Anthrax 'treated to make it deadlier'

The anthrax had been coated to make it stay airborne

The anthrax spores sent in letters to the US Capitol and media outlets had been coated with a chemical additive so sophisticated that only three countries could have produced them, the Washington Post has reported.

The Post, quoting sources close to the ongoing anthrax investigation, said that only the US, Iraq and the former Soviet Union are known to have developed these kind of additives.

Anthrax cases (Source: CDC)

3 deaths (2 in Washington DC, 1 in Florida)

6 cases inhalation anthrax

7 cases skin anthrax

32 exposures

The additives allow the anthrax spores to remain suspended in the air for longer, making them far easier to inhale and consequently far more lethal.

Meanwhile a second NBC employee in New York has been diagnosed with skin anthrax after handling the contaminated letter sent to news anchor Tom Brokaw last month, officials said.

And US investigators say they have found anthrax in a fifth area of the Capitol complex in Washington.

Click here for a map of the contaminated buildings

According to New York Mayor Rudolph Giuliani and federal health officials, the woman at NBC started showing symptoms of skin anthrax on 28 September and began taking antibiotics on 1 October.

"She has been treated for quite some time with antibiotics, including Cipro," Mr Giuliani said, adding that she was expected to make a full recovery.

So far the investigation has failed to trace the source of the anthrax or pinpoint a possible culprit, but identifying the method used to treat the spores may narrow the field.

Different methods

In the United States, spores were subjected to freeze-drying and chemical treatment.

In the former Soviet Union, a different method for freezing and coating was used, while in Iraq the spores were dried in a single-step process in the presence of aluminium-based clay or silica powder.

Anthrax has been discovered at a fifth location at the Capitol

But one government official with direct knowledge of the investigation said that the evidence currently available suggested it was unlikely that the spores were originally produced in the former Soviet Union or Iraq.

Experts say the discovery of the chemical additive suggests a highly sophisticated production facility, possibly a state-sponsored laboratory rather than a university or temporary laboratory.

The US has still failed to make any link between the anthrax attacks and the terror attacks on 11 September.

But President George W Bush has said he "wouldn't put it past" Saudi-born militant Osama bin Laden, the prime suspect in the attacks on Washington and New York.

New location

At the US Senate anthrax has been found in a fifth location, in a goods lift area of the Senate Hart office, police spokesman Dan Nichols said.

The postal service cannot guarantee the safety of the mail

Last week a letter opened in the office of Senate majority leader Tom Daschle - located in the building - was found to be contaminated with anthrax.

The Hart building and all other congressional office buildings have been closed since the evening of 17 October as tests for anthrax are carried out.

But one office building - Russell - was reopened on Wednesday.

Mounting concerns

A Senate media worker who was in the Hart building has been admitted to hospital for possible inhalation anthrax - the most lethal form of the disease.

Concerns have been mounting following confirmation that two postal workers from a Washington facility died of the disease, and news that a female postal worker at a New Jersey office is seriously ill with suspected inhalation anthrax.

The cases have indicated that letters containing anthrax do not have to be opened to cause a serious threat and the US Postmaster General John Potter has warned the public to "handle their mail carefully."

Click here to return