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Tuesday, 4 December, 2001, 22:50 GMT
'Thousands of letters' may have anthrax
Employees of Biomarine, Inc, in Washington DC
Investigators are being very cautious
Tens of thousands of letters may have picked up trace amounts of anthrax through contact with infected mail, a top United States expert has said.

Dr Jeffrey Koplan, head of the Centers for Disease Control and Prevention (CDC), emphasised that the risk to any one person was extremely low.

But he admitted that cross-contamination could account for two anthrax deaths that have so far resisted explanation.

Dr Koplan's comments came as investigators said the anthrax used in mail attacks in October was virtually identical to a strain developed more than 30 years ago in a US military biological warfare programme.

A worker removes materials from the infected Hart Senate Office Building in Washington
Key Senate buildings remain closed
The quality and high concentration of anthrax in the powder mailed to two US senators, among others, are a strong link with the US military project, which was shut down in 1969.

The powder is much more concentrated than terrorists were once believed to be capable of producing, but experts have revised estimates of terrorist capabilities in recent months.

Even so, the Federal Bureau of Investigation has recently begun to examine the possibility that the deadly powder came from a government laboratory or a federal contractor's.


The BBC science correspondent Richard Black says any theory about the origin of the anthrax should be treated with scepticism.

"After each of the letters was opened, self-professed experts were quick to draw conclusions in print and on the airwaves - conclusions which often contradicted each other, and were found to have little basis in fact," he says.

Ottilie Lundgren, 94, who died of anthrax in November
Lundgren's death is a mystery
No convincing explanation has been offered as to how two women, Kathy Nguyen, 61, and Ottilie Lundgren, 94, came into contact with the spores that killed them.

Of the three other victims, one had spores mailed to his office and two were postal workers who handled infected letters.

But the Nguyen and Lundgren cases have led the CDC's Dr Koplan to speculate that - contrary to earlier belief - spores could be transferred from one unopened envelope to another.

Spreading spores

"There seems to be the potential for not just hundreds and not just thousands but tens of thousands and maybe more letters to be potentially at risk for some level of cross-contamination," he said.

He said that the length of time since the original letters were found in October suggests the risk of new infections is very low.

Investigators hope than an unopened letter to Senator Patrick Leahy will provide clues about the origin of the attacks.

The letter is the only one that was discovered before it was opened.

Investigators have not yet decided how to open the letter without risking contamination.

See also:

30 Nov 01 | Americas
Anthrax letter could yield clues
22 Oct 01 | Health
Warning over anthrax antibiotic
23 Nov 01 | Americas
Anthrax: Charting the US cases
29 Oct 01 | Sci/Tech
Mail sterilisation: The options
30 Oct 01 | Americas
Q&A: The anthrax mystery
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