An outbreak of haemorrhagic fever with renal syndrome linked with mountain recreational activities in Zagreb, Croatia, 2017.

In 2017 Zagreb faced the largest outbreak of haemorrhagic fever with renal syndrome (HFRS) to date. We investigated to describe the extent of the outbreak and identify risk factors for infection. We compared laboratory-confirmed cases of Hantavirus infection in Zagreb residents with the onset of illness after 1 January 2017, with individually matched controls from the same household or neighbourhood. We calculated adjusted matched odds ratios (amOR) using conditional logistic regression. During 2017, 104 cases were reported: 11-81 years old (median 37) and 71% (73) male. Compared with 104 controls, cases were more likely to report visiting Mount Medvednica (amOR 60, 95% CI 6-597), visiting a forest (amOR 46, 95% CI 4.7-450) and observing rodents (amOR 20, 95% CI 2.6-159). Seventy per cent of cases (73/104) had visited Mount Medvednica prior to infection. Among participants who had visited Mount Medvednica, cases were more likely to have drunk water from a spring (amOR 22, 95% CI 1.9-265), observed rodents (amOR 17, 95% CI 2-144), picked flowers (amOR 15, 95% CI 1.2-182) or cycled (amOR 14, 95% CI 1.6-135). Our study indicated that recreational activity around Mount Medvednica was associated with HFRS. We recommend enhanced surveillance of the recreational areas during an outbreak.

Influenza vaccine effectiveness estimates in Croatia in 2010-2011: a season with predominant circulation of A(H1N1)pdm09 influenza virus.

This is a retrospective study using the test-negative case-control method to estimate seasonal 2010-2011 influenza vaccine effectiveness (VE) in Croatia. Of patients consulting a physician for influenza-like illness (ILI) and for whom a swab was taken, we compared RT-PCR influenza-positive and RT-PCR influenza-negative patients. We used a structured questionnaire and physicians' records to obtain information on vaccination status and potential confounders. We conducted a complete case analysis using logistic regression to measure adjusted VE overall, against A(H1N1)pdm09 and in age groups. Out of 785 interviewed patients, 495 eligible patients were included in the study, after applying exclusion criteria [217 cases, of which 92·6% were A(H1N1)pdm09 positive, 278 controls]. Crude VE was 31·9% [95% confidence interval (CI) -40·9 to 67·1] and adjusted VE was 20·7% (95% CI -71·4 to 63·3), with higher VE in youngest and oldest age groups. Results from this first VE study in Croatia suggest a low to moderate VE for the 2010-2011 season. Studies year on year are needed with a greater sample size to provide more precise estimates, and also by age group and risk groups for vaccination.

First evidence of simultaneous occurrence of West Nile virus and Usutu virus neuroinvasive disease in humans in Croatia during the 2013 outbreak.

PURPOSE: We report on first evidence of simultaneous occurrence of West Nile virus (WNV) and Usutu virus (USUV) neuroinvasive infection in humans in Croatia during the transmission season 2013. METHODS: From June to December 2013, a total of 95 patients with clinically suspected WNV infection (WNV fever and neuroinvasive disease) were tested for WNV IgM/IgG antibodies using enzyme-linked immunosorbent assay. Twenty-six reactive samples were further tested by virus neutralization test for confirmation. RESULTS: WNV neuroinvasive infection was confirmed in 20 patients, while in three patients USUV neutralizing antibodies were detected. Cases occurred during the 11-week interval (from 24 July to 07 October 2013). Both WNV and USUV cases were distributed in three north-western Croatian counties. In addition to human cases, recent asymptomatic WNV infection (detection of IgM antibodies) was recorded in 9/3,460 (0.3 %) tested sentinel horses. Infected animals were recorded in two eastern and one north-western county. CONCLUSIONS: Our results indicate co-circulation of WNV and USUV in Croatia. WNV infection could be misdiagnosed with other emerging infectious diseases presenting with neurological symptoms such as USUV infection.

Enhanced epidemic intelligence using a web-based screening system during the 2010 FIFA World Cup in South Africa.

