False-Positive Serology for Rocky Mountain Spotted Fever in Long Island, New York, during 2011-2021

Cases of rocky mountain spotted fever (RMSF) are increasingly reported every year in Long Island, New York. In clinical practice, an uncommonly high number of referrals with a positive RMSF IgG test result have been seen in our tick-borne disease clinic. The aim of this study is to describe the clinical-epidemiological characteristics and outcomes of hospitalized patients with positive serologies for RMSF in our academic center in Long Island, NY. We found that out of twenty-four patients with a positive serology for RMSF, only one case met the case definition per CDC criteria, two had suspected RMSF, and the other twenty-one did not have a clinical picture consistent with RMSF. A high number of false-positive RMSF serology may be due to other spotted fever rickettsioses in Long Island. Further studies are needed to investigate the presence of another Rickettsia spp. (such as Rickettsia amblyommatis) in this area that may affect humans.

Automated summary

Cases of RMSF are increasing in Long Island, New York. A high number of referrals with positive RMSF IgG test results have been seen in a tick-borne disease clinic, but most of them do not have a clinical picture consistent with RMSF. False-positive serologies may be due to other spotted fever rickettsioses in the area, and further studies are needed to investigate the presence of other Rickettsia spp. in this area that may affect humans.