RICHMOND, March 5 -- A health care worker who became ill after receiving a smallpox vaccination in Virginia's emergency preparedness program was hospitalized today for observation, the state Health Department announced.

Department spokeswoman Trina H. Lee said the unidentified woman developed a low-grade fever and headache Friday, nine days after receiving the voluntary vaccination on Feb. 19.

On Sunday, the health care worker developed a mild rash on her face and chest, Lee said. The state was notified of her condition the next day.

The woman was admitted to an undisclosed Virginia hospital on the recommendation of her private physician, in consultation with state authorities, Lee added.

Citing patient confidentiality, Lee would not release details about the woman, including her home town, age or employer. A senior state official who spoke on condition of anonymity said the woman resides in southwestern Virginia.

Lee said the patient was one of the 161 public health workers and 59 hospital staffers who received the vaccine as part of the state's initial round of vaccinations in the national preparedness effort against terror attacks.

Smallpox, a highly contagious disease, was eradicated worldwide in the late 1970s, but U.S. officials fear that supplies of the virus, which still exist at labs in the United States and former Soviet Union, could fall into the hands of terrorists.

Lee said the U.S. Centers for Disease Control and Prevention had been notified of the Virginia patient's case, adding that further tests were needed to determine conclusively whether the woman's ailments were a direct result of the smallpox vaccination.

"We're too early on to know," Lee said. The vaccination was the first for smallpox that the woman had received and the rash was persisting, Lee said.

A CDC spokesman said federal officials were aware of the Virginia case and were awaiting further test results.

According to the most recent CDC data, 7,354 public health workers and other emergency responders across the country have been vaccinated for smallpox, with two dozen recipients reporting complications associated with the vaccine, none of them life-threatening.

Moderate to severe symptoms include multiple rashes, blisters or bacterial infection of the vaccination site.

Virginia's initial round of smallpox vaccinations began Feb. 5 and is continuing, Lee said. Police, rescue workers and other emergency personnel will receive the vaccine in the second round.