{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,16]],"date-time":"2026-06-16T04:09:07Z","timestamp":1781582947163,"version":"3.54.5"},"reference-count":15,"publisher":"American Society of Tropical Medicine and Hygiene","issue":"2","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2016,2,3]]},"abstract":"<jats:p>Human ehrlichiosis and anaplasmosis are potentially severe illnesses endemic in the United States. Several bacterial agents are known causes of these diseases: <jats:italic>Ehrlichia chaffeensis<\/jats:italic>, <jats:italic>Ehrlichia ewingii<\/jats:italic>, <jats:italic>Ehrlichia muris<\/jats:italic>-like agent, Panola Mountain <jats:italic>Ehrlichia<\/jats:italic> species, and <jats:italic>Anaplasma phagocytophilum<\/jats:italic>. Because more than one agent may be present in one area, cases of human ehrlichiosis and anaplasmosis may be reported as \u201chuman ehrlichiosis\/anaplasmosis undetermined\u201d when the available evidence does not suggest an etiology to the species level. Here, we present a brief summary of these undetermined cases with onset of symptoms from 2008 to 2012 reported to two passive surveillance systems in the United States. The reported incidence rate during this time was 0.52 cases per million person-years. Many cases (24%) had positive polymerase chain reaction results. Enhanced surveillance in an area where several of these etiologic agents are endemic may provide a better understanding of the epidemiology of ehrlichiosis and anaplasmosis in the United States.<\/jats:p>","DOI":"10.4269\/ajtmh.15-0691","type":"journal-article","created":{"date-parts":[[2015,12,1]],"date-time":"2015-12-01T03:48:05Z","timestamp":1448941685000},"page":"299-301","source":"Crossref","is-referenced-by-count":22,"title":["Undetermined Human Ehrlichiosis and Anaplasmosis in the United States, 2008\u20132012: A Catch-All for Passive Surveillance"],"prefix":"10.4269","volume":"94","author":[{"given":"F. Scott","family":"Dahlgren","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kristen Nichols","family":"Heitman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Casey Barton","family":"Behravesh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"2795","reference":[{"key":"ref1","series-title":"Am J Trop Med Hyg","first-page":"52","article-title":"Increasing incidence of ehrlichiosis in the United States: a summary of national surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii infections in the United States, 2008\u20132012","volume":"94","author":"Nichols Heitman","year":"2016"},{"key":"ref2","series-title":"Am J Trop Med Hyg","first-page":"66","article-title":"Human granulocytic anaplasmosis in the United States from 2008 to 2012: a summary of national surveillance 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endemicity","volume":"7","author":"Hamer","year":"2010"},{"key":"ref11","series-title":"Position Statements 2007 ID-03: Revision of the National Surveillance Case Definition for Ehrlichiosis (Ehrlichiosis\/Anaplasmosis)","author":"Council of State and Territorial Epidemiologists","year":"2007"},{"key":"ref12","series-title":"Intercensal Estimates of the Resident Population for Counties and States: April 1, 2000 to July 1, 2010","author":"U.S. Census Bureau, Population Division","year":"2011"},{"key":"ref13","series-title":"Annual Resident Population Estimates, Estimated Components of Resident Population Change, and Rates of the Components of Resident Population Change for States and Counties: April 1, 2010 to July 1, 2013","author":"U.S. Census Bureau, Population Division","year":"2014"},{"key":"ref14","series-title":"J Clin Microbiol","first-page":"3871","article-title":"Identification of a p28 gene in Ehrlichia ewingii: evaluation of gene for use as a target for a species-specific PCR diagnostic assay","volume":"39","author":"Gusa","year":"2001"},{"key":"ref15","series-title":"Am J Trop Med Hyg","first-page":"124","article-title":"Increasing incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000\u20132007","volume":"85","author":"Dahlgren","year":"2011"}],"container-title":["The American Society of Tropical Medicine and 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