Household infection 'spreads easily'

Bacteria and viruses are easily passed on

Everyday household routines can spread infection with remarkable ease, researchers have found.

However, an expert in microbiology has said this does not necessarily mean that people are at risk.

A team from the University of Arizona studied how easy it is to spread disease by actions such as picking up the telephone and turning on taps.

The study focused on two bugs:

• a bacterium called Serratia rubidea - similar to Shigella and E. coli, both of which cause stomach infections
• a bacterial virus called PRD-1 - similar to human viruses that cause sickness such as rotavirus

The researchers measured the proportion of bacteria and viruses passed on to the hand following infection. This is known as the transmission rate.

They found that using a telephone receiver was a particularly effective way to spread infection.

Everyday activities in a contaminated household or workplace could easily result in the transmission of disease

American Society for Microbiology spokesman

The transmission rate from receiver to hand was 39% for the bacteria and 66% for the viruses.

Tap handles also had a high transmission efficiency, of 28% and 34%.

The researchers also found that it is relatively easy to transfer the infections from the fingertips to the lower lip.

Spread of illness

The results suggest that it is extremely easy to spread illness from even the tiniest amount of contamination.

Another potential source of infection

For instance, human stools and nasal mucus contain vast numbers of bugs.

So the researchers calculated that even the tiniest amount of human stool contamination could result in an estimated 36,383 Salmonella cells passing from telephone receiver to finger to mouth - this is easily enough to result in illness.

Similarly, the researchers calculated that a small amount of nasal secretion deposited onto a kitchen tap could result in 11 viruses being passed from tap to finger to mouth - once again, enough to cause infection.

Previous studies by the same team showed that the common household sponge may contain 320 million disease-causing germs.

Based on a transfer efficiency of 0.0009%, just under 3,000 bacteria could be transferred to the hand and 32 passed from the fingertip to the mouth.

The findings were reported at the 100th General Meeting of the American Society for Microbiology in Los Angeles.

A spokesman for the Society said: "This work shows that everyday activities in a contaminated household or workplace could easily result in the transmission of disease.

"Disease can probably be transmitted in the home more often than these studies suggest because many of these articles are used repeatedly in the home.

"For instance, a homemaker will handle a contaminated kitchen sponge many times during the day, multiplying the probability of disease transmission."

Don't worry

That route of infection is not significant

Professor Tom Humphrey, Public Health Laboratory Service

Professor Tom Humphrey, head of the Public Health Laboratory Service food microbiology research unit, said people should not worry about picking up infection from every possible source in the home.

Professor Humphrey said: "Theoretically it is possible that people could be infected by bacteria and viruses in sponges, taps and phones but that route of infection is not significant."

He said infection with bacteria such as Salmonella was much more likely to come from unhygienic handling of meat products.

In fact, Salmonella infections had dropped by a third during the last two years.