US anthrax scare spreads

Investigators are trying to link the different cases

America's anthrax alert has spread to a third state after a letter sent to an address in Nevada tested positive for exposure to the disease.

The letter, which was sent from Malaysia to an office of software giant Microsoft, will now be sent to the Center for Disease Control and Prevention (CDC) for further tests.

Strains of anthrax

Respiratory: Similar beginnings to flu but shock occurs between two and six days later - frequently fatal

Intestinal: Severe food poisoning type symptoms - up to 50% mortality

Cutaneous: Rarely painful skin lesion - fatal in one in 20 cases

Six people are believed to have come into contact with the letter, but health officials believed there is a "low risk" of exposure to the bacteria.

Elsewhere, the CDC has strongly denied reports that five more employees of a Florida newspaper company had been shown to have been exposed to the disease.

The company, American Media Inc, was the site of the first outbreak where three anthrax cases - one fatal - were discovered.

The CDC said tests on American Media Inc employees were not yet conclusive and would take another few days to complete.

A letter sent to broadcaster NBC carried the anthrax spores in a brown granular substance

The latest developments follow confirmation that a letter sent to the New York offices of the American television network NBC contained traces of anthrax.

That letter - sent from Trenton, New Jersey on 18 September and containing a brown granular substance - is believed to have infected an assistant of NBC news anchor Tom Brokaw.

She is now receiving treatment for skin anthrax and is said to be responding well to treatment with antibiotics.

A second NBC employee is reported to be ill with anthrax-like symptoms.

Negative tests

Another letter sent to the same office on 25 September from Saint Petersburg, Florida, and containing a white powdery substance, was initially believed to have contained anthrax, but has since tested negative.

Earlier, the New York Times announced that white powder found in an envelope sent to one of its Middle East reporters also tested negative for anthrax. That letter was postmarked Saint Petersburg too, as was a letter containing a similar substance sent to the Saint Petersburg Times.

Pharmacies are rationing sales of some antibiotics

Hospital emergency centres in parts of the US are reported to be busy with people worried about the scare. Some pharmacies are limiting supplies of ciprofloxacin, an antibiotic used to treat the disease, after unusually strong demand.

President George W Bush, responding to the heightened sense of alert, has called on Americans to not be afraid.

"I understand that many Americans are feeling uneasy, but all Americans should be assured we are taking strong precautions," he said in his weekly radio address.

The FBI has so far ruled out any terrorist link to the cases, although Vice President Dick Cheney has said he cannot rule out the involvement of Osama Bin Laden, who is suspected of masterminding the 11 September terror attacks on New York and Washington.

Experts believe the anthrax so far discovered is not the specially-made type of the disease which would be used in a biological warfare attack.