Does frequent hand-washing reduce colds? Yes. A simple hand-washing program among US Navy recruits almost halved the number of respiratory infections they suffered.

It is well-known that frequent hand-washing by hospital staff has a significant impact on infections picked up by their patients.

However, there have been few research studies which clearly demonstrate how similar practices can protect ordinary people in the community.

However, the Great Lakes Recruit Training Command Center in Illinois introduced their own programme of hand-washing.

Recruits were ordered to wash their hands at least five times a day, installing liquid soap dispensers at the side of all sinks on the base and halting the practice of insisting that sinks be dry and clean during snap inspections.

Navy recruits who participated in "Operation Stop Cough" were monitored by Dr Margaret Ryan over the following year.

In 1997 and 1998 illness rates with respiratory tract infections such as coughs were 45% lower for those who took part in the initiative.

Preventing even minor illnesses of this kind is a key concern for the military.

In the US, respiratory illnesses are the most common cause of lost time from duty for young adults.

The military authorities have in the past tried everything from dust suppression and antibiotics to ultraviolet radiation and disinfectant vapours to prevent them.

Viral outbreak

Dr Ryan said hand-washing, while it did not reduce the number of recruits who had to be hospitalized due to respiratory infections, may have reduced the impact of a viral outbreak in autumn 1997.

Dr Joel Gaydos, from the US Defense Department's Global Emerging Infections Surveillance and Response System, said that hand-washing should be valued alongside vaccination as a way of cutting infections.

He said that in offices, the fact that hands do not get visibly soiled means that people are less likely to wash them, even before meals.

"Re-emphasising hand-washing in our daily lives may provide significant benefits with little effort or cost, especially during the respiratory disease season."

In the UK, the Public Health Laboratory Service is closely involved with projects to improve hospital hygiene and cut acquired infections - which cost many lives, and millions, to the NHS each year.

A spokesman said that it was commonsense that frequent hand-washing cut both respiratory and gastro-intestinal infections, even though few studies could bear this out.

"We know viruses can survive outside the body for some time, so it's a good idea to wash your hands, especially if you have some sort of infection yourself."