The Pharmaceutical Journal
Vol 274 No 7344 p432
9 April 2005

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Is there a risk of infection during air travel? more
The pleasures of existence: birdsong at morning and starshine at night more
Increasing incidence of obesity could lead to a fall in life expectancy more

Is there a risk of infection during air travel?

Two doctors from medical centres in the US have commented in the 12 March issue of The Lancet on issues regarding the transmission of infections during commercial air travel. Although infrequently reported and difficult to assess accurately, there is a risk of disease transmission that has received heightened attention, in particular in relation to the aircraft passenger cabin.

During flight the passenger cabin is a ventilated and enclosed environment exposing passengers to hypobaric hypoxia, dryness and humidity and close proximity to fellow passengers. Air circulation patterns on standard commercial aircraft are side-to-side, with air entering the cabin from overhead, and escaping near the floor. There is little front-to-back movement. Normal cabin air exchange rates range from 15 to 20 per hour, which is greater than in a typical office building. Filters remove dust, vapours, bacteria and fungi, and since droplets are also trapped, also most viruses.

The four routes for the spread of micro-organisms are contact, inhalation, physical bodies and vectors. The greatest risk for passengers is probably posed by large droplets, because of the high density and close proximity of passengers. The highest risk is in sitting within two rows of a contagious passenger for a flight lasting more than eight hours.

The degree of cabin ventilation also plays a part. Tuberculosis, coronoviral pneumonia (SARS), common cold and influenza and meningococcal infections are commonest among the airborne conditions. The most common faecal or oral transmission is of salmonella and staphylococcus infections transmitted by contaminated food. Cholera has occasionally been encountered. Mosquitoes have carried malaria, dengue fever and yellow fever. Exotic animals have carried disease pathogens. Bioterrorism offers yet another problem.

Good hand hygiene reduces the risk of disease transmission, and masks are rarely indicated except where a passenger is known to carry a problematic infection. In general, perceived risk is greater than real risk.

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The pleasures of existence: birdsong at morning and starshine at night

Birdsong at morning and starshine at night were cited as two of the pleasures of existence by Robert Louis Stevenson. Certainly it would be a miserable world without singing birds, and a dreary prospect was envisaged by John Keats when he wrote: “The sedge is withered from the lake, / And no birds sing.”

Prompted by such a vision, the ecologist Rachel Carson wrote her ‘Silent spring’ in 1962, drawing attention to the massive and increasing threat posed to humans and their contemporaries by toxic chemicals released into the environment. A few decades earlier, Albert Schweitzer, pleading for a reverent attitude to life, made a similar comment: “Man,” he wrote, “has lost the capacity to foresee and forestall. He will end by destroying the earth.” Human selfishness and shortsightedness show no abatement today.

Studies of birdsong show that it is varied and can be elaborate. Song is not always a competitive mating call but may be stimulated by a sense of achievement and wellbeing induced by free flight and good food. An element of leisure enters into the choice, just as it does with human song. Isolation prompts song and it is noteworthy that species such as sparrows, rooks and jackdaws when they congregate in flocks do no sustained singing but rather chatter among themselves. Flocks of starlings babble, whereas solitary birds tend to break into prolonged song, often in imitation of a regular songster of another species. Swallows assembled along telephone wires sometimes sing as a community.

Birds with a rich song rarely display startling coloured plumage. It is the duller species — nightingales, larks, linnets, blackbirds and thrushes — that are the prize songsters. Large birds tend to be songless, possibly because song serves to establish a prestige that small birds may lack but large ones enjoy.

The greatest song variety exists in the evolutionarily more advanced species, where the blackbird and thrush take prime place. Indeed, the blackbird has been called “the Beethoven of birds”. Unfledged birds in the nest can be heard developing their voices and normally, but not invariably, learn from their parents.

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Increasing incidence of obesity could lead to a fall in life expectancy

There is no shortage of reports of the enormous rise in the incidence of obesity these days. And there is also no shortage of warnings that being overweight is a recipe for disaster.

In the New England Journal of Medicine for 17 March a report of research by 10 experts from Chicago and Boston indicates that

by the year 2050 the extension of life expectancy in the US, which has been rising since 1900, could level off or decline, not through a heedless attitude to the environment but through an explosive increase in obesity, especially in childhood. If these fears are true, then future generations may become sicker and die earlier than their parents, for the first time in recorded history.

It is forecast that one in eight children aged six to 19 years will prove to be overweight, with a body mass index of 25 to 30, and, when adult, will rank as obese, with a BMI exceeding 30. The health implications of obesity include an increased incidence of diabetes, which carries complications of heart disease, stroke, loss of limbs, kidney failure and blindness, and also hypertension, asthma, cancer and gastrointestinal disorders. Methods of treating such chronic illnesses are, to be sure, improving with the passing of time, but where access to health care is limited, the negative effect of obesity on life expectancy will continue. Reversal of the effect may take decades, even if it is taken in hand immediately.

Meanwhile, it is a healthy sign that close attention is being paid to the improvement of school meals, discouragement of children from eating junk foods, and their encouragement to indulge in physical exercises. Their elders, regrettably, show a great reluctance to abandon a lazy attitude to daily living. Perhaps the growing attitude to smoking is a hopeful sign, but there are still far too many commercial interests, particularly in the field of ready-made foods, that are impeding progress towards a healthier lifestyle.

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