Based on a recommendation from the Centers for Disease Control, all federal offices, including USPS, are switching from Cipro to doxycycline as precautionary treatment for anthrax exposure.

Doxycycline poses a substantially lower risk of side effects than Cipro when used long term, and is more readily available, the CDC said. USPS switched to the drug yesterday.

Thus far, at least 8,800 employees have been tested for exposure to anthrax, while about 13,300 are on medication. USPS has ordered the environmental testing of 202 mail processing and distribution centers nationwide, including 30 facilities announced Friday. Testing has begun in some facilities, while preparations are being made to test the remainder.

Six facilities have been temporarily closed. Three employees have been hospitalized with confirmed inhalation anthrax. And three employees have been confirmed with cutaneous anthrax.

Early test results from 12 employees of a Topeka, KS, postal repair center are negative for anthrax exposure. Results from the center's other 166 employees are not yet available.

Flags at all postal facilities resumed flying at full staff yesterday. The flags had flown at half-staff since last Thursday in honor of Thomas Morris and Joseph Curseen, who died of inhaled anthrax.