In the summer of 2010, two autochthonous dengue fever cases were detected in Croatia. Here we report the retrospective detection of an additional case of dengue fever, representing the first sustained autochthonous transmission in Europe since 1928. In addition, we present the phylogenetic analyses based on two sequences from the Pelješac peninsula, southern Croatia. The sequences were identified as dengue virus genotype 1 and recovered from two out of the three Pelješac patients in whom infection occurred.

In the last few years, several imported cases of Zika virus (ZIKV) infection were reported in European countries. We report the first imported ZIKV infection case in a Croatian traveler returning from Brazil. The patient presented with a low-grade fever, pruritic rash, general weakness, myalgia, arthralgia and edema of the legs and recovered completely within a week. ZIKV infection was confirmed by detection of IgM/IgG antibodies using enzyme-linked immunosorbent assay (ELISA) and confirmed by plaque-reduction neutralization test (PRNT). ZIKV IgM antibodies cross-reacted with dengue virus (DENV), West Nile virus (WNV) and tick-borne encephalitis virus (TBEV) in ELISA. In indirect immunofluorescence assay (IFA), IgM cross-reactivity was found only with DENV-3. ZIKV IgG antibodies cross-reacted with DENV in both ELISA and IFA. PRNT for DENV was negative. Control serology performed on days 64 and 98 after disease onset showed a decline in cross-reactive heterologous DENV IgG antibodies compared to persistently high titer of homologous ZIKV IgG antibodies.

Background/Objectives: Croatia is among the European countries with moderately high antibiotic consumption and correspondingly elevated antimicrobial resistance (AMR) rates. National-level surveillance, however, masks substantial county-level heterogeneity that is relevant for targeted stewardship. This study aimed to (i) quantify and statistically test temporal changes in total antibacterial consumption (J01), beta-lactam antibiotics (J01C), and macrolides/lincosamides/streptogramins (J01F) across all 21 Croatian counties between 2017 and 2024, spanning the pre-pandemic, pandemic, and post-pandemic periods, and (ii) characterize geographic disparities that could inform region-specific stewardship interventions. J01C and J01F were selected because they are, respectively, the most heavily consumed and the most steadily rising antibiotic subgroups in Croatia, and both carry direct relevance to the WHO Access, Watch, Reserve (AWaRe) stewardship framework. Methods: A retrospective, registry-based analysis of antibiotic consumption in all 21 Croatian counties was conducted using annual distribution data from the Croatian Agency for Medicinal Products and Medical Devices (HALMED), covering 1 January 2017 to 31 December 2024. Consumption was expressed as defined daily doses per 1000 inhabitants per day (DDD/TID). County-level values for 2017, 2020, 2021, and 2024 were compared using paired Student’s t-tests (confirmed with Wilcoxon signed-rank tests) and a Friedman test across all four time points; national annual means (2017–2024) were compared descriptively against European Union/European Economic Area (EU/EEA) surveillance benchmarks. Results: National J01 consumption declined from 21.16 to 16.96 DDD/TID between 2017 and 2021 (−19.8%) and rebounded to 22.75 DDD/TID by 2024 (+34.1%); the county-level decline and rebound were both statistically significant (paired t-tests, p < 0.001 for each comparison; Friedman χ² = 57.97, p < 0.001). J01C followed the same U-shaped pattern, temporally coincident with the COVID-19 pandemic period (12.59 → 5.13 → 9.05 DDD/TID; all comparisons p < 0.001), whereas J01F rose continuously throughout the study period, without a corresponding dip during that period (2.81 → 3.49 → 4.43 DDD/TID; p < 0.001 for every interval). Croatia’s 2024 mean county-level J01 consumption was significantly above the 2024 EU/EEA population-weighted mean of 18.8 DDD/TID (one-sample t-test, p = 0.016). The sharpest pandemic-era declines and post-pandemic rebounds were concentrated in Adriatic coastal counties (Primorje-Gorski Kotar, Zadar, Šibenik-Knin, and Istria). Conclusions: Total and beta-lactam antibiotic consumption in Croatia followed a U-shaped trajectory temporally coincident with the COVID-19 pandemic period, while macrolide, lincosamide, and streptogramin use rose steadily throughout 2017–2024, a pattern of stewardship concern given that this subgroup is predominantly classified as “Watch” under the WHO AWaRe framework. Coastal counties displayed disproportionate fluctuations, plausibly reflecting seasonal population dynamics not captured by resident-population denominators. AWaRe-stratified, tourism-adjusted, county-level surveillance is recommended to guide targeted stewardship.