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West Nile virus (WNV) danas je jedan od najrasprostranjenijih arbovirusa. U posljednja se dva desetljeća WNV infekcije kontinuirano pojavljuju na području Europe u obliku manjih ili većih epidemija i epizootija. U ovom preglednom radu prikazujemo epidemiološke značajke WNV infekcija koje su dokazane na području Hrvatske i Srbije u kontekstu “Jednog zdravlja”. Prikazani rezultati potvrđuju značaj multidisciplinarne i regionalne suradnje u dijagnostici i praćenju ove (re-)emergentne virusne zoonoze.

In accordance with the noticed growing trend in the number of vector-borne disease cases, the extent of public health significance of this problem is also increasing. However, the strengthening of capacities for suppression of these outbreaks is present. With the aim of protecting population from arbovirus infections, there is a need for continuous monitoring and evaluation of risk factors related to vectors and vector borne diseases and human health, for which data is acquired through monitoring programs. In order to address these issues, several activities must be integrated and taken into consideration: vector surveillance, entomological activity, early detection system, preventive measures, counter-epidemic measures and virus detection in vectors, reservoirs or infected animals. There is a legal framework regarding mosquito monitoring on a local, as well as national level. Additionally, at the initiative of the Croatian Institute of Public Health, invasive mosquito species monitoring is being implemented and continuously conducted since 2016.

During the four pandemic waves, a total of 560,504 cases and 10,178 deaths due to COVID-19 were reported in Croatia. The Alpha variant, dominant from March 2021 (>50% of positive samples), was rapidly replaced by Delta variants (>90%) by August 2021. Several seroprevalence studies were conducted in different populations (general population, children/adolescents, professional athletes, healthcare workers, veterinarians) and in immunocompromised patients (hemodialysis patients, liver/kidney transplant recipients). After the first pandemic wave, seroprevalence rates of neutralizing (NT) antibodies were reported to be 0.2–5.5%. Significantly higher seropositivity was detected during/after the second wave, 2.6–18.7%. Two studies conducted in pet animals (February-June 2020/July–December 2020) reported SARS-CoV-2 NT antibodies in 0.76% of cats and 0.31–14.69% of dogs, respectively. SARS-CoV-2 NT antibodies were not detected in wildlife. Environmental samples taken in the households of COVID-19 patients showed high-touch personal objects as most frequently contaminated (17.3%), followed by surfaces in patients’ rooms (14.6%), kitchens (13.3%) and bathrooms (8.3%). SARS-CoV-2 RNA was also detected in 96.8% affluent water samples, while all effluent water samples tested negative. Detection of SARS-CoV-2 in humans, animals and the environment suggests that the ‘One Health’ approach is critical to controlling COVID-19 and future pandemics.

Lymphocytic choriomeningitis virus (LCMV) is a neglected human pathogen associated with aseptic meningitis, severe systemic infections in immunocompromised persons, and congenital anomalies. Data on the prevalence of LCMV infections are scarce. We analyzed the seroprevalence of LCMV in continental Croatian regions. A total of 338 serum samples of professionally exposed (forestry workers, hunters, agriculture workers in contact with rodents) and non-exposed populations (general population, pregnant women) were tested for the presence of LCMV antibodies using indirect immunofluorescence assay. No participants reported recent febrile disease. LCMV IgG antibodies were detected in 23/6.8% of participants: 9.8% exposed persons and 5.1% non-exposed persons (6.1% in the general population and 3.9% in pregnant women). No participants were LCMV IgM positive. Although higher seropositivity was found in males compared to females (8.9% vs. 4.7%), inhabitants of suburban/rural areas compared to inhabitants of urban areas (9.2% vs. 4.6%), and persons who used well as a source of water compared to those who used tap (11.4% vs. 5.6%), these differences did not reach statistical significance. Results of logistic regression showed that the presence of rodents in the house/yard and cleaning rodent nests were associated with an elevated risk for LCMV infection (OR = 2.962, 95% CI = 1.019–8.607).

