In the toilets of a service station, at an undisclosed location along a motorway in middle England, Dr Val Curtis is waging a one-woman war on Britain's filthy hands.

As weary travellers flush, zip and button, an electronic message board on the wall flashes: “Washing hands with soap avoids disease... Is the person next to you washing with soap?”

The amount of soap used in any given period is measured by sensors on the dispensers and, when compared with the number of people that enter the washrooms in the same time, gives a depres- singly accurate picture of modern Britain's slovenliness.

Curtis, the director of the Hygiene Centre at the University of London, a co-founder of the Global Partnership for Handwashing with Soap, and all-round hand-washing aficionado, has not collated the final results yet. But even the most disgusting electronic message she could think of, “Soap it off or eat it later”, has failed to elicit a scrum for the soap. “I think what we need to do next is put up a poster with a big photo of poo on it,” she sighs.

Two years ago, the United Nations declared 2008 to be the International Year of Sanitation. Britain, a nation that has produced sanitation visionaries such as John Snow, who proved that cholera was spread by water, and Edwin Chadwick, who conceived of sewage disposal and piping water into homes, should have been leading the way. Instead, our hands have remained decidedly dirty.

Last month, on Global Handwashing day no less, Dr Curtis caused a stir when she did a swab test of commuters' hands in London, Cardiff, Birmingham Liverpool and Newcastle. The results appeared to show that northerners' hands were dirtier than those of southerners. But beyond the geographic hyperbole, the survey had much more worrying implications than a few angry Geordies. Averaged out, the figures showed that more than one in four Britons had faecal matter on their hands - no matter where they came from. And while the number of men with dirty hands varied between the North and the South, the number of women, often the family food preparers and child carers, remained constant at a startling 30 per cent.

An earlier study carried out by Curtis in Huddersfield, West Yorkshire, found that just 43 per cent of mothers washed their hands after changing their baby's nappy. “We all wash our hands in principle, but in practice, we've all got an excuse,” says Curtis.

According to John Oxford, a professor of virology and the chairman of the UK Hygiene Council, just half the UK population has an understanding of the importance of hand hygiene and too many do not put their knowledge into action. “Hygiene has not been high on the agenda,” Oxford says. “You say you're a professor of hygiene and people tend to think that you're the man who cleans the toilets.”

In an international study of seven countries conducted by the Hygiene Council in May, the UK was found to be the third worst nation for germs after India and Malaysia. The study, which also included Saudi Arabia, South Africa, Germany and the US, found 33 per cent of surfaces in British homes covered in E. coli, faecal matter and other dangerous pathogens spread by dirty hands.

“Most people we interviewed in the UK did not appreciate that we can catch diseases from our hands,” says Oxford. “They didn't realise that hands had anything to do with it.”

But hands have everything to do with it. Research carried out this month in America found that an average hand is home to 150 species of bacteria - comparable to, or even more than are found in the mouth, oesophagus and lower intestine. And womens' hands were found to have 50 per cent more varieties than men due to skin acidity, hormones and hand cream.

The majority of these organisms are harmless; others are not. Britain's 12 million annual cases of norovirus and gastroenteritis, causing projectile vomiting and diarrhoea, the MRSA epidemic in hospitals last winter, and an outbreak of E. coli in Scotland the year before are all down to pathogens on dirty hands.

It is estimated that most of the 120 million common colds contracted each year in the UK are also caused by viruses spread by hands (See Dr Thomas Stuttaford, page 15).

The average child misses one week of school a year due to communicable ill- nesses such as these. In the UK, this equates to an annual 36 million days lost to absenteeism. But the Hygiene Council has found that good hand-washing practices and ready access to the hand sanitiser in school can reduce this figure by almost 50 per cent. Absentee numbers have plummeted at one school, George Watson's College, in Edinburgh after it introduced mandatory hospital-style handwashing for all its pupils in January.

“The bugs that make us sick come from the toilet,” says Curtis. “And the point after going to the toilet when you don't wash your hands is the superhighway moment.”

The germs spread to hotspots such as door handles, light switches, remote controls, basin taps and telephones where other people pick them up. Or a person will infect themselves by putting their fingers in their mouth or rubbing their eyes or nose. Once a bug is inside a person, it will “multiply like crazy and then pump out by the billion at the other end”, says Curtis. A stool from an infected person contains ten billion pathogenic microbes, many of which rise into the air to continue the cycle.

The solution should be simple. Hygiene is cheap soap and water, the experts say, still the most effective method of hand washing. “Hygiene is self-empowering,” says Oxford. “People don't need an expert like me next to them. They can do something about hygiene themselves.”

Guidance issued by the Centre for Disease Control in Atlanta in the US says that a person should sing Happy Birthday twice as they wash their hands. Coughs and sneezes should be directed into elbows rather than hands.

But Curtis believes that the problem of Britain's dirty hands is more complex. “Disgust is a ‘gene' that evolved in our animal ancestors to help us survive and avoid infection,” she says. And out of disgust came hygiene: there is evidence that neanderthals used seashell tweezers to pluck hairs and remove skin parasites, and that woman used the residue of animal fat and ash from roast meat to remove stains.

“A caveman would go to the loo in a field, see and smell what they had done and be disgusted by it, so they would be sure to wipe their hands after,” says Curtis. “Now we live in this beautiful, pristine environment with white tiles on the wall and we do everything to make our poo invisible and unsmellable. We're not feeling the same sense of contamination.”

Our hands are dirty, Curtis concludes, because our toilets are simply too clean.

Germ warfare: the facts

100,000: Average number of bacteria found on one square inch of healthy skin

1,000,000: Number of lives that could be saved in the world each year if everyone washed their hands with soap

One in four: The proportion of British kitchen cloths that harbour the E. coli virus, an indicator of faecal contamination

Two hours: Length of time that some bacteria can remain alive on surfaces after being deposited by hands

20 seconds: The length of time hands should be washed with soap and warm water

30: Number of years added to our average life expectancy in the past century through advances in hygiene