Now scientists find that those with one type of risky gene may also need to catch a virus to trigger the disease.

如今，科学家们发现拥有某一类型这种基因的人或许感染上一种病毒后才会引发克罗恩病。

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In any given year, between 5% and 20% of Americans can catch the flu, depending upon the strength of a particular flu virus and other factors, the CDC says.

疾病控制预防中心称，每年大约有5% - 20%的美国人会患上流感，具体比例取决于流感病毒的种类及其他因素。

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Merely being exposed to a new cold virus, however, is not enough for a person to catch a cold, since a strong immune system can successfully fight off some new viruses.

然而，仅仅是接触到一种新的感冒病毒并不足以导致一个人患感冒，因为强壮的免疫系统能够成功地战胜一些新病毒。

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The new study shows that happiness spreads through social networks like an emotional virus - a virus people would be happy to catch.

VOA: special.2009.01.21

The Virus Bulletin tests try to catch out anti-virus software with a variety of malicious programs including bots and worms known to be spreading online, file infectors, polymorphic and macro viruses.

BBC: NEWS | Technology | Windows 'fails' active virus test

Mexico could catch a break if the SARS virus persists or spreads in Asia.

FORBES: Magazine Article

Measles is caused by a virus spread in droplets and is easy to catch if you haven't been vaccinated.

BBC: 'Death risk' in Swansea measles outbreak