51动漫

The anthrax sent to media offices in New York and Florida was the same strain, US health authorities have announced. It was also milled to fine particles 鈥� a process thought to be technically challenging, leading to charges that whoever made it has the backing of a state.

Forty-five people in the US and three in Kenya have so far tested positive to exposure to anthrax. Offices in New York, Washington and Boca Raton, Florida have been hit. On Wednesday, David Fleming, deputy director of the Centers for Disease Control in Atlanta, said laboratory analysis showed strains sent to the American Media office in Florida and to NBC鈥檚 headquarters in New York were the same.

This suggests a single attacker in both incidents. There were also similarities between the letters that carried anthrax to NBC and to Senator Tom Daschle鈥檚 office in Washington on Monday. But information is not yet available on the strain used in that incident.

Although the identity of the Florida/NBC anthrax has not been confirmed, there are reports that it is the virulent 鈥淎mes鈥� strain. In addition to being found naturally in the US, the strain was produced by the US bioweapons programme that ended in 1969.

鈥淪tate sponsorship鈥�

The anthrax powder sent to Daschle was reportedly milled to a fine particle size of between one and two microns (thousandths of a milimeter). The Florida anthrax must also have been finely milled, as it caused two pulmonary infections.

To cause pulmonary anthrax, clumps of inhaled spores must be between one and five microns wide, the optimum size to penetrate the lungs.

Milling dried anthrax cultures to these sizes is considered the most technically challenging step in making anthrax weapons. Michael Powers of the Chemical and Biological Arms Control Institute, a think tank in Washington, says such particle sizes 鈥渋ndicates some sort of state sponsorship鈥�.

But US experiments show such powders are not that difficult to produce. Last year, in an experiment called Project Bacchus, employees of the US Department of Defense succeeded in covertly producing one kilogram of non-pathogenic bacteria similar to anthrax. The bacteria were milled to particle sizes of 1-5 microns with machinery bought on the open market in the US.

Soviet renegades

鈥淧roject Bacchus showed it was possible for terrorists to do that,鈥� Powers told 51动漫, 鈥渂ut they would still need to acquire the know-how somewhere.鈥� Iraqi scientists, or renegades from the former Soviet programme, are possibilities.

鈥淭he small numbers of victims so far doesn鈥檛 fit the usual pattern for groups such as Al Qaida,鈥� says Powers. That suggests they didn鈥檛 succeed in making enough anthrax for a big attack, he thinks. 鈥淏ut they might keep sending out small quantities like this for some time.鈥�

Richard Spertzel, former head of biological weapons inspection for UNSCOM, the UN body that attempted to dismantle the Iraqi arsenal, told journalists this week that such small quantities were 鈥渨ithin the capabilities of any dedicated individual that鈥檚 determined to do it.鈥