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The London Underground: Genes, Germs and Geography

There is a saying that you can take a boy out of a village, but you can never take a village out of a man. I was born in England, and spent a portion of my childhood in India, and now live in New Zealand (and teach in Australia), so I feel a sense of affinity to all these places and they all feel like home. I tend to come back to the UK mostly for medical research or literary festivals these days, and I love these trips.

Living in Auckland, which must have the worst public transport of any major international city, I miss the efficiency of a London underground. Everyone asks me why on earth I still have the London Underground App on my phone when I don’t live in London!

But perhaps like the village analogy above, one cannot take the science out of a scientist. My latest book, The Genetics of Health is to do with how genes shape our health, and how our actions and diets modify our gene-expressions, so as a scientist I thought I’d take a look at the genes and germs that commute on the Tube (not the two-legged variety) in that context.

Genes: Genomics is useful in studying trains and public transport because we can see the DNA of different bacteria lurking there. Also, as different body tissues can be differentiated by genetic analysis, researchers can even tell which body part the organisms originated from.

A few years ago, an 18-month study of the New York subway system tried to look at mapping microbes using genetic analysis. This study ended rather embarrassingly as researchers thought the DNA profiles included bubonic plague and anthrax, claims that were debunked by the CDC. However, this got other subway systems in the world interested. Technology improved. Studies followed in Sweden, Hong Kong, London and Boston. The Boston T is the United States' oldest subway system, dating back to a single street car commissioned in 1897.

In Boston, researchers spent three days taking swabs from seats, seatbacks, walls, poles and hanging grips on train cars on different lines, and they also swabbed the touchscreens and walls of ticketing machines inside five stations.

Germs: Studies have found very little difference in the pattern of organisms irrespective of locations i.e. bugs also live seem to live in a globalized multi-cultural world. There did not seem to be much ethnic differences, indicating the oneness of humankind. Did they find anthrax or bubonic plague? No (much to the relief of those worried about microscopic jihad).

But researchers did find these kinds of bacterial species: Staphylococcus and Corynebacteria species that live on skin, and are transferred through touch. Micrococcus and Streptococcus from the oral cavity, that tend to spread by people coughing or sneezing. Smaller amounts (fortunately) of Lachnospiracea, Veillonella and Prevotella, from our guts. To the discomfort of some in The Vatican (I’m kidding), they found vaginal microbes, which can be transferred through clothing, on seats (I’m not kidding). They also found some non-human bacteria like Alphaproteobacteria, found in plants, and Sphingomonads from soil. The latter were mostly found on the outdoor touch screens and not inside the train car handrails.

Curtis Huttenhower, an associate professor of computational biology and bioinformatics at Harvard, led the study and plans to conduct further studies to see which microbes are dormant or growing, and aims to specifically study the winter flu season when we normally expect more germ populations. There was an interesting difference, however, between Harvard and Hong Kong – there were more soil-associated bacteria in Hong Kong than in the Harvard study.

Geography: Let’s look at the London Underground. Researchers swabbed 60 surfaces along the 10 busiest tube lines and had samples tested in an independent laboratory. The results: Northern Line, the grubbiest; the Hammersmith and City line, the cleanest.

When researchers studied individual stations, Stratford station is the worst, with an average bacterial count of 1,647 CFU (colony-forming units) and scored poorly both on escalators and touchscreens. Not surprising, do you think? The last time I travelled there I could feel these critters crawling on my skin (possibly only because I’d just read the study results). Bank and Monument stations come in joint second place for germ counts, followed by Victoria, King’s Cross St Pancras and Oxford Circus.

What can we do about this? As a skin doctor, I’d advise the following: Don’t touch your face while on the tube (as most people can cope with invisible infections, but not when displayed on their faces); Don’t eat food with your hands after getting off the train (until you have had a chance to wash your hands). The NHS (the closest thing, in my view, to a broad church in the UK) advises us to wash our hands with soap and water. Or we can carry some alcohol hand gel with us.

P.S: Can you guess the cleanest tube station in London?

Canary Wharf.

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