fewer contacts among individuals, and then reduced probability for measles transmissions to occur."

The investigators¹⁴ described their findings in the journal Nature.

Measles vaccination campaigns were successful in North America and England, according to Ferrari, because the number of births and weather conditions remained stable, which made epidemics predictable.  But he says it is hard to immunize with precision in parts of Africa because of migration. 

Measles immunization is a two-dose vaccination, with an initial shot given to children between the ages of six to 12 months, and a second, booster shot, given one month later for full protection.

Ferrari says the first shot gives children 80 percent protection against measles, but most children in Niger do not receive the booster, because they move at the end of the rainy season.

When the disease strikes, investigators found that children in Niger tend to get the disease around the age of two.

"Then what it really means is that we need to step up monitoring annually¹⁵ to identify when these large outbreaks are going to happen and get in and do these large booster campaigns in response to these outbreaks to stave them off before they sort of burn out of control," he added.

Ferrari says he and colleagues at the World Health Organization (WHO) and Doctors Without Borders (MSF) are working with the government of Niger to improve measles surveillance and delivery of vaccine¹⁶ to children.

1 measles   

n.麻疹，风疹，包虫病，痧子

参考例句：

• The doctor is quite definite about Tom having measles.医生十分肯定汤姆得了麻疹。
• The doctor told her to watch out for symptoms of measles.医生叫她注意麻疹出现的症状。

2 vaccination   

n.接种疫苗，种痘

参考例句：

• Vaccination is a preventive against smallpox.种痘是预防天花的方法。
• Doctors suggest getting a tetanus vaccination every ten years.医生建议每十年注射一次破伤风疫苗。

3 remains   

n.剩余物，残留物；遗体，遗迹

参考例句：

• He ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
• The remains of the meal were fed to the dog.残羹剩饭喂狗了。

4 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

5 migration   

n.迁移，移居，（鸟类等的）迁徙

参考例句：

• Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
• He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。

6 epidemics   

n．流行病

参考例句：

• Reliance upon natural epidemics may be both time-consuming and misleading. 依靠天然的流行既浪费时间，又会引入歧途。
• The antibiotic epidemics usually start stop when the summer rainy season begins. 传染病通常会在夏天的雨季停止传播。

7 onset   

n.进攻，袭击，开始，突然开始

参考例句：

• The drug must be taken from the onset of the infection.这种药必须在感染的最初期就开始服用。
• Our troops withstood the onset of the enemy.我们的部队抵挡住了敌人的进攻。

8 sporadic   

adj.偶尔发生的 [反]regular；分散的

参考例句：

• The sound of sporadic shooting could still be heard.仍能听见零星的枪声。
• You know this better than I.I received only sporadic news about it.你们比我更清楚，而我听到的只是零星消息。

9 ebb   

vi.衰退，减退；n.处于低潮，处于衰退状态

参考例句：

• The flood and ebb tides alternates with each other.涨潮和落潮交替更迭。
• They swam till the tide began to ebb.他们一直游到开始退潮。

10 densely   

ad.密集地；浓厚地

参考例句：

• A grove of trees shadowed the house densely. 树丛把这幢房子遮蔽得很密实。
• We passed through miles of densely wooded country. 我们穿过好几英里茂密的林地。

11 investigator   

n.研究者，调查者，审查者

参考例句：

• He was a special investigator for the FBI.他是联邦调查局的特别调查员。
• The investigator was able to deduce the crime and find the criminal.调查者能够推出犯罪过程并锁定罪犯。

12 swell   

vi.膨胀，肿胀；增长，增强

参考例句：

• The waves had taken on a deep swell.海浪汹涌。
• His injured wrist began to swell.他那受伤的手腕开始肿了。

13 densities   

密集( density的名词复数 )； 稠密； 密度（固体、液体或气体单位体积的质量）； 密度（磁盘存贮数据的可用空间）

参考例句：

• The range of densities of interest is about 3.5. 有用的密度范围为3．5左右。
• Densities presumably can be probed by radar. 利用雷达也许还能探测出气体的密度。

14 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

15 annually   

adv.一年一次，每年

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。
• They celebrate their wedding anniversary annually.他们每年庆祝一番结婚纪念日。

16 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。