The measles outbreak in Bulgaria, 2009-2011: An epidemiological assessment and lessons learnt.

Measles re-emerged in a nationwide outbreak in Bulgaria from 2009 to 2011 despite reported high vaccination coverage at national level. This followed an eight-year period since the last indigenous cases of measles were detected. The Bulgarian National Centre of Infectious and Parasitic Diseases collated measles surveillance data for 2009-2011. We analysed data for age group, sex, ethnicity, diagnosis confirmation, vaccination, hospitalisation, disease complications, and death and describe the outbreak control measures taken. The outbreak started in April 2009 following an importation of measles virus and affected 24,364 persons, predominantly Roma. Most cases (73%) were among children < 15 years old. Vaccination status was available for 52% (n = 12,630) of cases. Of children 1-14 years old, 22% (n = 1,769) were unvaccinated and 70% (n = 5,518) had received one dose of a measles-containing vaccine. Twenty-four measles-related deaths were reported. The Roma ethnic group was particularly susceptible to measles. The magnitude of the outbreak resulted primarily from the accumulation of susceptible children over time. This outbreak serves as a reminder that both high vaccination coverage and closing of immunity gaps across all sections of the population are crucial to reach the goal of measles elimination.

Insights into epidemiology of human parvovirus B19 and detection of an unusual genotype 2 variant, Bulgaria, 2004 to 2013.

The present study aimed to determine the role of human parvovirus В19 (B19V) as an aetiological agent in measles and rubella negative fever/rash patients from Bulgaria between 2004 and 2013. A total of 1,266 sera from all over the country were tested for B19V IgM antibodies and all positives were further investigated by polymerase chain reaction (PCR). Overall, 280 sera (22%) were B19V IgM positive and 227 of these (81%) were also PCR positive. The highest number of IgM positives was found among five to nine year-old children (27%). Eight infected women gave birth to healthy children; one fetus was aborted with hydrops fetalis. Of the 55 genetic sequences obtained, 54 belonged to genotype 1a and one grouped as a genotype 2 outlier. Phylogenetic analysis of all available genotype 2 sequences covering the 994 nucleotide non-structural protein 1(NS1)/capsid viral protein 1 (VP1) unique region junction, showed that only one other sequence grouped with the outlier strain, forming a clearly distinct and well-supported cluster of genotype 2 (between-group genetic distance: 3.32%). In accordance with B19V nomenclature, this cluster may represent a new subgenotype 2b. The study showed that B19V infections may be falsely identified as rubella or measles in ca 22% of cases, emphasising the need for laboratory confirmation.

Serological and Molecular Biological Studies of Parvovirus B19, Coxsackie B Viruses, and Adenoviruses as Potential Cardiotropic Viruses in Bulgaria.

BACKGROUND: Inflammatory diseases of the heart (myocarditis, pericarditis) are commonly caused by viruses. Among the human cardiotropic viruses, parvovirus B19, Coxsackie B viruses, and adenoviruses play a leading role. AIM: The aim of the present study was to determine the presumptive causative role of parvovirus B19, Coxsackie B viruses, and adenoviruses in the development of myocarditis, pericarditis and dilated cardiomyopathy by demonstrating the presence of specific antiviral antibodies or viral DNA in patients' serum samples. MATERIALS AND METHODS: We tested serum samples collected between 2010 and 2014 from 235 patients with myocarditis (n=108), pericarditis (n=79), myopericarditis (n=19), dilated cardiomyopathy (n=7), and fever of unknown origin accompanied by cardiac complaints (n=22). The mean age of patients with the standard deviation was 33 ± 18 years. Serological and molecular methods (ELISA for specific IgM/IgG antibodies to parvovirus B19 and IgM antibodies to Coxsackie B viruses and adenoviruses, and PCR for detection of parvovirus B19 in serum samples, respectively) were used in the study. RESULTS: Of all tested 235 serum samples, in 60 (25.5%) positive results for at least one of the three tested viruses were detected. Forty out of these 235 serum samples (17%) were Coxsackie B virus IgM positive. They were found in 17% (18/108) of the patients with myocarditis, in 15% (12/79) of those with pericarditis, in 16% (3/19) of those with myopericarditis and in 32% (7/22) in those with fever of unknown origin. The 63 Coxsackie B virus IgM negative patient's serum samples were tested by ELISA for presence of adenovirus IgM antibodies. Such were found in 4 patients with pericarditis and in 2 patients with fever of unknown origin. Every IgM negative sample (n=189) for Coxsackie B and adenovirus was further tested by ELISA for parvovirus B19 IgM/IgG antibodies. B19-IgM antibodies were detected in 14 patients (7.4%). The percentages for B19-IgM antibodies was 8% (7/90), 5% (3/63) and 31% (4/13) in the patients affected with myocarditis, pericarditis, and fever of unknown origin, respectively. Protective B19-IgG antibodies were found in 108 (57%) of the samples. A B19-PCR signal was detected in all the patients who were B19-IgM positive, and in only 1 patient with positive B19-IgG result, the latter presenting with dilated cardiomyopathy. CONCLUSION: The present study shows the involvement of Coxsackie B, parvovirus B19 and adenoviruses in the development of inflammatory diseases of the heart (myocarditis and pericarditis). It is the first ever study in the country that simultaneously analyzes the prevalence of the three major human cardiotropic viruses.

Detection of Human parvovirus B19 (HPVB19) in serum samples from fever-rash ill individuals during the rubella outbreak (2005) in Bulgaria.

The present study aimed to determine the involvement of the parvovirus B19 (HPVB19) as an etiological agent in individuals with fever-rash infections but not infected with rubella during the rubella outbreak (2005) in Bulgaria. A total of 194 serum samples with negative results for measles and rubella-specific IgM antibodies were tested in the National Reference Laboratory. The individuals aged 5-52 years (mean age 17.2 ± 10.15) were divided into four age groups: 5-14; 15-24; 25-34; and 35+ years old. Serological (indirect enzyme immunoassay - EIA) and molecular (extraction and detection of HPVB19-DNA) methods were used. A genotyping assay of the NS1-PCR product was proceeded with the MfeI restriction enzyme. Out of the total number of samples, 95 samples (48.97%) tested positive for HPVB19-IgM and 109 (56.18%) for HPVB19-DNA. The results from the genotyping assay revealed that genotype 1 (prototype B19) was dominant in 106 from 109 samples (97.25%), while genotype 3 (prototype V9) was detected in only 3 (2.75%). Subjects whose sera tested positive for IgM and had a positive PCR result formed a group that was most frequently linked (in 40% of cases) to acute infection. The highest prevalence was established in the group of the school-age children (5-14 years). The combined application of serological and molecular methods confirms the etiological role of HPVB19, and including virus genotyping, confirms the involvement of HPVB19 in the etiological palette of febrile rash diseases and provides a correct differential diagnostic approach.