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Under Reporting

Emerging Infectious Diseases, March-April 2000
"In North America, Lyme disease and endemic relapsing fever pose the greatest threat to human health and have received the most attention of the borrelial diseases. Approximately 14,000 cases of Lyme disease are reported in the United States each year; however, the actual number of cases may be 10-fold higher (2)."
MMWR January, 2002
"The findings in this report are subject to at least three limitations. First, because LD is reported through passive surveillance, LD is underreported, and the distribution and demographics of reported cases could be biased. Second, LD is underreported in areas where disease is endemic and might be overreported in areas where disease is nonendemic. Third, not all LD patients present with typical manifestations; other conditions might be confused with LD and laboratory testing might be inaccurate."
MMWR April, 2000
"As with a majority of diseases reported through a passive surveillance system, Lyme disease is underreported. Studies in Connecticut and Maryland estimated 7--12 unreported cases for each reported case (20,21). Additionally, the case definition has limitations of sensitivity and specificity."
MMWR May, 2004
"Surveillance for LD is subject to several limitations. Studies from the early 1990s suggested that LD cases were underreported by six to 12-fold in some areas where LD is endemic (2,3); the current degree of underreporting for national data is unknown. In addition, differences in the demographics of reported cases among states with above- and below-average incidence suggest variation in diagnostic and reporting practices among states. Clinicians are reminded that the LD case definition was developed for surveillance purposes and might not be appropriate for clinical management of individual patients (1)."
CDC Website, November 2004
"The overall incidence rate of reported cases in the U.S. is approximately 7 per 100,000 population, but there is considerable underreporting."
The public health impact of Lyme disease in Maryland
(Referenced in CDC publications)
"Results show that LD is underreported by 10- to 12-fold in Maryland,"
Email to LymeInfo Moderator from the CDC, February 2002:
   "Thank you for your correspondence. Regarding... What percentage of Lyme patients who meet the "surveillance criteria" are not reported? What percentage of patients are not accounted for according to the criteria for surveillance? There are several issues here. Anecdotally the CDC has stated that perhaps only as many as one of every ten Lyme cases are reported. There may be many factors that contribute to this situation: Some people may never recognize their symptoms and do not seek medical attention, physicians may not recognize the disease in some persons or may not fulfill all reporting responsibilities, there may be cases not reported due to errors in the state reporting system. Finally, if people do not meet the surveillance criteria per se, but rather present with unidentified cases that do not meet all the criteria the physicians do not report them. Physicians do not report to the state how many people partially meet the criteria, therefore there are not accurate numbers to know how many people are thus described -- i.e. there are no figures on how many others are seen in physician's practice who are NOT reported, nor how many people do not seek medical attention. "

Surveillance, NOT Diagnosis

Lyme Disease 2008 Case Definition
"This surveillance case definition was developed for national reporting of Lyme disease; it is not intended to be used in clinical diagnosis."
Lyme Disease Surveillance Case Definition (revised September 1996)
"This surveillance case definition was developed for national reporting of Lyme disease; it is NOT appropriate for clinical diagnosis."
From the CDC case definition:
"This surveillance case definition was developed for national reporting of Lyme disease; it is not intended to be used in clinical diagnosis."
CDC Case Definitions for Infectious Conditions Under Public Health Surveillance
"The usefulness of public health surveillance data depends on its uniformity, simplicity, and timeliness. The case definitions contained in this report establish uniform criteria for disease reporting and should not be used as the sole criteria for establishing clinical diagnoses, determining the standard of care necessary for a particular patient, setting guidelines for quality assurance, or providing standards for reimbursement. Use of additional clinical, epidemiologic, and laboratory data may enable a physician to diagnose a disease even though the formal surveillance case definition may not be met."
CDC Case Definition- NOT to be used for management of Lyme patients!
Email to LymeInfo Moderator from the CDC, July 1999:
"Per your inquiry, CDC has no specific program dealing with "chronic" Lyme disease. CDC Lyme disease program focuses on the surveillance, epidemiology, prevention and control of Lyme disease, and does not have a treatment protocol or guidelines on management of LD patients."

Also See

39% increase in Lyme cases in 2007 (pdf)
LDA analysis of 2007 CDC reported Lyme cases
January 2004 Testimony of Dr. Paul Mead of the CDC
On testing and more