In the episode, according to an NBC synopsis, two children whose parents are Foreign Service officers arrive at the emergency room with fevers, are sent home after treatment, and return shortly afterward with pox-like eruptions covering their bodies. Havoc ensues: The hospital is quarantined and police guard the exits while restless patients begin a small riot in an attempt to escape.

Advance word of the episode caused enough concern at the National Association of City and County Health Officials and the Association of State and Territorial Health Officers -- two organizations whose members staff state, county and local health departments nationwide -- for the groups to issue briefing papers to reporters earlier this week.

Among the points stressed: Naturally occurring smallpox was eradicated in 1977; public health authorities are laying plans to counter a deliberate release of smallpox virus; people exposed to the virus can be protected even after the fact by vaccination.

If that seems an overreaction to a fictional scenario, consider this: A survey released last week by the Centers for Disease Control and Prevention found that doctors and the public are poorly informed about smallpox, mistakenly believing that the virus is still circulating and that the vaccine against it, which can have dire side effects, is safe.

At the CDC, which has been inoculating and training smallpox-response teams since last fall, disease experts consulted informally with producers for "E.R." but have not seen the episode's script.

"I answered technical questions regarding smallpox and some other pox diseases and described some of the things we are doing to prepare, but I wasn't asked for approval of any scenarios," said Dr. Lisa Rotz, a member of the bioterrorism preparedness and response program.