Q Fever in the United States: Summary of Case Reports from Two National Surveillance Systems, 2000–2012

Abstract

Abstract. Q fever is a worldwide zoonosis historically associated with exposure to infected livestock. This study summarizes cases of Q fever, a notifiable disease in the United States, reported to the Centers for Disease Control and Prevention through two national surveillance systems with onset during 2000-2012. The overall incidence rate during this time was 0.38 cases per million persons per year. The reported case fatality rate was 2.0%, and the reported hospitalization rate was 62%. Most cases (61%) did not report exposure to cattle, goats, or sheep, suggesting that clinicians should consider Q fever even in the absence of livestock exposure. The prevalence of drinking raw milk among reported cases of Q fever (8.4%) was more than twice the national prevalence for the practice. Passive surveillance systems for Q fever are likely impacted by underreporting and underdiagnosis because of the nonspecific presentation of Q fever.

Q Fever Reporting: Tip of the Iceberg?

“…10 The current report shows that exposure history alone, while a clue to diagnosis, should not preclude clinicians from considering the diagnosis. 1 Only a third of the cases in the current report had exposure. Coupling this with another article suggesting that C. burnetii is more common in the environment than we think should make us broaden our perspective as to when to consider Q fever as a possibility in our differential diagnosis.…”

“…9 Although 60% of cases in the current study were hospitalized, many patients have minimal symptoms. 1 In general, patients who have a mild flu-like illness are unlikely to seek care or are seen on an outpatient basis. They often are treated empirically and diagnostic testing is not conducted unless they fail to improve.…”

“…1 Confirmation requires a clinically compatible illness with laboratory confirmation. Of note, the CDC definition changed slightly between the reporting periods (2000-2007 and 2008-2012).…”

“…Based on statistical modeling, the authors estimated that for every case reported by a CRF there are 13 or more cases that go unreported. 1 The second article examined case fatality through the Multiple Causes of Death (MCD) database (summary of death certificates in the United States) and CRF from 2000 to 2011. There were 33 unique cases (1 case was a match between the systems) of fatal Q fever reported during this period.…”

Coxiella burnetii Infection in a Community Operating a Large-Scale Cow and Goat Dairy, Missouri, 2013

“…Q fever in the absence of reported ruminant exposure is commonly observed in passive surveillance in the United States, with the majority of cases reported from 2000 to 2012 having no known exposure to goats, cows, or sheep. 19 Windborne spread of infected particulates is a recognized mode of exposure implicated in several Q fever outbreaks. [7][8][9]20 Abnormally dry and drought conditions in the region of Missouri where Community A is located during Summer 2013 could have been especially conducive to windborne spread of C. burnetii in dust.…”