Several arboviruses have emerged in Croatia in recent years. Tick-borne encephalitis is endemic in continental counties; however, new natural micro-foci have been detected. Two autochthonous dengue cases were reported in 2010. West Nile virus emerged in 2012, followed by emergence of Usutu virus in 2013. Although high seroprevalence rates of Toscana virus have been detected among residents of Croatian littoral, the virus remains neglected, with only a few clinical cases of neuroinvasive infections reported. Lymphocytic choriomeningitis virus is a neglected neuroinvasive rodent-borne virus. So far, there are no reports on human clinical cases; however, the seroprevalence studies indicate the virus presence in the Croatian mainland. Puumala and Dobrava hantaviruses are widely distributing rodent-borne viruses with sporadic and epidemic occurrence. Hepatitis E virus is an emerging food-borne virus in Croatia. After the emergence in 2012, cases were regularly recorded. Seropositivity varies greatly by region and population group. Rotaviruses represent a significant healthcare burden since rotavirus vaccination is not included in the Croatian national immunization program. Additionally, rotaviruses are widely distributed in the Croatian ecosystem. A novel coronavirus, SARS-CoV-2, emerged in February 2020 and spread rapidly throughout the country. This review focuses on emerging and neglected viruses of zoonotic importance detected in Croatia.

West Nile virus (WNV) danas je jedan od najrasprostranjenijih arbovirusa. U posljednja se dva desetljeća WNV infekcije kontinuirano pojavljuju na području Europe u obliku manjih ili većih epidemija i epizootija. U ovom preglednom radu prikazujemo epidemiološke značajke WNV infekcija koje su dokazane na području Hrvatske i Srbije u kontekstu “Jednog zdravlja”. Prikazani rezultati potvrđuju značaj multidisciplinarne i regionalne suradnje u dijagnostici i praćenju ove (re-)emergentne virusne zoonoze., West Nile virus (WNV) is nowadays one of the most widely distributed arboviruses. In the last two decades, small or large WNV epidemics and epizootics are continuously reported in Europe. In this review, we present the epidemiological characteristics of WNV infections detected in Croatia and Serbia within the "One Health" context. Presented results confirm the importance of multidisciplinary and regional collaboration in the diagnosis and surveillance of this (re-)emerging viral zoonosis.

Floods can pose a number of safety and health hazards for flood-affected populations and rescuers and bring risk of injuries, infections, and diseases due to exposure to pathogenic microorganisms and different biological and chemical contaminants. The risk factors and possible health consequences for the rescuers involved in evacuation and rescuing operations during the May 2014 flood crisis in Croatia are shown, as well as measures for the prevention of injuries and illnesses. In cases of extreme floods, divers play a particularly important role in rescuing and first-response activities. Rescuing in contaminated floodwaters means that the used equipment such as diving suits should be disinfected afterwards. The need for securing the implementation of minimal health and safety measures for involved rescuers is paramount. Data regarding injuries and disease occurrences among rescuers are relatively scarce, indicating the need for medical surveillance systems that would monitor and record all injuries and disease occurrences among rescuers in order to ensure sound epidemiological data. The harmful effects of flooding can be reduced by legislation, improvement of flood forecasting, establishing early warning systems, and appropriate planning and education.

