Nationwide Q Fever Hospitalizations in Italy, 2014-2023: Evidence of Underrecognition and a Sardinian Hotspot.

BACKGROUND

Q fever is a zoonotic disease caused by Coxiella burnetii. In Italy, serologic evidence shows exposure in humans and livestock, but surveillance data are sparse, and underreporting is likely. We aimed to characterize Q fever-related hospitalizations in Italy during 2014-2023 and examine environmental risk correlates.

METHOD: We conducted a nationwide retrospective study using the Italian National Hospital Discharge Database. Hospitalizations with ICD-9-CM code 083.0 as primary or secondary diagnosis were included. We calculated hospitalization rates by age, sex, and region and described clinical characteristics. We linked hospitalizations with climatic, livestock, and land-use data; for Sardinia, we fitted Bayesian spatial regression models including bovine, ovine, and caprine density, temperature, precipitation, and land use.

RESULTS

We identified 428 hospitalizations (67% male), corresponding to a rate of 0.07 per 100 000 person-years. Rates were highest in children and older adults. The overall case fatality ratio was 2.4%. The most frequent Q fever-related concomitant diagnosis was pneumonia. Sardinia had the highest case count and adjusted hospitalization rate, 7-fold the national rate (0.55 vs 0.07). Spatial models for Sardinia showed hotspots in the north of the island and a 12% increase in spatial hospitalization risk per 10 bovine heads/km2 (adjusted relative risk 1.12, 95% credible interval 1.03-1.24).

CONCLUSIONS

Q fever causes an underrecognized burden of hospitalizations in Italy, with marked regional heterogeneity and a Sardinian hotspot associated with high cattle density areas. Clinical awareness, surveillance, and One Health interventions are warranted in high-risk areas.