Table 2.
Summary estimates of the number of individuals exposed to primary exposure and subsequent low-level residual Bacillus anthracis environmental contamination
| Incident | Nature of primary exposurea | Numbers potentially exposed to primary exposureb | Numbers potentially exposedc to secondary environmental (residual) contamination | Levels of secondary environmental spore contamination | Duration of secondary exposure | Number of cases resulting from any exposure | Estimated total of individuals potentially exposed to primary exposure and secondary contamination |
|---|---|---|---|---|---|---|---|
| Inhalational anthrax (fatal), Scottish Borders, 2006 | Playing B. anthracis-contaminated drum at a drumming workshop | ~74 (attendees at same drumming classes as fatal case) | ~400d (subsequent hall users) | 333–1000 (CFU per 30 ml sample) (widespread contamination) | 5 months (village hall) | 0 | 478 |
| ~4 (in private residences) | 33–66 (CFU per 30 ml sample) (widespread contamination) | Up to 1 year in one residence | |||||
| Inhalational anthrax (fatal), London, 2008 | Drum making and manipulating contaminated animal hides | 1 (drum making colleague) | NA | No environmental contamination (contamination level on drums and hides ~1000 CFU) | Not known | 0 | 1 |
| Gastrointestinal anthrax, New Hampshire, USA, 2009 | Playing a contaminated drum or exposure to contaminated food | 79 (attendees at drumming workshop) | 5 (living or working at event site) | 20–44 (total CFU)e (two drums: 300 and 171 total CFU) |
3½ weeks (community centre) | 0 | 84 |
| Inhalational anthrax, New York City and Pennsylvania, 2006 | Manipulating/shaving contaminated animal hides for drum making | 4 | 4 (same individuals as previous column) | No quantitative sampling reported but widespread contamination | Not known | 0 | 8 |
| Cutaneous anthrax, Connecticut, 2007 | Manipulating/shaving contaminated animal hides for drum making | 0 | 4 (household members; including one anthrax case) | <10f (total CFU) (household, widespread contamination) (Shed workshop samples indicated ‘heavy growth’ by visual inspection) |
Not known | 1 | 4 |
| Estimated total | 158 | 417 | 1 | 575 |
a
Assumed to be most likely source of exposure following investigation.
b
Assuming there was a ‘one-time’ exposure.
c
Estimates based on reported information.
d
Number based upon estimate of hall users over a 5-month period.
e
The limit of detection by culture was 20 CFU per sample.
f
Culture limits of investigations not given.