Eurosurveillance - Volume 17, Issue 3, 19 January 2012

With reference to the Q fever outbreak in the Netherlands in 2009-10, we tested if an evidence-based approach, comparable to the methodology used in clinical medicine, was appropriate for giving public health advice under time constrains. According to the principles of evidence-based methodologies, articles were retrieved from bibliographic databases and categorised by type and size, outcome, strengths and limitations. The risk assessment was conducted in two months and involved six staff members. We retrieved and read 559 abstracts and selected approximately 150 full text articles. The most striking finding was the lack of sound scientific evidence behind standard treatment regimes for Q fever in pregnancy. Difficulties in applying existing evidence rating systems and in expressing uncertainties were identified as problems during the process. By systematically assessing the evidence on several questions about Q fever, we were able to draw new conclusions and specify earlier statements. We found it difficult to grade the mostly observational studies with the known evidence-based grading systems. There is need to develop new methods for grading evidence from different sources in the field of public health. We conclude that an evidence-based approach is feasible for providing a risk assessment within two to three months.

Large outbreaks of Q fever in the Netherlands from 2007 to 2009 were monitored using notification data of acute clinical Q fever. However, the notification system provides no information on infections that remain subclinical or for which no medical attention is sought. The present study was carried out immediately after the peak of the 2009 outbreak to estimate the ratio between Coxiella burnetii infections and Q fever notifications. In 23 postcode areas in the high-incidence area, notification rates were compared with seroconversion rates in blood donors from whom serial samples were available. This resulted in a ratio of one Q fever notification to 12.6 incident infections of C. burnetii. This ratio is time and place specific and is based on a small number of seroconversions, but is the best available factor for estimating the total number of infections. In addition, as subclinical C. burnetii infection may lead to chronic Q fever, the ratio can be used to estimate the expected number of chronic Q fever patients in the coming years and as input for cost-benefit analyses of screening options.

From 2007 to 2009, the Netherlands faced large seasonal outbreaks of Q fever, in which infected dairy goat farms were identified as the primary sources. Veterinary measures including vaccination of goats and sheep and culling of pregnant animals on infected farms seem to have brought the Q fever problem under control. However, the epidemic is expected to result in more cases of chronic Q fever among risk groups in the coming years. In the most affected area, in the south of the country, more than 12% of the population now have antibodies against Coxiella burnetii. Questions remain about the follow-up of acute Q fever patients, screening of groups at risk for chronic Q fever, screening of donors of blood and tissue, and human vaccination. There is a considerable ongoing research effort as well as enhanced veterinary and human surveillance.

In Europe the incidence of human Q fever has dramatically increased over the previous years. Untreated infections with Coxiella burnetii, the causal agent of Q fever, have been associated with both obstetric and maternal complications. The majority of pregnant women with a C. burnetii infection remain asymptomatic, hence screening could be of value to prevent unwanted outcomes in this high-risk group. We applied the updated Wilson and Jungner criteria to review the evidence for routine screening for C. burnetii infection during pregnancy. Since much uncertainty remains about the incidence, clinical consequences, diagnostics and treatment of C. burnetii infection during pregnancy, routine screening for C. burnetii infection during pregnancy should not be recommended. Rigorous studies to assess the effectiveness of C. burnetii screening are warranted.