Due to the availability of rapid modes of transport, millions of people travel from one part of the world to another each year, thus enabling the viruses to become world travelers as well. Croatia is becoming an increasingly popular tourist destination, but viruses are traveling along with the tourists. Mosquitoes pose a great threat because, due to their complex relation to pathogenic organisms, they can transmit and cause a disease of epidemic proportions. Over 50 types of mosquitoes were recorded in Croatia, and Asian tiger mosquito Aedes albopictus (Skuse, 1894) was recorded on its almost entire territory. Aedes albopictus is currently the one with the larges potential for transmitting of viruses and zoonoses. Risk assessment on Zika and Dengua virus infections was carried out in Croatia. Act on the Protection of the Population against Communicable Diseases (Official Gazette 35/07) along with related ordinances compels the local government units to plan and implement preventive mosquitoes control in order to prevent mosquito-borne diseases. Competent county institutes of public health are obliged to monitor and supervise the implementation of disinsectization measures. During 2016, Asian tiger mosquito was monitored throughout the Republic of Croatia, and the exact area of its spread was determined. The public is continually informed of preventive and personal protection measures. In Institutes for Public Health there is knowledge, but are often not used in practice, and often misses the effectiveness of treatment disinsection. In order to stop the epidemic, all the competent institutions must take an active part in continually educating the population, and in implementing preventive measures of mosquito control.

Hepatitis E (HE) is an emerging public health problem in developed countries worldwide. Nowadays, it is known that the hepatitis E virus (HEV) has zoonotic potential, whereas domestic pigs and wild boars are recognized as the true reservoirs of the disease. Therefore, the aim of our study was to define the seroprevalence and viral persistence of HEV in pigs and wild boars in Croatia. In total, 1424 samples originating from domestic pigs from 14 counties, and 1000 samples of wild boar origin, collected from 16 counties, were tested during 2016 for the presence of HEV antibodies using a commercially available enzyme linked immunosorbent assay (ELISA). All positive samples, as well as samples originating from in-contact domestic pigs and wild boars, were further tested for the presence of HEV RNA using a real time RT-PCR protocol, followed by a nested RT-PCR protocol as a confirmatory test. In 11 of 14 counties, 469 seropositive domestic pigs were found with an overall seroprevalence of 32.94% (95% CI 30.55-35.42), ranging from 8.33% to 60.00%, depending on their geographical origin. Seropositive wild boars were found in six out of 16 counties, showing an overall seroprevalence of 31.10% (95%CI 28.31-34.04%), ranging from 7.70% to 50.60%. The highest seroprevalence was found in the Vukovar-Srijem and Osijek-Baranja Counties (North-East Croatia) where pig breeding dominates and the highest density of wild boars is recorded. While no positive HEV RNA samples were detected in tested domestic pigs, seventeen serologically positive wild boars (11.33%; 95%CI 7.19-17.14) younger than one year of age were found to be HEV RNA positive, indicating chronic infection and possible prolonged virus spread into the environment. The detected viral presence despite the immune response indicates that wild boars have a key role in HEV epidemiology., Hepatitis E (HE) rastući je javnozdravstveni problem razvijenih država svijeta. Danas je poznato da je uzročnik HE virus koji pokazuje zoonotski potencijal, te su domaća i divlja svinja prepoznate kao rezervoari infekcije. Cilj našeg istraživanja bio je utvrditi seroprevalenciju i opstojnost virusa hepatitisa E (HEV) u domaćih i divljih svinja u Republici Hrvatskoj. Stoga su tijekom 2016. godine pretražena 1424 uzorka podrijetlom od domaćih svinja iz 14 županija i 1000 uzoraka podrijetlom od divljih svinja iz 16 županija komercijalnim imunoenzimnim kompletom (ELISA) za dokazivanje specifičnih protutijela za HEV. Pozitivni uzorci, te negativni uzorci koji su sakupljeni od svinja koje su bile u kontaktu sa serološki pozitivnim svinjama, dodatno su bili pretraženi na prisutnost RNK HEV lančanom reakcijom polimerazom u stvarnom vremenu i umreženom lančanom reakcijom koja se koristila kao potvrdni test. U 11 od 14 županija utvrđeno je 469 serološki pozitivnih domaćih svinja, tj. prevalencija je iznosila 32,94 % (95 % CI 30,55-35,42), a kretala se od 8,33 % do 60,00 % ovisno o geografskom podrijetlu svinja. Serološki pozitivne divlje svinje nađene su u šest od 16 županija uz seroprevalenciju od 31,10 % (95 % CI 28,31-34,04 %), a koja je iznosila od 7,70 % do 50,60 %. Najviša seroprevalencija utvrđena je u Vukovarsko-srijemskoj i Osječko-baranjskoj županiji u kojima je svinjogojstvo dominantna grana stočarstva i gdje je visoka gustoća nastanjenih divljih svinja. Dok u serološki pozitivnih domaćih svinja nije utvrđena prisutnost HEV RNK, u 17 (11,33 %; 95 % CI 7,19-17,14) serološki pozitivnih divljih svinja nađena je HEV RNK i to u divljih svinja mlađih od jedne godine starosti što upućuje na moguću kroničnu infekciju i posljedično prolongirano izlučivanje virusa u okoliš. Dokazani HEV u serološki pozitivnih divljih svinja upućuje na moguću ključnu ulogu divljih svinja u HEV epidemiologiji.

