The fact diseases have a smell comes as no surprise - but finding someone or something that can detect them at an early stage could hold huge potential for medicine.

疾病总是带着一些气味儿，这很正常。但如果能借此及早察觉到疾病，就很有可能及早治疗。

Breath, bodily odours and urine are all amazingly revealing about general health. Even the humble¹ cold can give off an odour, thanks to the thick bacteria-ridden mucus that ends up in the back of the throat. The signs are not apparent to everyone - but some super-smellers are very sensitive to the odours. Joy Milne, for example, noticed her husband's smell had changed shortly before he was diagnosed with Parkinson's disease.

呼吸、体味、尿液，能够极其准确地预测人的整体健康状况。 多亏了喉咙里的浓浓的阻挡细菌的粘液，我们患了小感冒也会有“味道”。 这些标志并非对所有人都很明显，但是一些“超级鼻”对这些气味很敏感。比如，乔伊米尔恩在她丈夫被诊断出有帕金森之前，就察觉到了他气味的变化。

Humans can detect nearly 10,000 different smells. Formed by chemicals in the air, they are absorbed by little hairs, made of extremely sensitive nerve fibres, hanging from the nose's olfactory² receptors. And the human sense of smell is 10,000 times more sensitive than the sense of taste.

人类可以分辨出将近一万种不同的气味。这些气味与空气中的化学物质结合，被细小的毛发吸收，让我们极其敏锐的神经纤维感受到，传导到鼻子里的嗅觉接受器里。而且，人类的嗅觉比味觉灵敏一万倍。

But dogs, as the old joke might have had it, smell even better. Their ability to detect four times as many odours as humans makes them a potential early warning system for a range of diseases. Research suggesting dogs' could sniff³ out cancers, for example, was first published about 10 years ago. And there have been many tales of dogs repeatedly sniffing⁴ an area of their owner's body, only for it to turn out to be hiding a tumour⁵.What they are smelling are the "volatile⁶ molecules⁷" given off by cells when they become cancerous. Some studies suggest dogs can be 93% accurate. Others suggest they can detect very small tumours⁸ before clinical tests can. And yet more studies have produced mixed results.

不过，就像我们经常开玩笑说的那样，狗鼻子更灵。它们能嗅出的味道数量是人类的四倍，这使得我们能对很多种疾病建立一个早期警示系统，比如，十年前发表的一个研究表明：狗狗能嗅出癌症的味道。据说，如果主人某个部位有隐藏肿瘤，狗狗会不停地嗅那个地方，嗅癌变细胞散发出的“挥发性微粒”。有些研究表明，狗狗的嗅觉93%的几率是准确的。还有一些研究表明它们能比临床检测更早的感知到小肿瘤。但是还有很多研究发现了混合的结果。

Does cancer smell?

癌症有气味吗？

At Milton Keynes University Hospital, a small team has recently begun to collect human urine samples to test dogs' ability to detect the smell of prostate cancer. The patients had symptoms such as difficulty urinating or a change in flow, which could turn out to be prostate, bladder or liver cancer.

米尔顿凯恩斯大学医院的一小支队伍最近开始收集人类气味的样本来测试狗狗鉴定前列腺癌的能力。这些病人都患有一些症状，比如排尿困难或尿流变化，这可能是前列腺癌或膀胱癌或肝癌的前兆。

Rowena Fletcher, head of research and development at the hospital, says the role of the dogs - which have been trained by Medical Detection Dogs - is to pick out samples that smell of cancer.

此项研究和医院发展的领头人罗威纳弗莱彻表示，经过医疗检测犬项目训练的狗能挑选出癌症的气味。接着，临床检测能够显示狗狗的判断是否正确。以后将有可能将狗用在这类的用途上，这一点是意义深远的，即使在每台手术时都配一只狗不太现实。

"We hope one day that there could be an electronic machine on every GP's desk which could test a urine sample for diseases by smelling it," she says. "But first we need to pick up the pattern of what the dogs are smelling."

她说：“我们希望有一天，每个医生的桌子上都能有一个电子机器，通过嗅觉来检测就医的人是否得了病，但是我们首先要知道狗嗅的是什么。”

And that's the key. Dogs can't tell us what their noses are detecting, but scientists believe that different cancers could produce different smells, although some might also be very similar.

这就是问题关键了。狗狗不能告诉我们他们在嗅什么，但是科学家相信，即使有些癌症的气味非常相似，但不同癌症气味还是有区别的。

Electronic noses

电子鼻

Lab tests to understand what these highly-trained dogs are smelling could then inform the development of 'electronic noses' to detect the same molecules. These might then give rise to better diagnostic tests in the future.

通过实验室测试去探索这些训练有素的狗狗所嗅到的东西可以帮助“电子鼻”的发展，以此来辨别气味。这可能在将来会促进诊断测试的发展。

The potential for using smell to test for a wide range of diseases is huge, Ms Fletcher says. Bacteria, cancers and chronic⁹ diseases could all have their own odour - which may be imperceptible to only the most sensitive humans, but obvious to dogs. It may be possible in the future to use disease odours as the basis for a national screening programme or to test everybody at risk of a certain cancer in a particular age group.

弗莱彻女士说，使用气味来诊断很多疾病的可能性很大。细菌、癌症、慢性病都有它们独特的气味，这些气味可能对极其敏感的人类来说都不太明显，但是对狗狗来说却很明显。在将来，这些疾病的气味可能会作为国家筛选项目的基础，或者去测试可能患癌症的特殊年龄群里的每个人。

However, there are fewer than 20 dogs in the UK trained to detect cancer at present. Training more will take more funding and time. On the positive side, all dogs are eligible¹⁰ to be trained provided they are keen on searching and hunting. Whatever their breed or size, it's our four-legged friend's astounding¹¹ sense of smell which could unlock a whole new way of detecting human diseases.

但是，目前英国只有不到20只狗狗受到过检测癌症的训练。越多的训练意味着越多的时间和资金。不过，从积极的一面来说，所有对搜寻和追捕有兴趣的狗狗都有资格接受训练，不论他们是什么品种、大小如何，毕竟，是他们惊人的嗅觉为我们检测人类疾病的新道路提供了可能。