An analysis of Q fever patients 6 years after an outbreak in Newport, Wales, UK.

Background: A cohort of 211 factory workers was exposed to a point source of Q fever in 2002. A total of 38 cases and 14 controls took part in a follow-up study 6 years after the outbreak. Aim: To compare Q fever serology, the presence of viable Coxiella burnetii, its DNA and fatigue between patients and controls. Design: Laboratory case study. Methods: Q fever serology was by microimmunofluroescence. Viable C. burnetii was detected by VERO cell culture and SCID mice inoculation with patient blood samples. Coxiella burnetii DNA was detected by qPCR (com1 gene) on patients' PBMC and on VERO cultures after 6 weeks incubation. Fatigue was measured by the Chalder Fatigue Scale. Result: At 6 years after the outbreak, 7 of the 38 patients had become seronegative and 4 of the 14 of the controls had become seropositive for Q fever. None of the patient/control peripheral blood mononuclear cells (PBMC) contained viable C. burnetii by VERO cell culture or by SCID mouse inoculation (death or splenomegaly) and none contained C. burnetii DNA by qPCR. Conclusion: Six years after acute Q fever, some patients had become seronegative but none contained viable C. burnetii or its DNA in their PBMC.