Boosting aircraft ventilation may cut disease

日期:2019-03-03 06:09:08 作者:迟轩 阅读:

By Andy Coghlan Airlines should boost cabin ventilation onboard aeroplanes in regions with disease outbreaks to prevent transmission of diseases such as tuberculosis or potentially avian influenza, suggests a new study. A fresh review of how airborne disease spreads among air passengers found people sitting as far as seven rows away from a sick passenger risk catching their bug. The previously assumed safe distance of at least two rows away might not be enough to avoid infection during an eight hour flight, depending on the disease, it says. The previous estimate of the two-row safety margin came from studies on the spread of tuberculosis onboard aircraft. But the review says that the wisdom of this was challenged in March 2003 when a single passenger with severe acute respiratory syndrome (SARS) infected 22 fellow passengers on a flight from Hong Kong to Beijing. “This was just a three hour flight, and some infected passengers were seven rows from the one passenger that had the disease,” says Mark Gendreau of the Lahey Clinic Medical Center in Burlington, Massachusetts, US. Despite this apparent threat, Gendreau and co-author Alexandra Mangili of the Tufts-New England Medical Center in Boston, US, conclude that passengers are generally well protected against infection by ventilation systems which operate on most commercial aircraft. On average, these replace cabin air completely every three minutes, usually recycling about half the original air during the flight. When working successfully, these systems clear 63% of airborne bugs with each cycle, especially if they have filters, although these are not mandatory. But in light of the onboard SARS transmissions, airlines should consider increasing ventilation rates in outbreak areas, urges Gendreau. Studies of ventilation showed that doubling the circulation rate halves the risk of infection, he says. This strategy could be useful if there are outbreaks of avian influenza and it turns out to be transmissible between people, says Gendreau, whose review included at least two flu flight outbreaks – one made worse by breakdown of the ventilation system. “Ventilation is very important to prevent spread,” he says, adding that there have been no reports of flu outbreaks onboard aircraft since 1999. Passengers can also protect themselves against by washing hands regularly, or turning their personal blowers to deflect air away from where they are sitting. Ron Behrens, a consultant in tropical and travel medicine at the London School of Hygiene and Tropical Medicine, UK, thinks that the risk of infection is much higher in the departure lounge than in the air. “That’s where you get mixing of the world for a reasonable amount of time in air that’s not exchanged,” he says. “Travellers have very high levels of flu.” Behrens agrees with Gendreau that increased ventilation would help to protect passengers during outbreaks, but doubts whether airlines would oblige, because it uses more fuel. “With cost pressures already as high as they are, if it adds £20 to the cost of a ticket, they’ll say no,” Behrens told New Scientist. It is too early to consider such detailed recommendations from the study, says a spokesman for Britain’s Civil Aviation Authority. “We look forward to discussing it with relevant health organisations and bodies,” he says. Journal reference: The Lancet (vol 365, p 989) More on these topics: