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Bacillus anthracis is a well-known zoonotic pathogen that can cause disease in both animals and humans. Moreover, it has a high bioterrorism potential as its lethal spores are resistant to inactivation, are easy to produce in large quantities, and are easily spread over large areas. Anthrax cases occur in different parts of the world, including most European countries. Specific areas of Croatia are long known as anthrax districts, but with sporadically reported cases over the years. Here, we present a major outbreak of animal and human anthrax in the region of Lonjsko Polje in Croatia, a region not known to have anthrax cases in the past. The outbreak started in July 2022 and lasted several months, but most human and animal cases were reported in the first month. During the outbreak, there were 17 reported human cases of cutaneous anthrax and 29 laboratory-confirmed animal cases. However, due to issues in reporting in animals and the late finding of the carcasses, which made laboratory diagnostics challenging, the actual number of animal cases was probably significantly higher. [ABSTRACT FROM AUTHOR]

Background: Due to rapid spread, the Omicron variant has become the dominant SARS-CoV-2 variant responsible for infections worldwide. We present the first detection of the Omicron variant in Croatia which resulted in rapid cross-border spreading. Methods: Whole-genome sequencing was performed using the Illumina MiniSeq sequencing system. SARS-CoV-2 lineages were identified using the PANGOLIN and GISAID databases. Results: The first case of the Omicron variant (BA.1.17) emerged in Croatia after a workshop held in Zagreb in November 2021. The patient reported a history of previous COVID-19 and received two doses of an mRNA vaccine. Three additional cases were detected among Croatian participants of the workshop. At the beginning of December, SARS-CoV-2 infection was confirmed in one participant from Montenegro and her husband. Phylogenetic analysis showed that the detected Omicron variants were closely related to the first Croatian case, confirming the connection with the workshop outbreak and rapid cross-border spreading. Subsequent analyses of SARS-CoV-2 positive samples in Croatia showed the rapid introduction of the Omicron variant and depletion of the Delta variant resulting in the fifth pandemic wave. Conclusions: Genomic monitoring and early detection of novel SARS-CoV-2 variants are essential to implement timely epidemiological interventions and reduce further transmission in the population. [ABSTRACT FROM AUTHOR]

Copyright of Croatian Journal of Infection / Infektoloski Glasnik is the property of Croatian Society for Infectious Diseases and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Croatian Journal of Infection / Infektoloski Glasnik is the property of Croatian Society for Infectious Diseases and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Introduction: The data on the coronavirus disease (COVID-19) in solid-organ transplant recipients (SOTRs) in Croatia is unknown. The aim of this study was to analyze the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Croatian SOTRs. Materials and methods: From 7 September to 27 November 2020 (beginning of the second COVID-19 pandemic wave), a cross-sectional screening for COVID-19 was performed in the adult outpatient liver (LTRs; N = 280) and kidney transplant recipients (KTRs; N = 232). Serum samples were initially tested for SARS-CoV-2 IgG antibodies using a commercial enzyme-linked immunosorbent assay (ELISA; Vircell Microbiologists, Granada, Spain). All positive samples were confirmed using a virus neutralization test (VNT). Data on risk exposure and COVID-19 related symptoms were collected using a questionnaire. Results: The transplanted cohort's seroprevalence detected by ELISA and VNT was 20.1% and 3.1%, respectively. Neutralizing (NT) antibodies developed in 15.6% of anti-SARS-CoV-2 ELISA IgG positive SOTRs. The difference in seropositivity rates between LTRs and KTRs was not statistically significant (ELISA 21.1% vs. 19.0%, P = 0.554; VNT 3.6% vs. 2.6%, P = 0.082). Overall VNT positivity rates were higher in patients who reported participation in large community events (5.9% vs. 1.0%; P = 0.027) as well as in patients who reported COVID-19 related symptoms in the past six months. In addition, symptomatic VNT positive patients showed significantly higher (P = 0.031) NT antibody titers (median 128, interquartile range (IQR) = 32-128) compared to asymptomatic patients (median 16, IQR = 16-48). Conclusions: This study showed that 15.6% of anti-SARS-CoV-2 ELISA positive Croatian SOTRs developed NT antibodies indicating protective immunity. Further studies are needed to determine the dynamic of NT antibodies and COVID-19 immunity duration in immunocompromised populations such as LTRs and KTRs. [ABSTRACT FROM AUTHOR]

In 2012 the active WNV surveillance system in horses was introduced in Croatia. Between June and October 2012, in six Croatian counties, 1804 horse sera were sampled and tested for IgM WNV antibodies as the confirmation of an acute infection. Additional 1472 samples were tested for the presence of IgG WNV antibodies in the seroprevalence study. The study showed the increased seroprevalence of WNV infection in horses and acute infections in horses in three Eastern Croatian counties. In the same transmission season, the first human WNV clinical cases were reported in the counties with a confirmed increase in WNV seroprevalence in horses. Even more, the first detection of horses acutely infected with WNV had been two weeks before the first confirmed human clinical case. The results confirmed the active serosurveillance system in horses as a valuable tool for WNV surveillance in Croatia and as the source of important veterinary medicine and public health data. [ABSTRACT FROM AUTHOR]

Neuroinvasive flaviviruses such as tick-borne encephalitis virus (TBEV) and West Nile virus (WNV) are widely distributed in continental Croatian regions. We analyzed clinical characteristics, laboratory parameters, and molecular epidemiology of neuroinvasive flavivirus infections in eastern Croatia. A total of 43 patients with confirmed flavivirus infection hospitalized from 2017 to 2023 were included in the study. Reverse-transcription polymerase chain reaction (RT-qPCR) was used to detect flavivirus RNA in clinical samples (cerebrospinal fluid; CSF, urine). ELISA was used for IgM and IgG antibody detection in serum and CSF with confirmation of cross-reactive samples by virus neutralization test. WNV was detected more frequently (74.4%) than TBEV (25.6%). A statistically significant age difference was found between WNV patients (median 65 years) and TBEV patients (median 36 years). Comorbidities were more frequently detected in WNV patients (hypertension 56.3 vs. 18.2%; diabetes 31.3 vs. 0%). Meningitis was the most common clinical presentation in both TBE and WNV neuroinvasive disease (WNND; 63.6 and 59.4%, respectively). In addition, some rare clinical presentations of WNND were also detected (cerebellitis, polyradiculoneuritis). No significant differences in the frequency of clinical symptoms were observed between WNV and TBEV-infected patients (fever 93.7 vs. 100%; malaise 78.1 vs. 100%; headache 75.0 vs. 100%; nausea 50.0 vs. 63.6%; vomiting 34.4 vs. 54.6%). Comparative analysis of total and differential leukocyte blood count showed similar results. However, CSF pleocytosis was higher in TBE patients, with a significant difference in the neutrophil and lymphocyte count (WNND median 48.5% and 51.5%; TBE median 10.0 and 90.0%, respectively). The length of hospital stay was 12 days for WNND and 9 days for TBE. Phylogenetic analysis of detected WNV strains revealed the presence of WNV lineage 2 in eastern Croatia.

Aim: To assess the humoral immunity to COVID-19 in nursing home residents six months after vaccination., Methods: This seroepidemiological research enrolled 118 residents of one nursing home in Zagreb. All participants received two doses of BioNTech/Pfizer COVID-19 and had no previously detected SARS-CoV-2 infection. The samples were tested for the presence of neutralizing antibodies using a virus neutralization test. A SARS-CoV-2 strain isolated in Vero E6 cells from a Croatian COVID-19 patient was used as a stock virus. Neutralizing antibody titer was defined as the reciprocal of the highest serum dilution that showed at least 50% neutralization. Neutralizing antibody titer ≥8 was considered positive., Results: Sixty-four (54%) participants had a positive neutralizing antibody titer, 27 (23%) had a low positive titer (titer 8), and 27 (23%) had a negative titer. Women had a significantly higher median titer than men (16 [interquartile range, IQR 24] vs 8 [IQR 12], Mann-Whitney U=1033, P=0.003). Age was negatively but not significantly correlated with neutralizing antibody titer (Spearman's rho -0.132, P=0.155)., Conclusion: Almost half of the participants (46%) had a negative or low positive titer six months after having been fully vaccinated. This study suggests that humoral immunity among nursing home residents considerably wanes six months after BioNTech/Pfizer COVID-19 vaccination. Our results could contribute to the discussion about the need for a booster dose.

HIV and sexually-transmitted diseases (STDs) represent a significant public health problem worldwide. We analyzed the seroprevalence and risk factors for HIV, hepatitis B and syphilis in populations with high-risk behaviors in Croatia. During a three-year period, a total of 443 men who have sex with men (MSM) / bisexual persons, sex workers (SW) / clients of SW, persons with multiple sexual partners, and persons with a history of STD were tested for the presence of HIV, hepatitis B virus (HBV), and Treponema pallidum (syphilis) antibodies within the framework of second generation HIV surveillance. Participants were recruited from 11 Croatian counties, the vast majority among clients of voluntary counselling and testing centers. The overall prevalence of HIV, HBsAg, anti-HBc, and syphilis was 1.4%, 2.6%, 12.1%, and 3.4%, respectively. HBV and syphilis seroprevalence differed significantly between, genders with higher prevalence among men (anti-HBc 13.8% vs. 5.7%, P=0.043; syphilis 4.4% vs. 0%; P=0.049), as well as between age groups, with a steady increase according to age. Participants with a history of STD were more often seropositive than participants who did not report STD (HBsAg 8.2% vs. 1.0%, P=0.002; anti-HBc 32.4% vs. 6.4%, P<0.001; syphilis 12.0% vs. 1.7%, P<0.001). Syphilis seroprevalence was higher in homo / bisexual persons (12.2%) compared with heterosexual persons (1.2%, P<0.001). Logistic regression showed that history of STD was a significant risk factor for hepatitis B (HBsAg AOR=6.229, 95% CI=1.491-26.022; anti-HBc AOR=5.872, 95% CI=2.899-11.896) and syphilis seropositivity (AOR=5.572, 95% CI=1.751-17.726), while homo / bisexual behavior was associated with syphilis seropositivity (AOR=12.820, 95% CI=3.688-44.557). Our results highlight the importance of continuing STDs screening and prevention in at-risk populations.

