The remaining countries are Afghanistan, India, Nigeria and Pakistan.

这四个剩余国家是阿富汗、印度、尼日利亚和巴基斯坦。

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Today polio is endemic in only four countries: Afghanistan, India, Nigeria and Pakistan.

今天，小儿麻痹症只有在四个国家存在：阿富汗、印度、尼日利亚和巴基斯坦。

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The poliovirus is restricted to a handful of areas in these countries (Afghanistan, India, Nigeria and Pakistan).

在这些国家(尼日利亚、印度、巴基斯坦和阿富汗)，脊髓灰质炎病毒局限于少数地区。

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Officials say similar vaccination campaigns are planned this year in India, Nigeria and Pakistan.

VOA: special.2010.01.18

Afghanistan,India,Pakistan,Nigeria, the Democratic Republic of Congo and Ethiopia also had increases.

VOA: special.2010.04.14

The campaign is focusing on Pakistan, Afghanistan,India and Nigeria - the four countries where the disease remains.

VOA: standard.2010.08.02

In 2012, there were fewer than 225 cases and the spread of the virus has to be stopped in only three countries: Afghanistan, Nigeria and Pakistan.

WSJ: Bill Gates and Michael Bloomberg: Our Plan to Eradicate Polio

In Afghanistan, Nigeria, and Pakistan, vaccinators travel long distances across difficult terrain, and some parents won't allow their children to be vaccinated.

WSJ: Bill Gates and Michael Bloomberg: Our Plan to Eradicate Polio

Polio, another picornavirus, which exclusively affects humans, has been eliminated from nearly every country in the world, although it stubbornly persists in Nigeria, Pakistan and Afghanistan.

BBC: Synchrotron yields 'safer' vaccine