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

/AXI

OM

www.newscientist.com 6 January 2007 | NewScientist | 15

Peak progress hampered by ozone from katabatic wind

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