In late 2006, something strange began to happen to America's honeybees. Colonies that were once thriving suddenly went still, almost overnight. The worker bees that make hives run simply disappeared, their bodies never to be found. Over the past couple of years, nearly one-third of all honeybee colonies have collapsed this way, which led to a straightforward name for the phenomenon: colony collapse disorder (CCD).

This might seem like little more than a tantalizing mystery for entomologists, except for one fact: honeybees provide $15 billion worth of value to U.S. farmers, pollinating crops that range from apples to avocados to almonds. Any number of possible causes for CCD have been put forward, from bee viruses to parasites to environmental triggers like pesticides or even cell-phone transmissions. Despite the Department of Agriculture's allotment of $20 million a year for the next five years to study CCD, it's still a mystery — and the bees keep dying. (Read "Why We Should Care About Dying Bees.")

A new study in the Proceedings of the National Academy of Sciences (PNAS) shows that the causes of CCD may be more varied than scientists expect. The bees may be dying not from a single toxin or disease but rather from an assault directed by a collection of pathogens. A research team led by entomologist May Berenbaum at the University of Illinois compared the whole genome of honeybees that came from hives that had suffered from CCD with hives that were healthy. The sick bees exhibited genetic damage that could account for the die-off, and that damage indicated that they might be afflicted with multiple viruses simultaneously. This could weaken them enough to trigger CCD. "It's like a perfect storm," says Berenbaum.

The PNAS team's work was possible only because the honeybee's genome is one of the few animal genomes that scientists have decoded in full. The researchers looked at the genes that were switched on in the guts of sick and healthy bees — the gut being both the place pesticides are detoxified and the main region for immune defense. The technique they used is what's known as a whole-genome microarray, and it's ideal for this kind of sweeping analysis. "It's a really powerful tool that lets us look at all 10,000 honeybee genes at the same time," says Berenbaum. "The causative agents [for CCD] might just leap out."

In the guts of CCD-afflicted bees, the microarray analysis showed unusual fragments of ribosomal RNA. Ribosomes are essentially the protein factories inside cells — they're vital to the health of the cell itself and the larger organism. Berenbaum believes that the presence of those genetic fragments inside the CCD-afflicted bees indicates that they may be under attack by a number of insect viruses — including deformed wing virus and Israeli acute paralysis virus — that damage the ribosomes. "It was the one factor that remained consistently associated with the CCD bees we tested, no matter where they came from or how severe the disorder was," says Berenbaum. "It doesn't have to be a specific virus, just an overload." Once the bees' systems get burdened this way, they are less capable of fighting off any other threat, from pesticides to other environmental causes. (See TIME's video "Bees Without Borders.")

Berenbaum is quick to point out that the microarray analysis is only correlative, meaning that while it can show evidence that certain viruses are present in CCD-afflicted bees, it doesn't reveal exactly what role the viruses play, nor how best to battle them. One approach might be to control infestations by varroa mites, which carry multiple viruses into the hives they attack. The good news is that the disorder may be on the wane, with the Apiary Inspectors of America reporting that deaths from CCD are below 30% for the first time since the crisis began. "The phenomenon seems to be in decline," says Berenbaum. "The most vulnerable populations might have already crashed." American farmers should be thankful; just think of trying to pollinate all those crops by hand.

自2006年末开始，美国蜜蜂接二连三地发生一些奇怪的现象。一度繁盛的蜂群几乎在一夜之间突然消失殆尽。负责筑巢的工蜂不见了踪影， 其尸首更是无处找寻。在过去的几年里，有将近三分之一的蜂群就这样的消失了，为直观起见，人们称这种现象为：蜂群崩溃紊乱（简称CCD）。

若不是基于蜜蜂能为美国农民带来150亿美元产值的收益以及它们能为苹果、鳄梨、杏仁等植物进行受精传粉的事实，昆虫学家们可能会对这种现象不屑一顾。目前人们对蜂群崩溃紊乱的原因做出了种种的猜测，包括像蜜蜂病毒与寄生虫感染，手机辐射传播等环境诱发因素。尽管农业部计划在未来五年时间里每年拨付2000万美元的资金用于研究蜂群崩溃紊乱现象，但它至今仍是一个谜—蜜蜂继续大批死亡。 （请阅读“为什么我们要去关心垂死的蜜蜂。”）

发表在国家科学院（PNAS）学报上的最新研究表明，导致蜂群崩溃紊乱的原因可能要比科学家预期的复杂。即单一的某种毒素或疾病不会是致蜜蜂于死地的凶手，更有可能的是它们遭到了大量病原体的袭击。伊利诺大学昆虫学家巴伦鲍姆领导的研究小组对比了感染有蜂群崩溃紊乱症状的蜜蜂基因组与健康蜂巢的蜜蜂基因组。发现患病的蜜蜂遗传基因有损伤，这些损伤表明，蜜蜂可能曾同时受到过多种病毒的侵袭。而这些入侵的病毒会减弱蜜蜂的免疫力以引发蜂群崩溃紊乱。 “这就像一场完美的风暴，巴伦鲍姆说。

国家科学院的研究结果不无道理，因为蜜蜂的基因组是目前少数动物中科学家们已完全破译的。研究人员使用全基因微阵列分析法技术（这项技术对全方位扫描非常理想）分别观察了患病与健康蜜蜂的内脏基因—因为内脏是蜜蜂免疫防御的主要器官，在观察前它们的内脏都经过农药解毒处理 。“全基因微阵列分析法技术非常好，它能让我们同时对10,000个蜜蜂基因进行分析观察。 “看来蜂群崩溃紊乱的真相就要水落石出了。贝伦鲍姆说。

感染CCD的蜜蜂，用微阵列分析法可以发现其内脏存在不同寻常的核糖体核糖酸碎片。而核糖体是细胞内主要的蛋白质制造厂—它对细胞本身的健康至关重要，同时它还是生物中较大的有机体。贝伦鲍姆认为，感染CCD的蜜蜂内脏存在的这些基因碎片可能是它们曾遭到过大量昆虫病毒的攻击—像畸翅病毒和以色列急性麻痹病毒—它们都能损害核糖体。 “无论病原于何方以及蜂群崩溃紊乱症状怎么严重，我们在检测中都发现了这些不同寻常的核糖体核糖酸碎片与蜜蜂感染CCD有着密切的联系，贝伦鲍姆说。 “虽然它不是一个特定的病毒，但其数量繁多。”一旦蜜蜂的免疫系统超负荷，它们抵抗其他威胁的能力（像农药及其他环境因素）就会减弱。 （见时代视频资料“蜜蜂无国界。”）

然贝伦鲍姆很快指出，微阵列分析法只能用作参考，也就是说，虽然它能显示出感染CCD蜜蜂体内存在着的某种病毒，但它不能确切分析出病毒具有什么样的破坏作用，也不知道该怎样更好地去消灭它们。可选的一种做法就使蜜蜂少遭瓦螨的感染，因为瓦螨它会将多种病毒带入蜂巢。庆幸的是，这种疾病带来的威胁可能会逐步减弱，美国蜂场检疫报告说，情况得到了好转，自危机爆发以来，因感染CCD而死亡的蜜蜂比率首次降到了30%。但贝伦鲍姆说。 “这可能是最脆弱的蜂群已遭严重的摧毁。”美国的农民应该心存感激，试想一下：如果要人工为作物授粉那将会是什么样子呢。