数百万年以来，许多微生物与人类形成一种共生共栖的关系，就像我们的“老朋友”一样;如果我们将某种微生物连根拔除，就等于错过了人体进化历程中的一个关键环节。

　　"The vast majority of microbes are harmless. There are only a few dozen that can cause lethal infections," says Thomas McDade, director of the Laboratory for Human Biology Research at Northwestern University.

　　“绝大多数微生物都是无害的，只有几十种微生物会引发致命感染。”美国西北大学人体生物研究实验室主任麦克·戴德说道。

　　There are other dangers lurking in muddy water and animal feces. Nearly 70% of the 8.8 million deaths of children under age 5 world-wide in 2008 were caused by infectious diseases, most frequently pneumonia, diarrhea and malaria, according to an analysis in the Lancet last week.

　　但脏水和动物排泄物也潜藏着其他一些危险。英国医学杂志《柳叶刀》2010年五月中旬发表的一篇分析报告称，在2008年全球880万5岁前夭折的孩子中，有近70%死于感染性疾病，最常见的是肺炎、痢疾和疟疾。

　　Scientists are still working on ways to separate good germs from bad ones; in the meantime, they have a few insights: Studies have shown that children who grow up with household pets have fewer allergies and less asthma than those who don't.

　　科学家仍在寻找办法把好的微生物与坏的微生物区分开来，在此过程中，他们有了几点深入发现。研究表明，从小和家庭宠物一起长大的孩子患过敏症和哮喘病的几率较低。

　　Michael Bell, an infectious disease specialist and deputy director of Healthcare Quality Promotion at the Centers for Disease Control and Prevention, says that people should be vigilant about wound care since bacteria can cause problems if they get into the blood stream, and he still advocates hand-washing. "If you're not doing it 10 times a day, you're probably not doing it enough," he says.

　　美国疾病控制与预防中心医疗质量改进部副主任及感染病专家贝尔说，人们应该警惕伤口感染，因为一旦病毒侵入血液，就会造成各种问题。他还是提倡人们勤洗手。“一天至少要洗10次手。”贝尔说。

　　But he and other experts say that regular soap and water are fine in most cases. Sterilizing hands is critical mainly for health-care workers and in hospitals, where disease-causing germs are prevalent and can easily spread.

　　不过，他和其他一些专家表示，在大多数情况下，洗手用普通的肥皂和水就行了。手部消毒主要适用于医疗工作者以及医院场所内，因为医院里的致病微生物较多，而且容易传播开来。