An analysis of historical smallpox outbreaks suggests that the disease is less contagious than many public health planners fear and is an improbable tool for terrorists, a Scottish university researcher concluded in a recent paper (see GSN, Oct. 28).
Writing in October’s Bulletin of the World Health Organization, Aberdeen University biologist Hugh Pennington said smallpox is less contagious than other diseases — including measles, chickenpox, mumps and rubella — and can be quickly contained with standard isolation and ring-vaccination strategies.
Pennington concurred with a 1972 assessment by another researcher that “under contemporary conditions smallpox cannot be said to live up to its reputation. Far from being a quick-footed menace, it has appeared as a plodding nuisance with more bark than bite.”
Pennington found that previous smallpox outbreaks lasted “weeks rather than months or years, that their size was in single figures or tens rather than hundreds or thousands, and that more than three-quarters of the outbreaks ended with the generation being infected immediately after the detection of smallpox.” There is little evidence that smallpox patients can transmit their illness “further than a few meters,” Pennington said.
In addition, while producing the smallpox virus would not be difficult, Pennington said, manufacturing anthrax would be much easier for terrorists because anthrax is much less dependent on precise environmental conditions.
“None of these factors favor smallpox as a weapon of mass destruction,” Pennington said (Hugh Pennington, Bulletin of the World Health Organization, October 2003).