Role of sex, age, previous valve lesion, and pregnancy in the clinical expression and outcome of Q fever after a large outbreak.
BACKGROUND
Q fever is a zoonosis caused by Coxiella burnetii. After a large outbreak occurred in the Chamonix Valley in the French Alps in 2002, an extensive surveillance was conducted, to describe the variations in the clinical expression of acute Q fever according to host factors, as well as to monitor the risk of evolution of acute Q fever to chronic Q fever in patients at risk.


METHODS
Three groups of patients with risk factors for evolution of acute Q fever to chronic Q fever were considered: 376 pregnant women, 19 immunocompromised patients, and 91 patients with valvular or vascular abnormalities. A group of 578 people without risk factors for evolution of acute Q fever to chronic Q fever was also tested. Diagnosis of Q fever was based on serologic testing by immunofluorescence assay.


RESULTS
Between 30 August 2002 and 31 July 2003, a total of 1946 serum samples obtained from 1064 persons were tested. A total of 101 patients (9.3%) had acute Q fever diagnosed, and 5 patients (0.5%) had chronic Q fever diagnosed. A diagnosis of acute Q fever was established for 11 pregnant women (2.6% of 379 pregnancies), 5 patients with valvular disease (5.5%), and 85 people without risk factors (14.7%) (71 [27.9%] of 254 symptomatic patients and 14 [4.3%] of 324 asymptomatic patients). A new pregnancy in a woman with negative results of serologic tests for Q fever exposes the woman to a new risk for acute Q fever able to evolve to chronic Q fever. The rates of clinical expression were 90.6% in adult men, 75% in adult women, and 33.3% in children, and they were significantly lower (9.1%) in pregnant women. Evolution to chronic Q fever was observed in 5 patients.


CONCLUSIONS
This study emphasizes the importance of active surveillance in postepidemic conditions, especially among patients at risk, as well as the importance of systematic serologic testing during pregnancy.
Tissot-Dupont
Hervé
H
Unité des Rickettsies, Unité Mixte de Recherche 6020, Université de la Méditerranée, Marseille, France.
Vaillant
Véronique
V
Rey
Sylvie
S
Raoult
Didier
D
D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D004196:Disease Outbreaks; D005260:Female; D006349:Heart Valve Diseases; D006801:Humans; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011778:Q Fever / Q000175:diagnosis* / Q000188:drug therapy / Q000453:epidemiology*; D012307:Risk Factors; D012727:Sex Characteristics
D000900:Anti-Bacterial Agents