Fig 1.
Flow of case evaluation for inclusion in this analysis.
Case reports retrieved from 1980 to 2019 include all those reported as Rocky Mountain spotted fever (RMSF). Conservative case inclusion criteria were applied as described in methods to focus on those cases most likely to be RMSF. Included in the analysis were 31 confirmed cases and 47 probable cases.
Fig 2.
Confirmed and probable cases of RMSF in California and percent of reported cases confirmed in two 20-year time blocks, 1980 to 1999 and 2000 to 2019.
Table 1.
Demographics, hospitalization, and fatality of reported RMSF cases in California in two 20-year reporting blocks, 1980 to 1999 and 2000 to 2019.
Asterisks indicate where there are statistically differences in proportions with a Z test, p < 0.05 considered significant.
Table 2.
Incidence of RMSF cases per million persons by ethnicity, using ethnicity-specific population estimates, 1980–2019.
The Incidence rate ratio compares the ethnicity specific incidence between 2000–2019 (numerator) and 1980–1999 (denominator) and is a measure of excess risk between the two reporting blocks.
Fig 3.
Number of RMSF cases (both confirmed and probable) by month of onset, 1980 to 2019, stratified by 20-year reporting blocks.
Fig 4.
County of residence of RMSF cases, in 20-year reporting blocks, 1980–2019.
Counties included in the southern region are heavily outlined. Source for base-layer map: File:California counties outline map.svg—Wikimedia Commons (https://commons.wikimedia.org/wiki/File:California_counties_outline_map.svg#filelinks).
Fig 5.
Number and percentage of California RMSF cases where regions of exposure prior to onset could be determined in 20-year reporting blocks, 1980–2019.
Exposure regions are “Northern CA” (California counties north of San Luis Obispo, Kern and San Bernardino Counties; see Fig 4), “Southern CA” (counties not in Northern CA), “US” (any state outside California in the United States) and “Unknown” (travel not specified).
Table 3.
Case outcomes, signs, and symptoms from electronically reported RMSF cases, 2011–2019.
There was no statistical difference in proportions between confirmed and probable cases for case outcomes, signs and symptoms (Z statistic for proportions, p >0.05.).