The 2010 FIFA World Cup took place in South Africa between 11 June and 11 July 2010. The European Centre for Disease Prevention and Control (ECDC), in collaboration with the hosting authorities, carried out enhanced epidemic intelligence activities from 7 June to 16 July 2010 for timely detection and monitoring of signals of public health events with a potential to pose a risk to participants and visitors. We adapted ECDC's routine epidemic intelligence process to targeted event-based surveillance of official and unofficial online information sources. A set of three specifically adapted alerts in the web-based screening system MedISys were set up: potential public health events in South Africa, those occurring in the participating countries and those in the rest of the world. Results were shared with national and international public health partners through daily bulletins. According to pre-established ECDC criteria for the World Cup, 21 events of potential public health relevance were identified at local and international level. Although none of the events detected were evaluated as posing a serious risk for the World Cup, we consider that the investment in targeted event-based surveillance activities during the tournament was relevant as it facilitated real-time detection and assessment of potential threats. An additional benefit was early communication of relevant information to public health partners.

Spotlight on measles 2010: excretion of vaccine strain measles virus in urine and pharyngeal secretions of a child with vaccine associated febrile rash illness, Croatia, March 2010.

We describe excretion of measles vaccine strain Schwarz in a child who developed a febrile rash illness eight days after primary immunisation against measles, mumps and rubella. Throat swabs and urine specimens were collected on the fifth and sixth day of illness, respectively. Genotyping demonstrated measles vaccine strain Schwarz (genotype A). If measles and rubella were not under enhanced surveillance in Croatia, the case would have been either misreported as rubella or not recognised at all.

A measles outbreak in Croatia, 2008.

We report an outbreak of measles in Croatia, involving 49 cases with onset of symptoms between end of April and June 2008. Cases occurred in Zagreb and Slavonski Brod but investigations indicated a common epidemiological link between these two geographically separate regions.

Enumeration of haemagglutinin-specific CD8+ T cells after influenza vaccination using MHC class I peptide tetramers.

With emergence of MHC class I tetramers loaded with CD8+ T-cell viral epitopes, it is possible to study virus-specific CD8 cells in humans during infection and after vaccination. MHC class I tetramers was used to detect the frequency of haemagglutinin (HA)-specific T cells in 26 healthy influenza-vaccinated humans. Peripheral blood was collected before, and 7, 14 and 28 days after vaccination. Four-colour flow cytometry was used for monitoring of vaccine induced T-cell response. In 15 donors, two- to fivefold increase in frequency of HA-specific T cells was observed 7 days after vaccination. In addition, in 12 of these donors, this increase was accompanied with fourfold increase of H1N1 antibody titre. The increase in frequency of HA-specific CD8+/IFN-gamma+ cells was low and peaked 28 days after vaccination in three of the six donors tested. Frequencies of HA-specific CD8+ T cells and antibody titre returned to prevaccination values 1 year after vaccination. Subunit influenza vaccines have the ability to induce HA-specific CD8+ cells. As the immune response to this vaccine decreased significantly after 1 year, our results confirm the importance of annual immunization for adequate protection.

Transmission of the L-Zagreb mumps vaccine virus, Croatia, 2005-2008.

We report on three cases of symptomatic transmission of the L-Zagreb mumps vaccine virus from three vaccinated children to five adult contacts. The five contact cases were parents of the vaccinated children and presented with parotitis and in one case also with aseptic meningitis. The etiology of the contacts' illness was determined by viral culture, genomic sequencing, serology and epidemiological linking. Two of the vaccinated children developed vaccine associated parotitis as an adverse event three weeks following immunization. Symptoms in contact cases developed five to seven weeks after the vaccination of the children. The five contact cases, as well as the three children with adverse events recovered completely. The children had been vaccinated with MMR vaccine produced by the Institute of Immunology Zagreb, each of them with a different lot. One of the possible explanations for these adverse events is that the very low levels of wild mumps virus circulation in the last decade, combined with waning immunity in those who received one dose of vaccine or suffered from mumps in childhood, resulted in susceptible young adults and that this unique epidemiological situation allows us to detect horizontal transmission of mumps vaccine virus.

