There is a nightmarish quality to the unfolding story of the mistaken shipment by the Army of live anthrax spores to a long and growing list of more than 50 sites in 18 states, the District of Columbia and three foreign countries.

How such potentially deadly shipments occurred needs careful examination so that the risk to the public and Army employees is not repeated. Unbelievably, the anthrax traveled by public carriers such as FedEx.

Deputy Defense Secretary Robert Work declared last week that there was no known risk to the general public from the samples, which he described as having a low concentration of anthrax that would not sicken “the average healthy individual.”

There have been “no suspected or confirmed cases of anthrax infections” as a result of the shipments, he added.

But it would be a mistake to consider the live anthrax spores harmless.

In just one location that received them, a military base in Korea, 22 people received treatment for possible exposure. “All personnel were provided appropriate medical precautionary measures to include examinations, antibiotics and in some instances, vaccinations,” the statement from the base said.

Investigations are being conducted by the Pentagon and the Centers for Disease Control, which had its own anthrax scare last year in which 80 lab workers were exposed to live anthrax. Meanwhile, other dangerous pathogens were found to have been handled carelessly.

In the latest instance, the number of individuals who might have been exposed to the anthrax spores could total in the thousands. Like the CDC error, the Army’s breaches of protocol in its handling of anthrax raise serious public health issues. They also bring unwelcome memories of the domestic terror attack in 2001 using live anthrax in which five people died and 17 were taken ill. In that case anthrax spores later traced to an Army laboratory in Maryland were mailed to media and political figures. The events exposed the highly volatile and dangerous nature of anthrax. Two postal workers and two other random individuals were among the victims.

Despite a seven-year investigation, the perpetrator was never positively identified, although the FBI asserted that he was likely a researcher at the Army lab who committed suicide before he could be arrested.

As long as the scope of the current anthrax scare remains unclear, public anxiety about the possibility of infection will remain high.

So does the need for more effective controls of this deadly substance.