Lyme disease overdiagnosis in a large healthcare system: a population-based, retrospective study.

OBJECTIVES: To evaluate the impact of false-positive IgM immunoblots on Lyme disease treatment and case reporting in a large healthcare system. METHODS: We obtained the results of all Lyme disease serological tests ordered at U.S. Air Force healthcare facilities in the USA between January 2013 and December 2017. We conducted chart reviews to adjudicate positive IgM immunoblots (from two-tier and independent testing) as true positives or false positives using established criteria, and we assessed whether these cases were reported to the U.S. Department of Defense surveillance system. RESULTS: Of the 18 410 serum tests (17 058 immunoassays and 1352 immunoblots) performed on 15 928 unique individuals, 249/1352 (18.4%) IgM immunoblots were positive. After excluding repeat tests, insufficiently documented cases, and participants with a history of Lyme disease, 212 positive IgM immunoblot cases were assessed. A total of 113/212 (53.3%) were determined to be false positives. Antibiotics were prescribed for Lyme disease for 97/99 (98.0%) participants with a true-positive test and 91/113 (80.5%) participants with a false-positive test. The number of false-positive cases reported to the surveillance system was identical to the number of unreported true-positive cases (n = 44). CONCLUSIONS: Lyme disease serological tests were overused in a large healthcare system, and positive results were frequently misinterpreted, leading to misdiagnosis and widespread antibiotic misuse. Underreporting of true-positive cases was offset by overreporting of false-positive cases, suggesting that the discrepancy between the reported incidence and true incidence of Lyme disease may not be as significant as previously assumed.

Flea market finds and global exports: Four multistate outbreaks of human Salmonella infections linked to small turtles, United States-2015.

Zoonotic transmission of Salmonella infections causes an estimated 11% of salmonellosis annually in the United States. This report describes the epidemiologic, traceback and laboratory investigations conducted in the United States as part of four multistate outbreaks of Salmonella infections linked to small turtles. Salmonella isolates indistinguishable from the outbreak strains were isolated from a total of 143 ill people in the United States, pet turtles, and pond water samples collected from turtle farm A, as well as ill people from Chile and Luxembourg. Almost half (45%) of infections occurred in children aged <5 years, underscoring the importance of the Centers for Disease Control and Prevention recommendation to keep pet turtles and other reptiles out of homes and childcare settings with young children. Although only 43% of the ill people who reported turtle exposure provided purchase information, most small turtles were purchased from flea markets or street vendors, which made it difficult to locate the vendor, trace the turtles to a farm of origin, provide education and enforce the United States federal ban on the sale and distribution of small turtles. These outbreaks highlight the importance of improving public awareness and education about the risk of Salmonella from small turtles not only in the United States but also worldwide.