Prevalence and dynamics of cytomegalovirus infection among patients undergoing chronic hemodialysis.

Cytomegalovirus (CMV) is an important pathogen in immunocompromised individuals. The aim of this study was to analyze prevalence and dynamics of CMV infection among patients undergoing chronic hemodialysis. From 2010 to 2012, a total of 162 patients and 160 control subjects were tested for the presence of CMV IgM and IgG antibodies using enzyme-linked immunosorbent assay. IgM/IgG reactive samples were further evaluated for IgG avidity to confirm or rule out recent primary CMV infection. The overall IgG seropositivity was higher in hemodialysis patients compared to controls (90.7% vs. 81.9%; crude odds ratio [OR] =2.02, 95% confidence interval [CI] =1.05-3.89; OR adjusted for age and gender = 2.18, 95% CI = 1.05-4.55). CMV IgG antibody titers were similar in both groups. There was no difference in CMV prevalence between males (87.9%) and females (96.3%). According to age, a progressive increase in seropositivity was observed in both hemodialysis patients and the control group. Three hemodialysis patients (1.9%) developed recurrent CMV infection (positive IgM with high avidity IgG antibodies). In one patient (2.9%), seroconversion was documented during the second year of the follow-up period indicating primary infection. In contrast, in the control group, recent primary CMV infection (positive IgM with low/borderline IgG avidity) was demonstrated in three subjects (1.9%), whereas one (0.6%) developed recurrent infection. On multivariate logistic regression, hemodialysis and older age were significant predictors for CMV seropositivity.

Cost-effectiveness of pneumococcal conjugate vaccination in Croatia.

OBJECTIVE: Pneumococcus is a known cause of meningitis, pneumonia, sepsis, and acute otitis media in children and adults globally. Two new vaccines for children have the potential to prevent illness, disability, and death, but these vaccines are expensive. The Croatian Ministry of Health has considered introducing the vaccine in the past, but requires economic evidence to ensure that the limited funds available for health care will be used in the most effective way. METHODOLOGY: Croatia appointed a multidisciplinary team of experts to evaluate the cost-effectiveness of introducing pneumococcal conjugate vaccination (PCV) into the national routine child immunization program. Both 10-valent and 13-valent PCV (PCV10 and PCV13) were compared to a scenario assuming no vaccination. The TRIVAC decision-support model was used to estimate cost-effectiveness over the period 2014-2033. We used national evidence on demographics, pneumococcal disease incidence and mortality, the age distribution of disease in children, health service utilization, vaccine coverage, vaccine timeliness, and serotype coverage. Vaccine effectiveness was based on evidence from the scientific literature. Detailed health care costs were not available from the Croatian Institute for Health Insurance at the time of the analysis so assumptions and World Health Organization (WHO) estimates for Croatia were used. We assumed a three-dose primary vaccination schedule, and an initial price of US$ 30 per dose for PCV10 and US$ 35 per dose for PCV13. We ran univariate sensitivity analyses and multivariate scenario analyses. RESULTS: Either vaccine is estimated to prevent approximately 100 hospital admissions and one death each year in children younger than five in Croatia. Compared to no vaccine, the discounted cost-effectiveness of either vaccine is estimated to be around US$ 69,000-77,000 per disability-adjusted life-years (DALYs) averted over the period 2014-2033 (from the government or societal perspective). Only two alternative scenarios were borderline cost-effective (US$ per DALY averted less than 3×GDP per capita of approximately US$ 40,000). The first was a scenario based primarily on the WHO 2008 pneumococcal disease burden estimates for Croatia. The second was a scenario that assumed a fairly dramatic drop in the price of the vaccine over the period. Both vaccines would need to be priced at approximately US$ 20 per dose or less to be considered cost-effective under base-case assumptions. PCV10 would be more cost-effective than PCV13 with base-case assumptions, but this is sensitive to the price of each vaccine. CONCLUSION: Based on estimated health and economic benefits in children alone, PCV is unlikely to be cost-effective in Croatia. Both vaccines would need to be priced at less than US$ 20 per dose to be considered cost-effective for children. Further analyses should be conducted to estimate the health and economic burden of pneumococcal disease in older age groups, and to assess the influence on cost-effectiveness results when short-term and long-term indirect effects are included for older individuals. While there are important uncertainties around the price and effectiveness of both vaccines, our analysis suggests there is insufficient evidence to warrant a significant difference in the price of the two vaccines.

