WASHINGTON (AP) - Even a single case of smallpox would be an international emergency, triggering vaccinations for dozens of people close to the patient in an urgent attempt to contain the highly contagious disease, says a federal plan obtained by The Associated Press.

Detectives would immediately begin retracing the victim's every move over the preceding weeks.

Although many experts consider a bioterror attack with smallpox unlikely, they have long called for better preparedness. Thus, the new plan provides step-by-step instructions for state health workers who would have to battle a disease not seen for decades.

The Centers for Disease Control and Prevention is putting final touches on the plan, work that was accelerated after the Sept. 11 terrorist attacks in New York and Washington. But officials say they consider the plan operational, and have begun sending it to state health departments so they can designate a person in charge of following the rules to make preparations.

The news comes even as some government officials raise the possibility of one day resuming routine vaccinations of Americans against smallpox, inoculations that ended in this country in 1972.

The government has 15.4 million doses of smallpox vaccine and hopes to buy an additional 300 million. "It is the intention to determine, after we have sufficient supplies available to commence inoculation, to make the decision at that time," Homeland Security Director Tom Ridge said Thursday.

Yet chilling photographs in the CDC document show children with severe, sometimes fatal, vaccine side effects - illustrating why routine inoculations would be tough to renew unless smallpox ever reappears.

"You're always hesitant to immunize people against the disease unless you're fairly certain that there is going to be a risk," said Surgeon General David Satcher.

In fact, the plan makes clear that entire cities or states won't get vaccinated unless CDC has evidence of more than a few cases. Instead, the CDC will carefully apportion vaccine to family, friends, co-workers and other close contacts of a smallpox patient, as well as health workers and others who come in contact with a patient in a hospital.

It takes fairly close proximity to catch smallpox - you must be within about six feet of a person suffering the characteristic rash to breathe in the virus - and quickly vaccinating those who live with or work around a patient is protective.

But, "a single case of smallpox would require an immediate and coordinated public health and medical response to contain the outbreak and prevent further infection," warns the plan's opening page.

Smallpox hasn't occurred in the United States since 1949; the world's last naturally occurring case was in Africa in 1977. When smallpox was declared eradicated in 1980, all research stocks of the virus were supposed to be contained at the CDC's Atlanta laboratory and a similar lab in Russia. But the Soviets instead produced smallpox for their bioweapons program in the 1980s, and bioterrorism experts fear some may have spread to terrorist-sponsoring countries.

Smallpox symptoms include fever and a pock-like rash all over the body, appearing between seven and 17 days after exposure to the virus. People are contagious from the time the rash appears - particularly in that first week of illness - until the scabs fall off.

The CDC's emergency plan would kick in when a doctor alerts state or federal health officials that a patient should be tested for smallpox, a test that can be confirmed only at CDC or Fort Detrick, Md.

If someone has smallpox, he or she would immediately be quarantined and CDC Director Jeffrey Koplan would send vaccine from the government's stockpile while alerting the FBI and White House.

Disease detectives would grill the sick person and his family about every step taken for three weeks before becoming ill: Where did you travel? What's your route to work? Who did you have lunch with? Did you go to the movies? They'll also want addresses and phone numbers of every person who had close contact with the patient.

CDC then will have state health officials track down all of those people, vaccinate those who need it, and do daily monitoring of whether they get a fever - a sign they, too, might be sick with smallpox and must be quarantined.

The plan instructs how to give the hard-to-handle vaccine. It is made with a live version of a virus related to smallpox, and thus can cause serious reactions in certain people, including the immune-compromised or people with the skin condition eczema. The document pictures a child covered in eczema-like lesions after contact with a recently vaccinated sibling. The worst reaction is a very rare - one in 300,000 vaccinated babies - but deadly encephalitis.

Copyright 2001 The Associated Press. All rights reserved.