Epidemiology

Coxiella burnetii infection has been reported in most countries, but not in New Zealand or Polynesia.[5] Prevalence of C burnetii is the highest in Africa and Middle East countries.[6]​ The main transmitters of C burnetii in the Republic of Guinea are ticks.[7]​ One systematic review evaluating European studies reported a significantly higher prevalence of Coxiella spp. in ticks in Mediterranean countries.[8]​ In 2019, 1069 cases were reported in the European Union/European Economic Area (EU/EEA), 958 (90%) of which were confirmed.[9]​ The disease is endemic in Australia and strongly associated with the presence of livestock and abattoirs.[5][10]​​​​ In the US, the incidence is high in the Midwest, although California has reported the highest number of total cases.[11] In 2019, 178 acute and 34 chronic Q fever cases were reported in the US.[12] The largest outbreak recorded to date occurred in the Netherlands between 2007 and 2009, with more than 4,000 cases reported.[13][14][15][16][17]​​​​ The outbreak was mainly confined to the south of the country, and dairy goats were implicated as the source. Clusters of cases have been reported in Israel (including a school outbreak) and Taiwan.[18][19][20]C burnetii infection has also been reported in US military personnel returning from Iraq, and less commonly from Afghanistan.[21][22][23]​​​​ In addition, cases have been reported in travellers recently returned from the tropics and Australia.[24][25]​​​​ Cases tend to occur more frequently in spring and early summer.[26]

Populations at risk of infection include farmers, veterinarians, and abattoir workers. Laboratory personnel are also at risk of infection.[27][28]C burnetii infection is the second most common laboratory-reported infection. Outbreaks have been reported that involve 15 or more people in some institutions. The disease has no race predilection, but is more commonly reported in men.[5] In Australia and France, men are 5-fold and 2.5-fold more likely than women to develop the disease, respectively. This may be related to greater occupational exposure in men or may be linked to the protective role of 17-beta-estradiol in women.[5][29]​ The disease is rare in children, and most patients are older than aged 15 years.[30]C burnetii infection is more prevalent in people aged 30 to 70 years.[31][30]​ In the US, adults aged 60 to 64 have the highest age-related risk of Q fever.[12]

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