A comparative study of reactogenicity and immunogenicity of an oral and an inactivated polio vaccine.

Reactogenicity and immunogenicity of the oral live attenuated (OPV) and inactivated polio vaccines (IPV) were studied in primary vaccination of toddlers. Three doses were administered simultaneously with DPT following the usual schedule valid in Croatia. The two groups of children had about 100 children each. Postvaccinal reactions were recorded for three days after each vaccination, and seroconversion was determined one month after the last injection. Although a conclusive analysis of postvaccinal reactions is not possible, since the staff of four different health centers apparently did not observe the same criteria, vaccination with IPV + DPT was not associated with remarkably more adverse events than OPV + DPT. Seroconversion rates attained with OPV ranged between 95.2% and 99.0%. With IPV, the rates were between 96.5% and 100%. Antibody levels for virus types 1, 2, and 3, as measured by GMT (reciprocal value), were 277, 1017, and 222 for OPV, and 465, 526, and 758 for IPV, respectively. IPV appears to be perfectly acceptable as a substitute for OPV for primary vaccination.

Immunity of the Croatian population to poliomyelitis--a serosurvey.

Eight years after the last case of poliomyelitis it was of a special interest to determine the immunity level of the Croatian population to polio and thus to evaluate the possible risk of the revival of this infection. For this purpose, 200 sera samples were collected from individuals of different age and place of residence. Neutralizing antibodies (NT) for all three polioviruses were searched for. Antibody titers of > or = 1:8 were considered positive. Results of the study showed some 75% of the study subjects to have antibodies to polio type 1 and 2, and some 83% to type 3. Only 4% of the sera tested had no NT antibodies to any of the three types. The lowest mean geometric antibody titer (GMT) was for polio type 3 (GMT3 = 19.4; reciprocal value) and somewhat higher for type 1 (GMT1 = 23.5) and type 2 (GMT2 = 22.6). When the antibody titers were related with the age of the subjects, they were found not to decline with age, which was ascribed to periodical boosters with vaccinal strains. It is stressed that, in spite of the eradication of poliomyelitis achieved in Croatia, compulsory vaccination of the children should be continued until its global eradication.

[Tick-borne meningoencephalitis in Gorski Kotar--new findings]. / Krpeljni meningoencefalitis u Gorskom kotaru--nove spoznaje.

Motivated by the occurrence of a case of suspected tick-borne meningoencephalitis (TBE) in a forestry worker of the Delnice Forestry Enterprise, 139 sera samples were collected from his co-workers, for TBE-specific IgG antibody testing. The commercially purchased ELISA and our own indirect immunofluorescence tests were used. Two sera samples were found positive and another six as inconclusive. All of them were sent for confirmation to the Institute of virology, University of Vienna. The two previously positive sera were also ELISA positive in Vienna, the rest being qualified as negative. Accepting that the first case really had TBE and that the two seropositives have experienced infection with the TBE virus, it is inferred that in the wider region of Delnice there is an until now unknown TBE focus, quiescent there for an unknown period of time.

Outcome of influenza vaccination in combat-related post-traumatic stress disorder (PTSD) patients.

