New York

Fears of a biological attack have led to strict research controls. Credit: L. M. ALVAREZ/AP

A rebellion is brewing among US scientists who handle pathogens that could be used in biological warfare. The official list of hazardous bacteria, viruses and toxins is so frustrating to some microbiologists that they are trying to rationalize it.

The ‘select agents’ list, drafted by the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, details some 40 microbes and toxins that could threaten public health if they escaped or fell into the wrong hands. Labs that work with them must follow strict security measures. But some researchers are unhappy with the register, pointing out that relatively innocuous pathogens, such as the fungus Coccidioides immitis, are placed under the same tight restrictions as lethal viruses such as smallpox. “The list is very arbitrary,” says microbiologist Arturo Casadevall of the Albert Einstein College of Medicine in New York.

Critics say that the list was drafted in haste after the 2001 anthrax mail attacks, without sufficient consultation with the scientific community. They say it relies too heavily on whether agents have been used as biological weapons in the past, rather than their potential for use in the future.

Now Casadevall and his colleague Liiseanne Pirofski have suggested a way to redo the list by calculating the biological-weapon potential of each microbe (Trends Microbiol. 12, 259–263; 2004). Their formula considers a pathogen's virulence, ability to jump from person to person, incubation period and capacity to remain in the environment. The CDC's list takes similar factors into account, but not in a quantitative fashion.

The new system could be used to partition microbes into categories reflecting different levels of threat. At the moment, “you're either on the list or you're off it”, says Reynolds Salerno of Sandia National Laboratories in Albuquerque, New Mexico. It could also be used to work out whether emerging infectious diseases should be added. The virus responsible for severe acute respiratory syndrome (SARS), for example, which is not on the list, comes out with a weapon potential above that of anthrax and below that of smallpox.

“The formula is a good attempt to bring order to the process,” says Ian Lipkin, an expert on infectious diseases and biodefence at Columbia University in New York.

As yet, there is no agreement on the precise formula that should be used. Salerno is working on his own formula, which factors in how easily a dangerous strain might be obtained by bioterrorists and the simplicity with which it could be converted into a bioweapon.

Many researchers have mixed feelings about seeing their favourite organism labelled a select agent. On the one hand, they fret about strict security requirements that can hamper their research. On the other, such a listing can help bring in cash, as a separate but overlapping list is used by the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland, to allocate biodefence-research funds.

The existence of such similar, overlapping lists further frustrates researchers. The lists are often confused with each other, says Casadevall — he admits that even the published version of his paper managed to mix up two of the lists without the reviewers or the journal noticing.

The CDC should recruit a panel of experts from the scientific community to resolve these issues, says Janet Shoemaker, head of public affairs at the American Society for Microbiology, who has worked closely with the government over the regulation of biological agents.

For the moment, the CDC says that it has no plans to revise its select-agent list. The NIAID says it plans to talk with other government agencies about possibly using a formula to bring at least some of the various lists into line with each other.