• Purpose: There is a consensus on the main role of the wind in the transmission of C. burnetii, the agent of Q fever, between ruminants and from ruminants to humans. However, no study so far has focused on the mechanisms associated with this airborne transmission. The objective of the present study was, using a mechanistic epidemiological approach, to investigate the processes underlying the so-called wind effect and to assess its influence on the incidence risk for C. burnetii infection. This approach was here applied to the transmission process between dairy cattle herds. • Methods: Ninety-five dairy cattle herds located in the Finistère department (western France) were subjected to samplings of bulk tank milk and indoor dust every 4 months over a one-year period, in order to determine their C. burnetii status using PCR tests. A total of 27 incident herd-periods (negativetested on both PCR tests and becoming positive-tested at least once on the subsequent sampling time) and 71 negative herd-periods (negative-tested on both PCR tests over two consecutive sampling time) were retained for analysis. For a given herd, the effect of (i) the cumulated number of bacteria in herds located under the main wind direction (BW), and (ii) the mean wind speed in this area (WI) on its risk of becoming incident was assessed using logistic regression. • Results: Compared to herds in areas with low WI (≤5.5 m/s), the risk was significantly higher (OR = 4.76; CI: [1.42-16.0]) in herds in areas with high WI (>5.5 m/s) and high BW (>20); whereas the risk was not significantly different from unity in other situations. • Conclusions: In agreement with our assumptions, C. burnetii transmission to a free herd occurs only in case (i) the wind itself transporting from infected sources, and (ii) the load of the contaminated particles/aerosols generated, are high enough to act jointly. • Relevance: These results provide decision makers with relevant basis for orienting preventive actions (eg. vaccination) in rural and peri-urbans areas, in order to lower the C. burnetii burden in the environment, and hence to limit both the transmission between ruminant farms and the zoonotic risk, in areas that are particularly at risk