Post-traumatic stress disorder (PTSD) is an anxiety disorder that can occur after exposure to extreme traumatic experience such as war trauma, and is accompanied by fear, helplessness or horror. Exposure to trauma can result in immune dysregulation and influence susceptibility to infectious disease as well as vaccine efficacy. The aim of the study was to determine the relation of psychological stress and the immune response to influenza vaccination in combat-related PTSD patients (n = 28). Detection of anti-viral antibody titre was performed by inhibition of haemagglutination assay. Ex vivo tetramer staining of CD8(+) T lymphocytes was used to monitor T cells specific for human leucocyte antigen (HLA)-A*0201-restricted influenza A haemagglutinin antigens before and after vaccination. Twenty patients showed a fourfold antibody titre increase to one or both influenza A viral strains, and 18 of them showed the same response for both influenza B viral strains. Ten of 15 healthy controls showed a fourfold rise in antibody titre to both influenza A viral strains and eight of them showed the same response for both influenza B viral strains. HLA-A*0201(+) PTSD patients (n = 10) showed a significant increase of influenza-specific CD8 T cells after vaccination. Although those PTSD patients had a lower number of influenza-specific CD8(+) T cells before vaccination compared to HLA-A*0201(+) healthy controls (n = 6), there was no difference in influenza A antibody titre between PTSD patients and control subjects before vaccination. The generated humoral and cellular immune response in PTSD patients argues against the hypothesis that combat-related PTSD in war veterans might affect protection following influenza vaccination.

Some epidemiological data on TBE and Lyme borreliosis in Croatia.

TBE in Croatia was first discovered in 1953 but its mandatory reporting, as a distinct nosological entity, was instituted in 1987. Data presented here concern the 1989-1998 decade. During this period a total of 500 cases of TBE was recorded, ranging from 23 (1990) to 87 (1994) per year, with an average of 50 cases annually. There is only one natural focus in the northern part of the country, between the rivers Sava and Drava. Alleged cases of TBE, as occurring out of the focus (Zadar and Pula), have not been certified. The seasonal distribution of TBE cases is typical, most cases occurring from May to July (75%). As for the age distribution of TBE, a substantial rise is seen after the age of 20, only some 3% of cases occurring in children younger than 10 years. The first documented cases of human Lyme borreliosis in Croatia were published in 1986, its official compulsory reporting starting in 1991. Since then 1464 cases were recorded with an annual average of some 150 cases, varying from 93 (1992) up to 335 (1996). The age distribution is somewhat different from TBE, since the age group 0-9 years recruits 20% of all cases. Nevertheless, most of the diseased are of adult age. About 92% of the cases occur between May and August. The disease occurs mostly in the inland, above the 45th parallel, and only sporadically on the Adriatic coast.

Role of epidemiologic information system in sudden death prevention among Croatia's haemodialysis patients.

The main aim of Croatia's epidemiological information system is to enable the monitoring of infectious diseases as well as to enable necessary interventions. Its 24-hour epidemiologic alert mechanism made it possible for initial reports of sudden death clusters in haemodialysis units to reach epidemiologists on the night of 12 October 2001. The alert about the sudden deaths among haemodialysis patients in two hospitals has prompted us to do an epidemiological inquiry during that night and early the next morning. It looked at suspicions of a possible link between Baxter Plivadial P-15 lot 2001F075 dialyser and these deaths. As the suspicion was based on a small amount of data, it needed confirmation from a countrywide inquiry involving the other 40 haemodialysis units. A phone inquiry showed that 23 haemodialysis deaths occurred on 8-13 October 2001. It suggested that also dialyser of a different type and lot (P-18 2001B17R) should be incriminated. During the inquiry (October 13), all haemodialysis units were informed of the suspicions regarding incriminated dialysers, and of the necessity of temporary withdrawal of these from use. The withdrawal on 13 October of incriminated dialysers stopped the deaths among haemodialysis patients. No more such sudden deaths have been recorded since that could be linked either to the described period or to this clinical picture.

Hepatitis A control in a refugee camp by active immunization.

An outbreak of hepatitis A occurred among children of a refugee camp in Croatia. In order to disrupt the outbreak, we decided to vaccinate children from 1 to 15 years of age in the camp, in addition to intensified general preventive measures. Assuming high prevalence of hepatitis A virus antibodies within this population, we conducted anti-HAV testing of the children eligible for vaccination. Of 108 children tested, 74 (68.5%) were anti-HAV positive. We vaccinated 34 children. One month after vaccination 31 previously negative children were tested for anti-HAV and 30 of them were found positive, suggesting a seroconversion rate of 96.8%. One child fell ill 5 days after vaccination, after whom no new cases of hepatitis A occurred. Thus we conclude that active immunization is a successful means of stopping an outbreak of hepatitis A.