Background: The Epstein-Barr virus (EBV) is one of the most common viruses found in humans, causing lifelong infection in up to 95% of the world population., Objectives: To analyze the seroprevalence of EBV infection in different population groups in Croatia., Methods: During a 2 year period (2015-2016), a total of 2022 consecutive serum samples collected from Croatian residents were tested for the presence of EBV-specific viral capsid antigen (VCA) immunoglobulin M (IgM) and IgG antibodies using an enzyme-linked immunoassay. IgM/IgG-positive samples were further tested for IgG avidity., Results: The overall prevalence of EBV IgG antibodies was 91.4%. Females had significantly higher IgG seroprevalence than males (93.1% vs. 89.9%, P = 0.008). According to age, IgG seropositivity increased progressively from 59.6% in children age < 9 years to 98.3% in 30-39 year olds, and remained stable thereafter (P < 0.001). The IgG seroprevalence differed significantly among groups: 68.1% in children/adolescents and 95.9% in adults; multiple sclerosis (100%), hemodialysis patients (97.7%), heart transplant recipients (93.8%), hematological malignancies (91.2%), and Crohn's disease (88.5%), P < 0.001. IgM antibodies were detected in 9% of participants. Using IgG avidity, recent primary EBV infection was documented in 83.8% of IgM-positive subjects < 9 years old, 69.2% age 10-19, 33.3% age 20-29, and 3.6-4.2% > 40. All IgM positive participants > 40 years showed high IgG avidity. Logistic regression showed that age is associated with EBV IgG seropositivity., Conclusions: EBV is widespread in the Croatian population. Older age appears to be the main risk factor for EBV seropositivity.

Herpes group viruses (herpes simplex virus, HSV; varicella-zoster virus, VZV; cytomegalovirus, CMV; and Epstein-Barr virus, EBV) remain an important cause of morbidity in immunocompromised persons. The aim of the study was to analyze the prevalence of HSV-1, HSV-2, VZV, CMV and EBV in patients undergoing hemodialysis. During a three-year period (2013-2015), 152 consecutive serum samples from hemodialysis patients and 150 healthy subjects (control group) were tested for the presence of IgM/IgG antibodies to herpes group viruses. Serologic tests were performed using a commercial enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunofluorescent assay (ELFA). Hemodialysis patients showed significantly higher CMV IgG seropositivity compared to controls (88.2% vs. 78.7%, p=0.011). In addition, seroprevalence rates of HSV-1 and VZV were higher in hemodialysis patients; however, these differences did not reach statistical significance (85.5% vs. 80.0%, p=0.054 and 99.3% vs. 96.0%, p=0.051, respectively). The prevalence of HSV-2 and EBV was similar in both groups (12.5% vs. 12.7%, p=0.137 and 98.0% vs. 95.3%, p=0.113, respectively). There was no difference in IgG seropositivity according to gender and place of residence. Logistic regression showed that older age was a significant predictor for CMV and EBV IgG seropositivity (increase in age by one year: CMV OR=1.055; 95%CI=1.030-1.080 and EBV OR=1.075, 95%CI=1.023-1.130).

During July 2009 an outbreak in neonates represented with gastrointestinal and respiratory symptoms was observed at the Neonatal Postintensive Care Unit, Clinical Hospital Center, Zagreb. Human parechovirus type 1 (HPeV1) was isolated from seven patients, one of whom was asymptomatic. All but one were premature neonates with serious underlying conditions, and all recovered fully after several days. In order to characterize the HPeV1s, sequencing of the VP1/2A region was conducted on six isolates from the outbreak and four isolates detected in Croatia in 2008 and 2007. The analysis of sequence similarity showed that the nucleotide identity between the prototype strain (Harris) and HPeV1 isolated in Croatia was 76.5-77.5%. Croatian strains from 2007 and 2009 clustered together with strains from the Netherlands and Germany detected in 2003 and 2006, respectively, while strains from 2008 clustered with the strain from Finland detected in 2000. Change of the dominant strains each year may suggest antigenic variation as a result of viral response to specific immunity of the target population., (© 2010 Wiley-Liss, Inc.)