Table 1.

The IR, HR, and CFR of reported cases of spotted fever group rickettsiosis by status of Amblyomma americanum within a county and decade of onset of symptoms

	IR*	HR (%)	CFR (%)
Amblyomma americanum within county
Absent	2.28	48.6	1.68
Reported	6.07	33.2	0.74
Established	10.3	27.8	0.65
Decade of onset of symptoms
1980s	–	72.0	2.80
1990s	1.68	51.0	2.03
2000s	5.38	24.4	0.43
2010s	10.0	27.3	0.47

CFR = case fatality rate; HR = hospitalization rate; IR = incidence rate.

The IRs were calculated using case counts from the Nationally Notifiable Disease Surveillance System and population estimates from the United States Census Bureau, Population Division, for 1993–2013. The HRs and CFRs were calculated using the case report form data for 1981–2013. The statistics in this table are crude statistics, not adjusted statistics from our regression models.

^*Cases per million persons per year.