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Last Updated: Friday, 11 March, 2005, 00:03 GMT
Cabin air low germ risk to flyers
Image of an aeroplane
Infection risk is low onboard
More air passengers have had infections through food poisoning than from the cabin's recycled air, data shows.

A review in the Lancet found the commonest diseases linked to air travel have been spread via contaminated food. Efficient cabin ventilation has prevented many airborne germs, despite a common conception that these are the biggest culprit.

The US authors stressed that no food- or water-borne outbreaks had been reported in the past five years.

Mile high germs

Dr Mark Gendreau and Dr Alexandra Mangili from Lahey Clinic Medical Centre, in the US, searched for literature on infectious diseases related to air travel.

They found a total of 41 in-flight outbreaks of food poisoning resulting in 11 deaths had been documented between 1947 and 1999.

Salmonella was the most commonly reported infection spread by a commercial airline, with 15 recorded outbreaks between 1947 and 1999, affecting nearly 4,000 passengers and killing seven.

The SARS outbreak of 2002 showed how air travel can have an important role in the rapid spread of newly emerging infections
Co-researcher Dr Mark Gendreau

The last reported case was more than five years ago, and the researchers said the lack of cases was probably because of greater use of pre-packaged frozen meals, and improved food handling and inspection.

There are other ways in which infections can be spread on board an aircraft, including contact with germ-ridden surfaces such as toilet door handles.

Most concern has focused on airborne infections spread by coughs and sneezes in the confined cabin space, said Dr Gendreau.

Computer models have been made that focused on the ventilation of the average commercial aircraft, where up to 50% of the cabin air is recirculated.

Air-borne infections

Investigations of in-flight transmission of tuberculosis suggest that to be at risk from infection it was necessary to sit within two rows of a contagious passenger for more than eight hours.

The computer models showed that doubling ventilation rate in the cabin reduced infection risk by half.

Drs Gendreau and Mangili said the ventilation systems used in commercial aircraft seemed to restrict the spread of airborne infections.

They said the perceived risk was probably greater than the actual risk, but added that many cases were probably never reported and there were more things that could still be done to reduce infection risk.

Airlines could provide alcohol-based hand wash for passengers to use after using the toilet and before eating, for example.

We would like the air to be ventilated every three minutes
Mr Farrol Kahn, director of the Aviation Health Institute

Dr Gendreau said: "Another thing to look into is perhaps increasing the ventilation rate in the air cabin, particularly of there is a known disease outbreak in the country that the aircraft is travelling to or from.

"The SARS outbreak of 2002 showed how air travel can have an important role in the rapid spread of newly emerging infections and could potentially even start pandemics."

He also commended the UK government for its action on air travel infections.

The House of Lords Select Committee on Science and Technology looked into and reported on this issue in 2000.

A number of changes have been made since include the right for environmental health officers to make inspections of aircrafts and ships.

The UK Civil Aviation Authority said the Lancet study made a positive contribution to scientific literature concerning the spread of disease by air.

"We look forward to discussing it with relevant health organisations and bodies," said a spokesman.

Mr Farrol Kahn, director of the Aviation Health Institute, said he would like to see more effective air ventilation systems used on all aircrafts.

"They vary in efficiency. Some are 99.9% effective while others are only 50%.

"We would like the air to be ventilated every three minutes, which is what they did before smoking was banned on aircrafts, not every 12 minutes like now."


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