Why Lettuce Is Always Making People Sick
Why Lettuce Is Always Making People Sick
为什么生菜总是让人“病从口入”？
Salad is usually synonymous with healthy eating. Except now, as the US grapples with an expanding outbreak of cyclosporiasis that’s sickened more than 7,100 people in Michigan alone, likely caused by iceberg lettuce supplied by Taylor Farms. 沙拉通常是健康饮食的代名词。但现在情况却并非如此，美国正面临一场不断扩大的圆孢子虫病（cyclosporiasis）疫情，仅在密歇根州就有超过 7100 人患病，这很可能是由 Taylor Farms 供应的圆生菜（iceberg lettuce）引起的。
In fact, leafy greens are frequently implicated in instances of foodborne illness. There was a 2022 multistate E. coli outbreak tied to romaine served on Wendy’s sandwiches and 173 cases of norovirus linked to Illinois eatery D.C. Cobb’s. In 2021, BrightFarms recalled packaged salad greens sold in several states after 31 people got salmonella. And in 2019, a total of 167 people were infected with E. coli after eating romaine harvested from the Salinas Valley region in California. This isn’t even the first cyclospora outbreak linked to lettuce: In 2020, Fresh Express salad kits were linked to more than 700 cases of people afflicted with the parasite. 事实上，绿叶蔬菜经常与食源性疾病挂钩。2022 年，美国多个州爆发了与温迪汉堡（Wendy’s）所用罗马生菜有关的大肠杆菌疫情，伊利诺伊州的 D.C. Cobb’s 餐厅也曾发生过 173 例诺如病毒感染事件。2021 年，在 31 人感染沙门氏菌后，BrightFarms 召回了在多个州销售的包装沙拉菜。2019 年，共有 167 人因食用加州萨利纳斯谷（Salinas Valley）地区收获的罗马生菜而感染大肠杆菌。这甚至不是第一次与生菜有关的圆孢子虫疫情：2020 年，Fresh Express 沙拉包就曾导致 700 多人感染该寄生虫。
The Centers for Disease Control and Prevention estimates that produce is responsible for almost half of the reported foodborne illness cases, with leafy vegetables topping the list. So what is it that makes lettuce a major source of America’s foodborne tummy troubles? 美国疾病控制与预防中心（CDC）估计，农产品导致了近一半的食源性疾病报告病例，其中绿叶蔬菜位居榜首。那么，究竟是什么让生菜成为美国食源性肠胃问题的“重灾区”呢？
One big reason is simply because lots of people eat it. Lettuce is the second-most-consumed vegetable in the US behind potatoes. (The latest outbreak ensures potatoes will remain the king of US veggies. Plus, french fries.) Wraps, subs, tacos, you name a fast food sandwich and it’s almost certainly got lettuce on it. Salad-slinging chains are fixtures across the US. Grocery store coolers are stocked with salad kits, on top of the unadorned heads of iceberg lettuce and containers of spinach. 一个主要原因很简单：吃的人太多了。生菜是美国消费量第二大的蔬菜，仅次于土豆。（最近的疫情确保了土豆将继续稳坐美国蔬菜之王的宝座，毕竟还有炸薯条。）卷饼、潜水艇三明治、塔可饼，随便点一种快餐三明治，里面几乎肯定有生菜。售卖沙拉的连锁店遍布美国各地。杂货店的冷藏柜里不仅摆满了未加工的圆生菜和盒装菠菜，还堆满了各种沙拉包。
Those ready-to-eat salads and blends of spring mix pose a particularly acute risk because they contain multiple types of leafy greens, which can come from different farms and locations. If one type of lettuce in the mix is contaminated, it can contaminate the whole bag. And because that contaminated lettuce gets packaged into lots and lots of bagged salad, it has the potential to spread germs far and wide. 那些即食沙拉和混合嫩叶菜（spring mix）构成了特别严重的风险，因为它们包含多种绿叶蔬菜，这些蔬菜可能来自不同的农场和产地。如果混合菜中的某一种生菜受到污染，整袋产品都可能被污染。而且，由于这些受污染的生菜会被分装进大量的袋装沙拉中，病菌就有可能大范围传播。
How lettuce is grown can also expose it to a wide array of pathogens. A 2025 study by researchers at Cornell University who studied E. coli outbreaks in romaine lettuce found that a lot of contamination originates from irrigation with untreated surface water applied through overhead spray irrigation systems. There are ways to lower that risk, including switching to irrigation systems that do not directly touch the leaves, but that would require upgrades and downtime. 生菜的种植方式也可能使其接触到多种病原体。康奈尔大学的研究人员在 2025 年对罗马生菜大肠杆菌疫情的研究发现，许多污染源于使用未经处理的地表水，并通过喷灌系统进行灌溉。降低这种风险的方法是有的，包括改用不直接接触叶片的灌溉系统，但这需要进行设备升级并停工。
Lettuce’s satisfying crunch is also what makes it prone to pesky pathogens. Since it’s eaten raw—really, who wants wilted lettuce?—there’s no opportunity to cook off any lingering contaminants. Like other raw fruit and produce, leafy greens don’t go through what’s known as a “kill step”—heating, pasteurization, or freezing—which is designed to eliminate pathogens during the food manufacturing process. 生菜令人满意的爽脆口感也是它容易滋生病原体的原因。由于它是生吃的——毕竟谁会想吃蔫掉的生菜呢？——因此没有机会通过烹饪来消灭残留的污染物。与其他生鲜水果和农产品一样，绿叶蔬菜没有经过所谓的“杀灭步骤”（如加热、巴氏杀菌或冷冻），而这些步骤旨在食品生产过程中消除病原体。
The texture of lettuce is an additional factor in its ability to spread disease. “Many lettuce types have a lot of crevices and folds,” says Jeanne Marrazzo, CEO of the Infectious Diseases Society of America. “It’s very easy for these tiny pathogens to get in there.” 生菜的质地是其传播疾病的另一个因素。美国传染病学会（IDSA）首席执行官珍妮·马拉佐（Jeanne Marrazzo）表示：“许多生菜品种有很多缝隙和褶皱，这些微小的病原体很容易藏在里面。”
Even prewashing procedures at manufacturing facilities don’t always remove microbes, which can cling tightly to leaves. In the case of cyclospora, the parasite has thick outer walls, making it highly resistant to most food sanitizers. Experts say vigorous washing that involves scrubbing is the best way to get rid of cyclospora. “If you don’t wash these products well, you’re going to end up ingesting whatever is on the lettuce,” says Amira Roess, an epidemiologist at George Mason University. 即使是生产设施中的预清洗程序也并不总能去除微生物，因为它们会紧紧附着在叶片上。以圆孢子虫为例，这种寄生虫有厚厚的外壁，对大多数食品消毒剂具有很强的抵抗力。专家表示，通过擦洗进行彻底清洗是去除圆孢子虫的最佳方法。乔治梅森大学的流行病学家阿米拉·罗斯（Amira Roess）说：“如果你不把这些产品洗干净，最终就会把生菜上残留的所有东西都吃进肚子里。”