13 October 2011 Last updated at 20:55 ET

Now wash your hands - and your mobile

It is the sort of news story that will have left many feeling queasy over their breakfast cereal - a study which suggests one in six mobile phones is contaminated with faecal matter.

Researchers at the London School of Hygiene and Tropical Medicine and Queen Mary, University of London took nearly 400 samples from mobile phones and hands in 12 British cities.

They found 16% of phones and 16% of hands harboured E. coli (Escherichia coli), bacteria which inhabit the human intestines.

The largest proportion of contaminated phones was in Birmingham (41%) while Londoners were caught with the highest proportion of E. coli present on hands (28%).

But the sample size in each city was small, so the variations between them could be a statistical anomaly.

However Dr Val Curtis, from the London School of Hygiene says the study showed clear differences between north and south.

"We found the further north we went the more hands and phones were likely to be contaminated. It could be the bugs survive better in colder and wetter conditions or it might be that people wash their hands less."

I explained to Dr Curtis that such comments were unlikely to win her friends in Glasgow and Liverpool - two of the cities where samples were taken.

But she brushed this aside explaining that after a similar survey three years ago she was advised not to hang around Newcastle.

Archers warning

Most strains of E. coli found on the hands and phones are not likely to cause major ill-health, although listeners of "The Archers" will know that Clarrie Grundy became an unwitting carrier of the bacteria, leading to a number of children being hospitalised in the fictional county of Borsetshire.

Dr Curtis explained that they were using E. coli as a marker for the presence of faecal matter.

She said: "Campylobacter and Salmonella bacteria are much more likely to cause a gastric infection and could easily be passed on through faecal contamination."

So we are talking about poo, excrement - on mobile phones and fingers.

Hand washing technique

Why do so many people clearly not wash their hands with soap after a visit to the toilet? Perhaps they do, but are simply doing it wrong.

I remember having correct hand-washing technique described to me by the virologist Professor John Oxford.

He thought people didn't wash thoroughly enough, or long enough - two verses of Happy Birthday to you were suggested.

Perhaps there is also a confusion in some people's minds about dirt and germs. After all, there is plenty of research suggesting dirt can be good for you.

Since the late 1980s the "hygiene hypothesis" has argued that the lack of early childhood exposure to some germs may be linked to the rise in allergic diseases, by suppressing the development of the immune system. It's a much-debated theory.

But while letting your children - or your husband - play in the dirt may well be ok, they still need to wash their hands after the toilet. Or after handling raw meat and poultry.

Big killer

You simply have to look to the developing world to see the devastating effects of poor hygiene. Diarrhoeal disease remains one of the world's biggest killers.

While hand-washing may help prevent a nasty stomach bug here, in poorer countries it can save lives.

The survey from the London School of Hygiene and Tropical Medicine is timed to publicise Global Handwashing Day on 15 October.

It is an annual event which promotes hand-hygiene, the cheapest and most effective way of preventing infection by bacteria and viruses.