James Martin Center for Nonproliferation Studies
Combating the spread of weapons of mass destruction with training & analysis

CNS Occasional Papers: #9

Dr. Peter B. Jahrling
Principal Scientific Advisor
U.S. Army Medical Research Institute of Infectious Disease
1425 Porter Street
Frederick, MD, 21702-5011

Dr. Zelicoff's analysis of the Aralsk smallpox outbreak is extremely valuable in that it provides strong circumstantial corroboration of suspicions that Soviet bioweaponeers conducted open air testing of smallpox virus on Vozrozhdeniye Island in the Aral Sea. This documentation elevates the theoretical concerns about variola virus as an agent of mass destruction to a new level.

Dr. Zelicoff presents a convincing argument that the index case of the outbreak in Aralsk in 1971 could only have become infected while living and working on a research vessel that she never left during the entire potential exposure and incubation period for smallpox disease. The vessel sailed within 15 km of Vozrozhdeniye Island in late July 1971. This timing corresponds closely with a suspected open-air release of smallpox virus on the island. The circumstantial evidence that she was exposed to variola in the form of an aerosol cloud that drifted downwind is compelling.

A former Soviet bioweapons program official has acknowledged that the release of 400 grams of a weaponized smallpox formulation was associated with a civilian outbreak. Dr. Zelicoff's analysis suggests that the index case was the only individual infected by exposure to the aerosol cloud; subsequent cases arose by conventional transmission mechanisms. That she was the only victim among twelve occupants on the ship can be explained by her duties, which required her to be the deck for long periods of time, including nighttime, in contrast to other crewmembers. The protection against aerosol exposure provided by very modest shelter conditions was documented during the Sverdlovsk anthrax incident (another Soviet BW experiment gone awry) in 1979.

Although we don't know whether the 400-gram payload was disseminated from a point source or a line dissemination device, the dilution of virus over a 15 km radius is substantial; yet sufficient infectivity remained to infect the index case. Had the release been over a densely populated area instead of open water, it is conceivable that many hundreds if not thousands of index cases might have occurred simultaneously. This contingency dramatically impacts the projections for the spread of disease and the feasibility of containment strategies based on ring vaccination. Even the most conservative epidemiological models suggest that ring vaccination alone, after an attack of this magnitude, would be totally inadequate to contain the subsequent outbreak. The plausibility of such an attack is increased by Dr. Zelicoff's analysis. Failure to plan for the contingency of smallpox virus being dispersed by aerosol methodology over U.S. communities would be irresponsible. This realization should prompt a reevaluation of the benefit-to-risk equation for mass immunization. Crash development of a less reactogenic vaccine, and effective antiviral drugs to treat individuals who develop smallpox, regardless of immunization status, are also worthy investments.

Considerable controversy has surrounded Dr. Zelicoff's further suggestion that the smallpox virus strain associated with the Aralsk outbreak apparently caused disease in previously immunized adults and hemorrhagic disease in non-immune children. The numbers are too small for definitive statistical analysis, and alternative explanations can be invoked for the apparent vaccine breakthrough infections and the hemorrhagic diathesis, but the concern that this strain was hotter than average should not be dismissed out of hand. We know that the Soviet bioweapons development program attempted to select natural strains of increased virulence and that one of the selection criteria was hemorrhagic diathesis in mice and embryonated eggs. Overwhelming vaccine induced immunity could be explained by sub-standard vaccine quality or administration; conversely, the weaponized strain could have been selected on the basis of vaccine evasion, although the eventual containment of the Aralsk outbreak by use of the vaccine in question argues against this contingency.

Many of the questions pertaining to the weaponized strain could be addressed if reference materials from this outbreak could be located and analyzed. Dr. Nelja Maltseva, who was associated with the Institute of Viral Preparations (IVP) in Moscow in 1971, was involved in the Aralsk outbreak investigation and it is likely that clinical materials from which variola virus was isolated (as documented in the clinical reports) were archived in the IVP collection. Since that reference repository was moved in 1994 to the more secure Vector facility in Koltsovo, Siberia, it would be helpful if our Vector colleagues would scrutinize the records to determine if any of the isolates can be traced back to the Aralsk outbreak. Neither Vector nor its home agency Biopreparat existed in 1971, so no one associated with that program can be held accountable for the misdeeds of the Ministry of Defense (MOD) pre-1972 bioweapons program. But since western scientists still do not have access to the MOD laboratories, which remain a concern since they still carry out secret work, our Vector colleagues remain our best hope for cracking the case. Even if relevant, infectious materials cannot be identified and located, tissues from the victims of the Aralsk outbreak are likely to exist, preserved in formaldehyde and paraffin-embedded blocks. If so, they can be analyzed by modern techniques of immunology and molecular virology to give insight into the nature and phylogeny of the causative virus. A similar approach, used to analyze pathology specimens associated with the Sverdlovsk anthrax outbreak in 1979, yielded information valuable to infectious disease specialists. By analogy, similar cooperation between knowledgeable Russian and western scientists might answer the disturbing questions raised by Dr. Zelicoff's incisive analysis of the documented smallpox outbreak and its association with Vozrozhdeniye Island.

Return to Occasional Paper #9.