Downward Revision
The number of people living with HIV/AIDS globally has dramatically dropped—not because of an actual drop in the HIV burden but because of better counting methods in India. The Joint United Nations Program on HIV/AIDS (UNAIDS) and the World Health Organization announced last November that the disease’s prevalence in India is 2.5 million—down by more than half from a previous estimate of 5.7 million. A commentary in the December 1, 2007, Lancet explains that previous official counts extrapolated data from large public hospitals. The revised figure derives from a national health survey of 102,000 adults and corroborates earlier findings from a smaller study. The lower estimate means that India will not need to devote as many resources to fight HIV and will not see the same infection rates as sub-Saharan Africa. The numbers support the current prevention strategy of targeting high-risk groups such as sex workers.

Flu in the Cold
Influenza spreads most readily in winter, but crowding and closed windows have nothing to do with that seasonality. Rather cold air and low relative humidity seem to do the trick. Researchers found that infected guinea pigs kept at five degrees Celsius shed the bug for 40 hours longer than those kept near room temperature. The virus was most stable at relative humidities of 20 to 40 percent: dry air leads to smaller water droplets on which viruses are carried, enabling them to remain airborne for long periods. In the cold, cilia in the respiratory system work more slowly, enabling the virus to spread in the respiratory tract and to disperse in a sneeze or a cough.

Fractured Fractals
In authenticating artwork by Jackson Pollock, investigators have used a technique that is intended to extract certain geo­metric patterns thought to permeate the drip painter’s signature splashes. The technique is based on fractals, repeating patterns of varying scales, as seen in the so-called Julia set, shown at the right. In 2006 physicists at Case Western Reserve University challenged the veracity of the method, arguing that the fractals that are supposedly unique to Pollock’s work were also detected in amateur pieces. In an as yet unpublished paper, they contin­ue their attack, showing that some genuine Pollocks failed the test, whereas amateur paintings intended to imitate Pollock’s technique passed.

Richard P. Taylor, a University of Oregon physicist who originally designed the fractal analysis, claims the Case Wes­t­ern team has misapplied his technique, which, he says, should be used with other authentication methods, such as materials analysis. Tay­lor has examined six of a recently discovered cache of 32 suspected Pollock works, of which none so far has reached his mathematical criteria.