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In brief – Research news and discovery A GLOBAL killer’s origins may have been traced back to India. Mycobacterium tuberculosis, the bacterium that causes TB, has thrived in south Asia for millennia, but until now no one had studied the diversity of the strains present. To do this, Niyaz Ahmed and his colleagues from the University of Hyderabad, India, analysed 91 samples of TB taken from all over some degree of protection. However, that might be about to change, because the Indian population is far less well adapted to a recent strain of TB known as Beijing strain, found in India only since 2002. This highly infectious strain is threatening to replace the ancestral one, says Ahmed, who presented his results at a conference in Bangkok, Thailand, last month. Coinciding with a surge in HIV cases, this could spell disaster for the 5.7 million Indians infected with the virus. the country, studying the number and type of short, repetitive DNA sequences within three key genes. They discovered that the ancestral strain is widespread, suggesting that India is the ancient reservoir for TB, from which more recent strains evolved and spread to other countries. This may have enabled the immune systems of people living there to adapt to it, providing Trouble ahead in TB’s birthplace? INTESTINAL worms may not be totally bad news. A study of 1600 children in Vietnam suggests that those infected with hookworm are only 60 per cent as likely as uninfected children to be allergic to dust mites (Journal of Allergy and Clinical Immunology, vol 113, p 1305). While this provides support for the idea that allergic diseases have become more common as children are exposed to fewer infections, it also suggests that theories for how this happens may need adjusting. Bacterial and viral infections stimulate a subset of T-cells called Th1, and the idea was that without exposure to infections, the other subset, Th2, predominate – and cause allergies. It may be, however, that the need to fend off parasites led us to evolve a particularly strong Th2 response, which in the absence of worms could cause allergies by attacking foreign material like pollen. The worms turn… WATCH your step after a night on the town: the majority of people who die after falling down the stairs have been hitting the booze. Roman Bux of the Goethe University in Frankfurt, Germany, analysed 43 fatal falls in the city in order to help insurance companies better understand the underlying causes – they will not pay out on life policies where death was self-induced through intoxication. Of the fatalities, 23 people had been drinking heavily and 19 had pre-existing medical conditions such as heart disease. “We have shown a fatal fall down stairs without an underlying severe disease or alcohol influence is a rare phenomenon,” Bux says (Forensic Science International, DOI: 10.1016/j.forsciint.2006.10.010). Tipplers tend to be the topplers MOUNTAINEERS climbing Mount Everest will have to battle with a cloak of ozone that descends over the peak as the day wears on. During expeditions to Everest in the summer of 2001 and 2002, Tong Zhu from Peking University in Beijing, China, and his colleagues measured ozone and carbon monoxide levels at an altitude of 5000 metres. Taking readings every minute for a week they saw a daily ozone cycle, starting at around 40 parts per billion in the early morning and rising to around 80 ppb by midday, remaining high until midnight (Geophysical Research Letters, DOI: 10.1029/2006GL027726). The pattern correlated with the katabatic wind – a cool breeze caused by the chill from glaciers, which rolls down the mountain during the day – and suggests that the ozone is being sucked down from the stratosphere. At its peak the ozone is equivalent to mildly polluted city air and could pose respiratory problems for mountaineers. “They should try to avoid times when the katabatic wind is strong,” says Hajime Akimoto from the Japan Agency for Marine-Earth Science and Technology in Yokohama. It is the first time that this phenomenon has been observed, but it is likely to occur in other cold, mountainous areas with katabatic winds, like Antarctica. IAN COOK/AXIOM www.newscientist.com 6 January 2007 | NewScientist | 15 Peak progress hampered by ozone from katabatic wind
