Table 2.

Comparison of epidemiological features of human monkeypox by surveillance period and epidemiological setting

Feature	1970–79	1981–86	1996–97	2003
Location	Central and western Africa	Democratic Republic of Congo	Democratic Republic of Congo	Central USA
Epidemiological setting	Passive surveillance	Active surveillance	Outbreak	Outbreak
Number of reported cases	47	338	419*	81
% laboratory confirmed	87	100	Not known	40
Median age (years)	4	Not known	Not known	27
Suspected primary source(s)	Not known	“Forest animals”	Not known	Prairie dog, Gambian giant rat
Primary cases (%)	91	72	22	100
Secondary cases (%)	9	28	78	0
Secondary attack rate (%)	3·3	3·7†	8·0	0
Case-fatality rate (%)	17	10	1·5	0
Previous vaccinia	9%	13%	6%	25%‡
vaccination	(with vaccine scar)		(with vaccine scar)

^*Excludes 92 cases that were identified in an earlier investigation of the same outbreak but not included in the analysis of the subsequent cases.

^†Among household contacts.

^‡Proportion of the confirmed cases for which information was available.