Outbreak of Q fever in Lohra-Rollshausen, Germany, spring 1996

Specific risk factors for contracting Q fever: lessons from the outbreak Jena

A Q fever outbreak with 331 reported cases in seven weeks occurred in a densely populated residential district in Jena (Germany) in 2005. Prompt identification of a stable infection source follow by an intense information policy, well defined and stable meteorological conditions and a large number of reported cases within one small community all allowed us to study promoting and protecting factors of Q fever. We conducted a cross-sectional study and investigated a part of the affected area for 100% sampling (in-home interviews). Out of 608 residents at home 460 (75.7%) participated in the study and 101 fulfilled our definition of an acute Q fever case. Our data revealed a critical zone for residency within 500 m of herds of gestating ewes in a typical urban dwelling area. We found an association between shift work and contracting Q fever. An association between outdoor activity and Q fever was only found after prolonged outdoor stays, on average more than 4h/day. Only open windows facing the putative source were associated with increased risk of Q fever. Therefore fully open windows of more than 6h/day is a significant parameter.

Q fever: single-point source outbreak with high attack rates and massive numbers of undetected infections across an entire region

BACKGROUND

In early 2009, a dairy-goat annex care farm in South Limburg, the Netherlands, reported 220 Coxiella burnetii-related abortions in 450 pregnant goats. These preceded human cases and occurred in a region that was Q-fever free before 2009, providing a unique quasi-experimental setting for investigating regional transmission patterns associated with a Q-fever point source.

METHODS

Index-farm residents/employees, visitors, and their household contacts were traced and screened for C. burnetii. Distribution of community cases was analysed using a geographic information system. True incidence, including undetected infections, was estimated regionwide by seroprevalence in a pre- versus postoutbreak sample, and near-farm by immunoglobulin M seroprevalence in a municipal population sample. Environmental bacterial load was repeatedly measured in surface and aerosol samples.

RESULTS

Serological attack rate was 92% (24/26) in index-farm residents/employees, 56% (28/50) in visitors, and 50% (7/14) in household contacts, and the clinical attack rate (ie, the proportion of persons seropositive for acute infection who also had clinical illness) was ≥ 80%. Notified symptomatic community cases (n = 253) were scattered downwind from the index farm, following a significant exposure-response gradient. Observed incidence ranged from 6.3% (0-1 km) to 0.1% (4-5 km), and remained high beyond. True incidence of infections was estimated at 2.9% regionwide, extrapolating to 8941 infections; estimated near-farm incidence was 12%. Coxiella burnetii load was high on-farm (2009), and lower off-farm (2009-2010).

CONCLUSIONS

Linking a single dairy-goat farm to a human Q-fever cluster, we show widespread transmission, massive numbers of undetected infections, and high attack rates on- and off-farm, even beyond a 5-km high-risk zone. Our investigation may serve as an essential case study for risk assessment in public health and related fields such as bioterrorism response and preparedness.

High seroprevalence of Coxiella burnetii antibodies in veterinarians associated with cattle obstetrics, Bavaria, 2009

Q fever is a zoonosis caused by Coxiella burnetii. Infection can result in severe disease. However, little is known about the risk of infection in veterinarians. In a cross-sectional study among German veterinarians, participants provided sera and completed an exposure questionnaire. We investigated predictors for seropositivity using multivariable logistic regression modelling. The 424 participants' median age was 40 (18-74) years, and 276 (65%) were female. Sera of 162 (38%) were positive for Coxiella burnetii phase II IgG antibodies (by ELISA and IFAT). Predictors for seropositivity were occupational exposure to cattle (aOR 2.83, 95% CI 1.64-4.87), occupational exposure to sheep (2.09, 1.22-3.58), male sex (1.9, 1.15-3.13), and increasing age (30-39 years: 4.91, 2.00-12.04; 40-49 years: 5.32, 2.12-13.33; >50 years: 6.70, 2.60-17.25; compared with <30 years). When investigating occupational exposure to cattle and sheep in detail in a separate model, the seroprevalence increased with increasing numbers of cattle obstetrics procedures performed per month, and with increasing numbers of individual cattle treated per week. The high antibody prevalence implies a high lifetime-risk of Q fever in veterinarians. Cattle veterinarians, especially those frequently performing obstetrics, should be counseled early in their career on the clinical picture of Q fever, and on specific risks.

Coxiella burnetii and milk pasteurization: an early application of the precautionary principle?

Stringency of milk pasteurization has been established on requirements for Coxiella burnetii as being the most heat-resistant organisms of public heath significance. This paper discusses the estimation of the efficiency of pasteurization time/temperature combinations as required in regulations for food safety. Epidemiological studies have been interpreted as C. burnetii being a significant pathogen causing clinical disease through ingestion of milk. The paper examines the evidence and challenges the designation of C. burnetii as a foodborne pathogen. Consequently it questions the need for pasteurization parameters to be established on its heat resistance characteristics.

Seroprevalence of Coxiella burnetii infections among cats in different living environments

The seroprevalence of Coxiella burnetii infection among pet cats in Japan and Korea and stray cats in Japan was investigated by an indirect fluorescent antibody technique and PCR test. Forty-four (14.2%) of 310 pet cats in Japan were seropositive, as were 15 (41.7%) of 36 stray cats in Japan and 10 (8.6%) of 116 pet cats in Korea. The antibody positive rate in stray cats was significantly higher than that in pet cats, but there was no correlation between the rates in Japanese and Korean pet cats. In this study, the prevalence of C. burnetii infection among cats in different living environments was found and it is difficult to deny that stray cats would be one of the important sources of infection for human Q fever.

Developing national epidemiologic capacity to meet the challenges of emerging infections in Germany

In January 1996, the Robert Koch Institute, Germany's national public health institute, began strengthening its epidemiologic capacity to respond to emerging and other infectious diseases. Six integrated strategies were initiated: developing employee training, outbreak investigation, and epidemiologic research programs; strengthening surveillance systems; improving communications to program partners and constituents; and building international collaborations. By December 1999, five employees had completed a 2-year applied epidemiology training program, 186 health department personnel had completed a 2-week training course, 27 outbreak investigations had been completed, eight short-term research projects had been initiated, major surveillance and epidemiologic research efforts for foodborne and nosocomial infections had begun, and 16 scientific manuscripts had been published or were in press. The German experience indicates that, with a concerted effort, considerable progress in building a national applied infectious disease program can be achieved in a short time frame.