Zika virus (ZIKV) izoliran je 1947. godine iz majmuna na području šume Zika u Ugandi. Do 2007. godine virus se održavao u enzootskom ciklusu na području Afrike uz sporadične humane slučajeve. Nakon epidemije 2007. godine na mikronezijskom otoku Yap bilježe se epidemije na pacifi čkim otocima, a 2015. godine virus je unesen u Brazil odakle se proširio Srednjom i Južnom Amerikom. U prirodnom se ciklusu ZIKV održava između majmuna i različitih vrsta komaraca roda Aedes. U urbanom su ciklusu rezervoar ljudi, a vektori komarci Ae. aegypti i Ae. albopictus. Interhumani prijenos moguć je transfuzijom krvi, presatkom organa, spolnim putem te sa zaražene majke na dijete transplacentno/tijekom poroda. U većine zaraženih osoba (~80 %), ZIKV infekcija prolazi asimptomatski. Klinički se infekcija u >95 % oboljelih očituje kao blaga bolest praćena subfebrilnom temperaturom, osipom, mialgijom, artralgijom te konjunktivitisom. Infekcija nastala tijekom trudnoće može rezultirati spontanim pobačajem ili kongenitalnim malformacijama (mikrocefalija). Najčešće opisana neurološka komplikacija je Guillain-Barreov sindrom. Dijagnostika se potvrđuje detekcijom ZIKV RNA ili ZIKV protutijela. Zbog mogućih križnih reakcija s ostalim fl avivirusima, inicijalno reaktivne rezultate testa ELISA potrebno je potvrditi neutralizacijskim testovima. Na području Hrvatske do sada je testirano ukupno 106 povratnika iz endemskih područja, od kojih je u tri potvrđena klinički manifestna ZIKV infekcija., Zika virus (ZIKV) was isolated in 1947 from a febrile rhesus monkey in the Zika forest, Uganda, and subsequently (1948) from Aedes africanus mosquitoes in the same region. First human cases were reported in 1952 in Uganda and Tanzania.until 2007, ZIKV was maintained in enzootic cycle within Africa with only sporadic human cases reported. After the outbreak on the Yap Island (Federated States of Micronesia) in 2007, several outbreaks were reported on the Pacifi c Islands (French Polynesia, New Caledonia, Cook Islands, Easter Island). In 2015, ZIKV was introduced in Brazil with further spreading across Central and South America. Comparing the pre-epidemic Asian and African lineage strains with the epidemic ZIKV strains, several amino acid substitutions were only present in the epidemic strains which could be associated with changes in virulence and the rapid spread of the virus. In a sylvatic cycle, ZIKV is transmitted between monkeys and different mosquito species of the genus Aedes. In an urban cycle, the virus is transmitted between humans through the bite of infected Aedes aegypti and less effi cient, Aedes albopictus mosquitoes. Some other modes of inter-human transmission have been demonstrated, including sexual transmission, blood transfusion/organ transplantation, transplacental and perinatal transmission. Although ZIKV RNA has been detected in breastmilk, transmission through breastfeeding has not been reported. The majority of infections (~80%) are asymptomatic. The main symptoms associated with ZIKV infection include fever, rash, myalgia, arthralgia and conjunctivitis. However, meningitis, encephalitis and myelitis have also been reported. Guillain-Barre syndrome is the most commonly reported neurological complication. ZIKV infection during pregnancy can result in spontaneous abortion or congenital ZIKV syndrome. The congenital abnormalities associated with maternal ZIKV infection include microcephaly, intracerebral calcifi cations, ventriculomegaly and chorioretinal atrophy. Diagnosis of ZIKV includes direct (viral isolation, RT-PCR) and indirect (serology) methods. ZIKV RNA can be detected in blood, urine, saliva, semen and amniotic fl uid. Since cross-reactive antibodies with other fl aviviruses are commonly observed, especially with dengue virus, initially reactive results should be confirmed using neutralization tests. Due to similar clinical symptoms and geographical distribution, dengue and chikungunya should be included in the differential diagnosis of ZIKV infection. Many importations of ZIKV infections have been reported in European countries since 2013. In Croatia, 106 travelers returning from endemic areas were tested so far. Clinically manifest ZIKV infection was serologically confi rmed in three patients.

