Rocky mountain spotted fever in the United States, 2000-2007: interpreting contemporary increases in incidence.
Rocky Mountain spotted fever (RMSF), a potentially fatal tick-borne infection caused by Rickettsia rickettsii, is considered a notifiable condition in the United States. During 2000 to 2007, the annual reported incidence of RMSF increased from 1.7 to 7 cases per million persons from 2000 to 2007, the highest rate ever recorded. American Indians had a significantly higher incidence than other race groups. Children 5-9 years of age appeared at highest risk for fatal outcome. Enzyme-linked immunosorbent assays became more widely available beginning in 2004 and were used to diagnose 38% of cases during 2005-2007. The proportion of cases classified as confirmed RMSF decreased from 15% in 2000 to 4% in 2007. Concomitantly, case fatality decreased from 2.2% to 0.3%. The decreasing proportion of confirmed cases and cases with fatal outcome suggests that changes in diagnostic and surveillance practices may be influencing the observed increase in reported incidence rates.
Openshaw
John J
JJ
Division of Viral and Rickettsial Diseases, National Center of Zoonotic, Vector-Borne, and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Swerdlow
David L
DL
Krebs
John W
JW
Holman
Robert C
RC
Mandel
Eric
E
Harvey
Alexis
A
Haberling
Dana
D
Massung
Robert F
RF
McQuiston
Jennifer H
JH
D000818:Animals; D002648:Child; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000639:trends; D006801:Humans; D015994:Incidence; D012284:Rickettsia rickettsii; D012373:Rocky Mountain Spotted Fever / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology