By Tom Geoghegan
BBC News Magazine
Rail safety experts are investigating the cold and flu risks faced by commuters packed on trains. With the flu season upon us, we ask experts what does lurk among bus, rail and Tube passengers?
Full marks for sneezing etiquette....
It's been a bad news week for those who struggle to work each day on public transport.
First a study claimed it can be more stressful being a commuter than a fighter pilot.
Now BBC News has learnt the Rail Safety Standards Board is investigating the impact of overcrowding on trains and the Tube, including how much passengers share bugs.
No scientific research has yet been done on this but experts in virology believe poor ventilation and a lack of space can make some forms of public transport a fertile breeding ground. However there is a strong argument this fear may be over-hyped.
"The London Underground must be an absolute goldmine for viruses trying to find someone to spread to because it's so packed," says Dr Rosy McNaught, a consultant in communicable disease control for Sheffield.
"The closer people are packed together and poorer the ventilation, the more likely people close to you will get a face full of it when you sneeze."
Cold and flu viruses travel through the air from a cough or sneeze and get into the body through the mouth or eye. They can also be passed from hand to mouth via carriage handles or straps.
"Airborne transfer is probably more significant in those confined surroundings and if someone coughs in your face and you breathe it in there's probably quite a high chance of transmission of cold or flu," says Charles Penn, professor in microbiology at the University of Birmingham. "That's their natural route of transmission so in close proximity you're breathing in drops from other people's respiratory systems."
However, at least Tube trains have opening windows - at the end of each carriage. On the railways, much of the new rolling stock uses air-conditioning, which re-circulates air. Bus passengers have also complained that new models are overheated and lack ventilation because of smaller windows.
Consultant biologist Colin Fink says better ventilation and the confidence to open windows, where possible, is the key to tackling this. Although not aware of any scientific studies, he thinks there is undoubtedly a great deal of transfer of respiratory illnesses on overcrowded transport, especially in conditions of high humidity.
HOW TO CATCH A COLD...
Respiratory viruses like colds and flus are spread by droplets from coughs and sneezes
Some droplets are invisible but can still be inhaled through the mouth or passed through the eyes
Transmission can also happen when someone sneezes or coughs into their hands and then touches a rail or strap before someone else
"If you ventilate and keep the humidity down, you reduce the risk of airborne viruses, and persistence of organisms on surfaces so it is always better to have a well-ventilated cool bus rather than a fuggy and warm one.
"Some long distance trains these days are air-conditioned and unless the system is perfectly maintained this creates conditions of greater humidity. I am not aware that the train companies think about the potential for cross infection.
"The take-home message is people should keep windows open on transport so there's a flow-through of fresh air. No one wants to be the first to open the window as this may be seen as an inconvenience to other passengers."
The London Transport Users Committee says anecdotal evidence suggests passengers are getting colds from these conditions so it would be interested to hear the results of the investigation.
But before commuters dash for the mask (and one expert recommended a full facial respirator as the only virus-proof measure), there is cause for optimism.
...AND HOW TO PREVENT ONE
Open bus or train windows to increase ventilation and reduce humidity
Avoid cramped spaces if possible
Practise coughing etiquette - use a hanky or a disposable tissue
If you have a virus, don't travel
Wash your hands when you get to work and don't touch your mouth before doing so
The Health Protection Agency says there is no indication that passengers in London and the South East - where public transport is more crowded - suffer more respiratory illnesses than other parts of the UK.
And two items of research indirectly related to this area suggest the risks may be over-hyped.
University students have been found to suffer colds and flus more in autumn than spring. This has been interpreted as meaning the overriding factor is the arrival of new people living close together, rather than public transport which is constant all year round.
And the infection risk of air-conditioning may not be as high as feared. A study by the Air Transport Association of America claims there is no added risk due to filters. And in cases where a long-haul passenger has been identified with tuberculosis, no other passengers on board are known to have caught it.
Plus, there is a simple step passengers can take to minimise the risk.
"Coughing etiquette or respiratory hygiene - coughing into a hanky - sounds a bit like common sense but it works and it will reduce the spread," says Ms McNaught. "And just think 'Do I need to go into a public place and expose everyone else to my germs?'"
Some of your comments appear below.
My cycle had to go for a service a while ago and I use the DLR for a week - I came down with something very unpleasant. I save £1000 in travel but the best feature of all - I get a guaranteed seat!
As a former bus driver of 10 years, I can honestly say that I have not suffered from colds or flu any more frequently than anyone else. As an aside, the advice to open bus windows makes sense, but in reality I have witnessed passengers coming to blows over a window being opened at this time of year.
Pete, Flintshire, Wales
Here in Japan, not only do people wash their hands every time they return home, they also gargle, often with a solution of diluted iodine. People also wear cotton face masks either to keep others from being exposed to their germs or to prevent being exposed to the germs of others.
It may surprise the general public to know that catching cold or flu viruses, from breeding grounds such as the train or tube, is a an efficient means of immunising vast numbers of people. Once a viurs is transmitted to a new host, the host mounts an immune response which should (in theory at least) protect from further infection.
Dr Terry Guthrie, England
People accuse me of being paranoid or touchy when I complain at their lack of coughing etiquette. There's too much of this behaviour these days. Aren't people taught the importance of it, or do they simply have no regard for anyone else?
Dave Robertson, England
Had my flu shot in late September, so far so good. Last year a woman coughed directly in my face and I was sick for weeks. People can be quite ignorant about this. Washing hands regularly every day is good.
J Sims, UK
Since I have stopped using trains to get to work I have had less colds and feel much healthier.
I can't believe there really are people being paid good money to make a study of this nature.
I am not a doctor or a scientist but I can see that any germ will spread amoung a load of people crammed into an unventilated bus or train.
Gareth, Sussex, England
...and with the higher than inflation 4 percent rise in prices, rail experts will next week investigate whether rail crashes cause injuries. I guess it keeps people in work....
Steve, E Yorks
Ever since reading about the risk of transmission of the cold virus through touch on the BBC website last year, I have been a fanatical handwasher! And I am pleased to report that it does work. I have only had one bad cold in the past 2 years and I am certain that it is for this reason.
Tom Amos, London,uk
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