Hepatitis E (HE) is an emerging public health problem in developed countries worldwide. Nowadays, it is known that the hepatitis E virus (HEV) has zoonotic potential, whereas domestic pigs and wild boars are recognized as the true reservoirs of the disease. Therefore, the aim of our study was to define the seroprevalence and viral persistence of HEV in pigs and wild boars in Croatia. In total, 1424 samples originating from domestic pigs from 14 counties, and 1000 samples of wild boar origin, collected from 16 counties, were tested during 2016 for the presence of HEV antibodies using a commercially available enzyme linked immunosorbent assay (ELISA). All positive samples, as well as samples originating from in-contact domestic pigs and wild boars, were further tested for the presence of HEV RNA using a real time RT -PCR protocol, followed by a nested RT-PCR protocol as a confirmatory test. In 11 of 14 counties, 469 seropositive domestic pigs were found with an overall seroprevalence of 32.94% (95% CI 30.55-35.42), ranging from 8.33% to 60.00%, depending on their geographical origin. Seropositive wild boars were found in six out of 16 counties, showing an overall seroprevalence of 31.10% (95%CI 28.31-34.04%), ranging from 7.70% to 50.60%. The highest seroprevalence was found in the Vukovar-Srijem and Osijek-Baranja Counties (North-East Croatia) where pig breeding dominates and the highest density of wild boars is recorded. While no positive HEV RNA samples were detected in tested domestic pigs, seventeen serologically positive wild boars (11.33% ; 95%CI 7.19-17.14) younger than one year of age were found to be HEV RNA positive, indicating chronic infection and possible prolonged virus spread into the environment. The detected viral presence despite the immune response indicates that wild boars have a key role in HEV epidemiology

Floods can pose a number of safety and health hazards for flood-affected populations and rescuers and bring risk of injuries, infections, and diseases due to exposure to pathogenic microorganisms and different biological and chemical contaminants. The risk factors and possible health consequences for the rescuers involved in evacuation and rescuing operations during the May 2014 flood crisis in Croatia are shown, as well as measures for the prevention of injuries and illnesses. In cases of extreme floods, divers play a particularly important role in rescuing and first-response activities. Rescuing in contaminated floodwaters means that the used equipment such as diving suits should be disinfected afterwards. The need for securing the implementation of minimal health and safety measures for involved rescuers is paramount. Data regarding injuries and disease occurrences among rescuers are relatively scarce, indicating the need for medical surveillance systems that would monitor and record all injuries and disease occurrences among rescuers in order to ensure sound epidemiological data. The harmful effects of flooding can be reduced by legislation, improvement of flood forecasting, establishing early warning systems, and appropriate planning and education.