Many experts advise common sense. "We don't want to say to children, 'OK, play by the dirty river bank and catch whatever you can, but we can say there's nothing wrong with kids playing in the dirt. They don't have to live in total sanitation, and they won't die from eating something off the floor. It's probably more healthy than not."
许多专家建议人们凭常识办事。“我们不会对孩子们说：‘好，去肮脏的河边玩吧，想抓什么就抓什么。但可以这样讲，小孩子玩泥巴没什么大不了的，他们不必生活在完全干净的环境中，也不会因为吃掉到地上的东西就死掉。这样说不定会使他们更健康。”
On a small family farm in Mongolia, a rooster struts around little Bayar's bed, a goat drinks from his bathwater and livestock serve as babysitters.
在蒙古国一个家庭小农场里，一只大公鸡在小小的巴亚尔的床边来回踱步，一只山羊过来喝他的洗澡水，周围的家畜就是照料他的保姆。
By contrast, Mari, growing up in high-rise, high-tech Tokyo, and Hattie, whose doting parents live a "green" lifestyle in San Francisco, both have modern conveniences and sanitation.
与此形成鲜明对比的是，玛丽出生在高楼林立的科技之城东京，海蒂的父母将其视为掌上明珠，在旧金山过着“绿色”的生活方式，两个孩子都享受着便捷的现代生活和干净的卫生环境。
Statistically, Mari and Hattie are healthier. Some 42 out of 1,000 children in Namibia, and 41 out of 1,000 in Mongolia die before their 5th birthday; compared with only 8 in 1,000 in the U.S. and only 4 in Japan.
数据显示，玛丽和海蒂的身体更健康。在纳米比亚，每1000个孩子中约有42个在过五岁生日前夭折，蒙古为41个;而在美国和日本，这一数字仅为8个和4个。
Yet the upscale urban infants are at higher risk for some health problems -- including allergies, asthma and autoimmune diseases like Type 1 diabetes, multiple sclerosis and inflammatory bowel disease -- than the babies in the rural developing world.
不过，城市里的宝宝虽然生活条件优越，但与欠发达国家农村地区的宝宝相比，患上某些疾病的风险更高，包括过敏症、哮喘，以及1型糖尿病、多发性硬化和炎症性肠病等自身免疫性疾病。
Now, there's research that suggests there may be a way to get the best of both worlds.
现在，有一项研究认为，也许有一种方法可以拉近两个世界的距离，让彼此取长补短。
According to the "hygiene hypothesis," first proposed in 1989, exposure to a variety of bacteria, viruses and parasitic worms early in life helps prime a child's immune system, much like sensory experiences program his brain. Without such early instruction, the immune system may go haywire and overreact with allergies to foods, pollen and pet dander or turn on the body's own tissue, setting off autoimmune disorders.
根据1989年首次提出的“卫生假说” (hygiene hypothesis)理论，孩子在成长早期如果接触多种病毒、细菌和寄生虫，将有利于其免疫系统的发展，似乎这样能促进大脑对其做出更好的防御准备。反之，如果缺乏这类早期接触，免疫系统就可能出现紊乱，做出过激反应，如对食物、花粉和宠物毛屑过敏等，或者引发人体机理问题，出现自身免疫失调。
Many of these microorganisms evolved symbiotically with humans over millions of years--the so-called "old friends" theory. But where they've been eradicated, a key part of human development has been thrown off.
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。
