title: Use of the Historical Limits Method to Detect Increases in Primary and Secondary Syphilis, Arizona 2011-2014: An Exploratory Study.
abstract: Increasing numbers of reported primary and secondary (P&S) syphilis cases in the United States suggest the need for improved surveillance methods. An outbreak detection method using reported syphilis test results, which can be counted before the conclusion of a syphilis case investigation, could lead to timelier outbreak detection.
  
  
  
  The historical limits comparison method was used to compare the number of positive rapid plasma reagin results reported during 2011-2014 with data for the preceding 3 years. An outbreak alert was generated when the monthly count of positive rapid plasma reagin quantitative results was greater than the historical mean plus 2 standard deviations for 2 consecutive months.
  
  
  
  Three outbreak alerts occurred during 2011-2014. The first alert occurred in December 2012 in Maricopa County (Phoenix area). Primary and secondary cases subsequently increased from 10 in January 2013 to 15 in March followed by 5 months of consecutive increases. A second alert was generated for Maricopa County in May 2014. Primary and secondary cases increased from 29 in May to 42 in July 2014. Reported cases remained elevated for approximately 7 months after the second alert. In December 2013, an outbreak alert occurred for Pima County (Tucson area). The number of reported P&S syphilis cases in Pima County increased from 6 in February to 15 in March. Counts of reported cases remained elevated for approximately 6 months after the alert.
  
  
  
  Use of historical limits comparison method based on syphilis laboratory results can provide an outbreak alert before increases in reported cases of P&S syphilis.
authors.affiliation: From the *Arizona Department of Health Services, STD Program; †Maricopa County Department of Public Health, STD Program, Phoenix; ‡Pima County Department of Public Health, STD Program, Tucson, AZ; and §Division of STD Prevention, Centers for Disease Control and Prevention, Atlanta, GA.
authors.forename: Joe Robert
authors.initials: JR
authors.lastname: Mireles
authors.forename: Roxanne
authors.initials: R
authors.lastname: Ereth
authors.forename: Tom
authors.initials: T
authors.lastname: Mickey
authors.forename: Richard
authors.initials: R
authors.lastname: May
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Taylor
mesh_terms: D001130:Arizona / Q000453:epidemiology; D002601:Chancre / Q000453:epidemiology; D004196:Disease Outbreaks; D062665:Epidemiological Monitoring; D006801:Humans; D013587:Syphilis / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control