17 November 2004
Hemorrhagic Smallpox: the first clue to an aerosol attack?
If smallpox were to be released in the form of an aerosol into the air over a city, or at several locations within a city where thousands of person are exposed at the same time, then the first clue could be dozens of persons developing hemorrhagic smallpox. Rapid recognition of these patients’ disease, for which there would be very few alternative explanations, would allow for an immediate Public Health and medical responses that would significantly decrease the severity of the ensuing smallpox epidemic.
A.R. Rao reported his experience with 240 patients with hemorrhagic smallpox from 1959-1963 in his classic paper in the Journal of the Indian Medical Association volume 43, No. 5, September 1, 1964. He made the following key points that are relevant in 2004 to the potential threat of a smallpox aerosol attack:
1. Hemorrhagic smallpox was rare: 240 patients were seen out of the 10, 857 patients with all types of smallpox seen by Dr. Rao in Madras, India. Thus, overall about 2.2% had hemorrhagic smallpox.
2. He found two types of hemorrhagic smallpox, “early” (100 patients) and “late” (140 patients).
3. Notably, the 100 patients with early hemorrhagic smallpox included 44 women who were pregnant.
4. Patients with early hemorrhagic smallpox died very rapidly, on average only 5.95 days after the onset of their typically very severe prodromal symptoms of fever, “severe headache”, “excruciating backache”, hemorrhages into the skin and mucous membranes (often without ever developing the typical smallpox vesicles or pustules due to the rapidly fatal course).
Since hemorrhagic smallpox is rare (1% “early” type and 1.2% “late” type) then if thousands of persons are exposed today by an aerosol of smallpox, then it is likely that at least several dozens or hundreds will develop hemorrhagic smallpox and become very ill, and die, before the majority of patients who will have the more typical non-hemorrhagic form of smallpox.
Daniel R. Lucey, MD, MPH