Quantitative estimation of an individual's risk of infection due to airborne pathogens requires knowledge of the pathogen's infectious dose, in addition to estimates of the pathogen's airborne concentration and the person's exposure duration. Based on our review of the published literature on Q fever, we conclude that the infectious dose of Coxiella burnetii is likely one rickettsia, and that the probability of a single organism initiating infection is approximately 0.9. Findings in experiments exposing guinea pigs to C. burnetii via intraperitoneal injection and inhalation of respirable aerosols firmly support a "one-hit" Poisson model of infection. Findings in experiments exposing human subjects to C. burnetii via inhalation of respirable aerosols fail to provide convincing evidence that the one-hit Poisson model applies to human infection; however, inference from the human studies is limited by the small numbers of subjects and lack of quantification of the exposure concentrations. Given the presence of C. burnetii in sputum, the prevalence of cough in Q fever patients, and the ability of the pathogen to initiate infection via the respiratory tract, we believe that person-to-person transmission of C. burnetii via inhalation of respiratory aerosol is possible.
We take your privacy seriously. You can review and change the way we collect information below.
These cookies allow us to count visits and traffic sources so we can measure and improve the performance of our site. They help us to know which pages are the most and least popular and see how visitors move around the site. All information these cookies collect is aggregated and therefore anonymous. If you do not allow these cookies we will not know when you have visited our site, and will not be able to monitor its performance.
Cookies used to make website functionality more relevant to you. These cookies perform functions like remembering presentation options or choices and, in some cases, delivery of web content that based on self-identified area of interests.
Cookies used to track the effectiveness of CDC public health campaigns through clickthrough data.
Cookies used to enable you to share pages and content that you find interesting on CDC.gov through third party social networking and other websites. These cookies may also be used for advertising purposes by these third parties.