"超級鼻子"可以嗅出疾病的味道?

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.

疾病總是帶着一些氣味兒，這很正常。但如果能借此及早察覺到疾病，就很有可能及早治療。

Breath, bodily odours and urine are all amazingly revealing about general health. Even the humble 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、體味、尿液，能夠極其準確地預測人的整體健康狀況。 多虧了喉嚨裏的濃濃的阻擋細菌的粘液，我們患了小感冒也會有“味道”。 這些標誌並非對所有人都很明顯，但是一些“超級鼻”對這些氣味很敏感。比如，喬伊米爾恩在她丈夫被診斷出有帕金森之前，就察覺到了他氣味的變化。

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 olfactory receptors. And the human sense of smell is 10,000 times more sensitive than the sense of taste.

人類可以分辨出將近一萬種不同的氣味。這些氣味與空氣中的化學物質結合，被細小的毛髮吸收，讓我們極其敏銳的神經纖維感受到，傳導到鼻子裏的嗅覺接受器裏。而且，人類的嗅覺比味覺靈敏一萬倍。

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 sniff out cancers, for example, was first published about 10 years ago. And there have been many tales of dogs repeatedly sniffing an area of their owner's body, only for it to turn out to be hiding a they are smelling are the "volatile molecules" given off by cells when they become cancerous. Some studies suggest dogs can be 93% accurate. Others suggest they can detect very small tumours before clinical tests can. And yet more studies have produced mixed results.

不過，就像我們經常開玩笑說的那樣，狗鼻子更靈。它們能嗅出的味道數量是人類的四倍，這使得我們能對很多種疾病建立一個早期警示系統，比如，十年前發表的一個研究表明：狗狗能嗅出癌症的味道。據說，如果主人某個部位有隱藏腫瘤，狗狗會不停地嗅那個地方，嗅癌變細胞散發出的“揮發性微粒”。有些研究表明，狗狗的嗅覺93%的機率是準確的。還有一些研究表明它們能比臨牀檢測更早的感知到小腫瘤。但是還有很多研究發現了混合的結果。

Does cancer smell?

癌症有氣味嗎？

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.

米爾頓凱恩斯大學醫院的一小支隊伍最近開始收集人類氣味的樣本來測試狗狗鑑定前列腺癌的能力。這些病人都患有一些症狀，比如排尿困難或尿流變化，這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.

此項研究和醫院發展的領頭人羅威納弗萊徹表示，經過醫療檢測犬項目訓練的狗能挑選出癌症的氣味。接着，臨牀檢測能夠顯示狗狗的判斷是否正確。以後將有可能將狗用在這類的用途上，這一點是意義深遠的，即使在每臺手術時都配一隻狗不太現實。

"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."

她說：“我們希望有一天，每個醫生的桌子上都能有一個電子機器，通過嗅覺來檢測就醫的人是否得了病，但是我們首先要知道狗嗅的是什麼。”

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.

這就是問題關鍵了。狗狗不能告訴我們他們在嗅什麼，但是科學家相信，即使有些癌症的氣味非常相似，但不同癌症氣味還是有區別的。

Electronic noses

電子鼻

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.

通過實驗室測試去探索這些訓練有素的狗狗所嗅到的東西可以幫助“電子鼻”的發展，以此來辨別氣味。這可能在將來會促進診斷測試的發展。

The potential for using smell to test for a wide range of diseases is huge, Ms Fletcher says. Bacteria, cancers and chronic 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.

弗萊徹女士說，使用氣味來診斷很多疾病的可能性很大。細菌、癌症、慢性病都有它們獨特的氣味，這些氣味可能對極其敏感的人類來說都不太明顯，但是對狗狗來說卻很明顯。在將來，這些疾病的氣味可能會作爲國家篩選項目的基礎，或者去測試可能患癌症的特殊年齡羣裏的每個人。

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 eligible to be trained provided they are keen on searching and hunting. Whatever their breed or size, it's our four-legged friend's astounding sense of smell which could unlock a whole new way of detecting human diseases.

但是，目前英國只有不到20只狗狗受到過檢測癌症的訓練。越多的訓練意味着越多的時間和資金。不過，從積極的一面來說，所有對搜尋和追捕有興趣的狗狗都有資格接受訓練，不論他們是什麼品種、大小如何，畢竟，是他們驚人的嗅覺爲我們檢測人類疾病的新道路提供了可能。