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There's usually a laundry list of dos and don'ts that people can expect to hear when they're pregnant.
怀孕的人总会听到一长串的注意事项。
Don't eat fish, don't drink caffeinated beverages and they don't always tell you why.
不能吃鱼，不能喝含咖啡因的饮料，还不告诉你为什么不能。
One of the most oddly specific-sounding ones is a moratorium on soft cheeses.
其中一个听起来最奇怪、最具体的禁令是不能吃软质奶酪。
And there's actually an extremely good reason for it, although the focus shouldn't necessarily fall on Camembert.
这其实有一个很好的理由，虽然重点不应该落在卡蒙贝尔奶酪上。
A number of processed foods, including but not limited to soft cheeses,
很多加工食物，包括但不限于软质奶酪，
can harbor the infectious bacterium Listeria and it's a serious danger to fetuses.
都可能携带传染性李斯特菌属，这种细菌对胎儿有严重危害。
Listeria monocytogenes is a common bacterium found in a huge variety of places,
单核细胞增多性李斯特氏菌是一种常见的细菌，在很多地方都有发现
including water, soil, raw produce, processed foods and even feces.
包括水中、土壤、原料产品、加工食物甚至是排泄物中。
It's actually a pretty uncommon infection in the general population,
其实在普通人群中，这种感染相当不常见，
but one exception is pregnant people, for whom it's nearly 20 times more common.
但孕妇例外，对她们来说，这种感染要常见近20倍。
A lot of changes happen to your body during pregnancy.
怀孕时，你的身体会发生很多变化。
This includes your immune system, specifically a reduction in cell-mediated immunity.
其中包括你的免疫系统，尤其是细胞免疫的减少。
This system includes multiple defense mechanisms that don't rely on antibodies, instead it's mediated by specialized cells.
这个系统中包括各种不依赖抗体的防御机制，它们是由特殊细胞介导的。
This type of immunity is important for detecting and destroying cells in your body that may be infected with viruses or bacteria.
这种免疫力对检测并摧毁身体中可能感染的病毒或细菌很重要。
Your antibody-based immunity, on the other hand, makes those antibodies in response to viruses or bacteria in the fluid outside of your cells.
另一方面，基于抗体的免疫力会对细胞外液体中的病毒或细菌产生抗体。
But your body shifts away from cell-mediated immunity during pregnancy to allow a tiny human to grow inside of you.
但在怀孕期间，你的身体会远离细胞介导的免疫力，让一个小人在你体内生长。
This ensures those well-meaning immune cells don't detect the fetus and treat it like an unwanted intruder.
这确保那些好心的免疫细胞不会发现胎儿，不会把它当成不受欢迎的入侵者。
Although Listeria infection is far more common in pregnant people, symptoms tend to be very mild.
虽然李斯特菌属感染在孕妇中更常见，但其症状却非常温和。
This is because Listeria is a unique bacterium with a sneaky way of getting around
这是因为李斯特菌属是一种独特的细菌，它鬼鬼祟祟地
that doesn't get your antibody-based immune system all riled up.
不会让你基于抗体的免疫系统完全被激怒。
The bacteria basically trick the cells in your gastrointestinal tract into engulfing them.
这些细菌会诱使你胃肠道中的细胞吞没它们。
Once inside a cell, Listeria multiplies and pushes against the membrane,
一旦进入细胞，李斯特菌属就会繁殖并挤压细胞膜，
eventually pushing straight through into neighboring cells without spending any time in the outside space.
最终直接进入相邻的细胞而不需要在外部空间多做停留。
This means your best defense against Listeria is your cell-mediated immunity.
这意味着你对抗李斯特菌属的最好防御是你的细胞介导免疫。
So it makes sense that there's less of a reaction in a pregnant host.
所以在怀孕的宿主体内反应小是有道理的。
But this sneaky way of spreading also means it can get across the placenta, and this is where it becomes really risky.
但这种鬼鬼祟祟的传播方式也意味着它可以穿过胎盘，在这个地方，它就变成了危险人物。
The human maternal-fetal interface is what nourishes your fetus and protects it from both your immune cells and outside infections.
人类的母胎界面是滋养胎儿，保护它免受免疫细胞和外界感染的地方。
Placental cells have direct contact with maternal blood, so the placenta is very resistant to infections, but not to pathogens like Listeria.
胎盘细胞和孕妇外周血有着直接的联系，所以胎盘对感染有很强的抵抗力，但对像李斯特菌属这样的病原体却没有抵抗力。
And researchers aren't totally sure why yet.
并且研究人员也不完全清楚其原因。
Although Listeria doesn't usually have much of an impact on the pregnant person, it's very dangerous to developing fetuses.
虽然李斯特菌属通常对孕妇没什么影响，但它对正在发育的胎儿却非常危险。
It can cause premature birth or pregnancy loss as well as brain damage, and is often fatal to fetuses and newborns.
它会导致早产或妊娠丢失以及脑损伤，并且对胎儿和新生儿通常是致命的。
We mostly get Listeria infections from contaminated foods, and we can take some steps to limit our exposure to it.
我们大部分人都会从受污染的食物中感染上李斯特菌属，并且我们可以采取一些措施避免接触到它。
Like pasteurization, which eliminates Listeria from dairy products.
比如巴氏灭菌法，它可以消除乳制品中的李斯特菌。
So although you can get it from a variety of things, unpasteurized cheese is definitely on the no-go list.
所以虽然你会从各种各样的东西中感染，但是未经高温消毒的奶酪绝对是不能吃的。
In some parts of the world, including the US, it's actually hard to find unpasteurized cheese.
在包括美国在内的一些地方，实际上很难找到未经高温消毒的奶酪。
But Listeria has also been found in pasteurized soft cheeses thanks to manufacturing issues.
但由于生产问题，在经过巴氏消毒的软质奶酪中也发现了李斯特菌。
Soft cheese gets a lot of attention when it comes to Listeria risk,
软质奶酪在李斯特菌感染风险方面很受关注，
but there's actually a wide range of dairy products, cold meats, and other processed foods that are vulnerable to contamination.
但实际上，有很多乳制品、冷冻肉和其他加工食品都容易受到污染。
Recent outbreaks of Listeria have even been linked to unprocessed foods, like raw sprouts, celery, and melon.
近期的李斯特菌爆发甚至与未加工的食物有关，如生豆芽、芹菜和甜瓜。
Like we said Listeria is super common, and it's also behind the prohibition of stuff like hot dogs and deli meats for pregnant people.
如我们所说，李斯特菌超级普遍，这也是禁止为孕妇提供热狗和肉类熟食的原因。
So to be on the safe side, it might be a good idea to just avoid the deli counter for the duration of pregnancy!
所以为了安全起见，在怀孕期间避开肉类熟食柜台可能是个好主意！
Thanks for asking, and thanks especially to our patrons for supporting this episode.
感谢提问，特别感谢我们的赞助人对本期节目的支持。
Patrons have a chance at getting their questions answered in episodes like this one.
赞助人有机会提问并将问题制成像这样的视频。
So if there's something you're itching to know, consider becoming a patron at patreon.com/scishow.
所以如果你想提问，考虑一下成为我们的赞助人吧。
