The Balkan Peninsula and Bulgaria in particular, is a well-known endemic region for Crimean-Congo hemorrhagic fever (CCHF). This study describes the prevalence of Crimean-Congo hemorrhagic fever virus (CCHFV) among tick populations from areas, previously recognized with emerging cases of CCHF disease in humans. These include regions from the Southeastern (regions of Kardzhali and Haskovo) and Central (region of Stara Zagora) parts of the country. For the period 2006-2010 a total of 911 adult ticks, collected from livestock in endemic areas were studied for presence of CCHFV by an immunofluorescence-hemocytes assay (IFHA) and a reverse transcription-polymerase chain reaction (RT-PCR). The detection rate of CCHFV in the tick population was 2.09%. The prevalence of the virus was determined between 2.01% and 4.83% in the regions of Kardzhali and Haskovo, respectively (Southeastern Bulgaria). In the Central part of the country CCHFV infestation of the ticks was observed in 1.46% (region of Stara Zagora). The results confirmed the mosaic dispersion of CCHFV in the investigated regions. The principal infection vector in the surveyed areas was confirmed to be Hyalomma marginatum marginatum. Rhipicephalus sanguineus and Ixodes ricinus were also detected and may play a role in the transmission of CCHFV. Species distribution of CCHFV-positive ticks was as follows: H. m. marginatum-4.93%; R. sanguineus-2.33%; I. ricinus-1.02%. The combination of IFHA and RT-PCR that are used in this study are useful tools in the algorithm for monitoring endemic areas in Bulgaria.

In Bulgaria, vaccination coverage against the SARS-CoV-2 virus is low. The reasons for this fact are many and varied. The aim of the present study was to establish what the attitudes towards the COVID-19 vaccination process are among students from various specialties from several Bulgarian universities. In this research, 600 students participated, divided into two groups: Doctor of Medicine (MD) students (n = 300) and non-MD students, i.e., students of specialties, such as mathematics, engineering, finance and economics, law, human sciences, etc. (n = 300). Each respondent completed a questionnaire which was divided into three parts with closed questions. The mean age of all students was 21.19 ± 1.87 years (95% CI: 20.48–21.90). The female sex dominated among the analyzed participants (sex ratio: female/male = 1/0.85). Nearly 62% (371/600) of individuals declared that they have been COVID-19 vaccinated with at least one dose (p < 0.001). Overall, 33% of the participants sought information on vaccines from video sharing platforms and 36.0% (216/600) from social media platforms. From the conducted multivariable logistic regression the odds of vaccination against COVID-19 were 6.225 times higher in individuals with a positive attitude towards these vaccines than in people with a negative attitude towards them (p < 0.001). We have found that those students who trust the international health organizations had an OR of 2.365 (p = 0.004) to be SARS-CoV-2 vaccinated. We estimated that the odds of vaccination against SARS-CoV-2 among children were 4.794 times higher in parents (students) who had been vaccinated than in non-vaccinated parents (students) (p < 0.001). Our results could support the national public health organizations, the national educational/scientific systems, and the management of Bulgarian universities in making future decisions about the field of COVID-19 control and prevention.

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In this paper we study the impact of the hidden cases of Covid-19 spread in Bulgaria by means of the SEIR model, in the period December 15, 2021 – until March 2022. In particular, the numerical experiments based on the hidden cases till mid-January, provide a forecast of the peak of the infectious curve about February 8, 2022, and reaching the maximum of about 90 000 cases. The forecast shows that end of the epidemics (in Bulgaria) would be in mid-May, 2022. This forecast is compared to the previous forecasts based on the same data excluding hidden cases; they have shown that the peak will be about February 28, reaching about 75 000 cases and will vanish until end of May. As seen in Fig. 3, our forecast of the end of the particular wave of epidemics shows just two weeks difference with what happened in real life – the wave ended in the first week of June. It is curious, that though the peak of the curve in thehidden cases approach has shifted to February 8, the cumulative number of cases in both approaches is nearly the same. More details on the methods used in the present paper and the non-hidden cases study, are provided as well.

Background: In the response to the current COVID-19 pandemic caused by the novel SARS-CoV-2, one of the groups at higher risk were healthcare workers (HCWs), especially those who worked on the frontline. The presence of SARS-CoV-2 specific IgG antibodies (seropositivity) in certain populations provides better understanding of virus circulation and transmission. Our aim was to study the seroprevalence rates of anti-SARS-CoV-2 antibodies among a group of healthcare workers before and after vaccination/COVID-19 infection. Material and Methods: We determined the presence of SARS-CoV-2 specific IgG and IgA antibodies against S-antigen of by ELISA method. In this study, we enrolled 74 healthcare workers and three months later, 48 of the participants were followed up. At the baseline, none of the participants was vaccinated or had suffered COVID-19.  Results: SARS-Cov-2 specific IgG antibodies were found in 32.4% of the participants. Higher prevalence of class IgA antibodies – 44.6% was detected. All samples that were IgG seropositive were also positive or borderline for IgA antibodies. Overall, virus-specific antibodies were not detected in 40.6% of HCWs in the group. During the follow-up (after vaccination and/or COVID-19 infection) high rates of both IgG and IgA seroprevalence were established. SARS-C0V-2 specific IgG antibodies were detected in 95.8% of the participants. Statistically significant difference was found in the levels of IgG and IgA antibodies both before and after vaccination, p<0.0001. Conclusions: Based on detection of anti-SARS-CoV-2 IgG antibodies, seroprevalence of 32.4% was established in an unvaccinated group of HCWs. Our survey demonstrated that asymptomatic COVID-19 infection may induce weaker humoral immune response, with production of IgA but not of IgG antibodies.

Световно разпространената зооноза Ку-треска се причинява от вътреклетъчния микроорганизъм Coxiella burnetii. Заболяването е ендемично за нашата страна и има две форми на протичане-остра и хронична. Поради неспецифичната симптоматика на Ку-треската поставянето на точна диагноза и правилно лечение са затруднени. В исторически план лечението на заболяването е претърпяло много промени, свързани с различни in vitro модели за проучване на чувствителността на Coxiella burnetii към антибиотични комбинации. За съвременното лечение на острата форма на Qтреската (Ку-треската) при възрастни се използва 100 mg доксициклин два пъти дневно за 14 дена, а при бременни се препоръчва ко-тримоксазол (триметоприм/сулфаметоксазол: 160 mg / 800 mg) два пъти дневно до последните шест седмици на бременността. Актуалната терапия на хроничната форма на заболяването включва 100 mg доксициклин два пъти дневно, комбинирани с хидроксихлорохин три пъти дневно при 200 mg на доза в продължение на най-малко 18 месеца.

Q fever, which is caused by Coxiella burnetii, a small, pleomorphic intracellular bacterium, is the most widespread zoonosis in the world. The chronic form of the disease can lead to disability and death. Rapid diagnosis of Q fever is needed in order that effective treatment can be initiated. The conventional retrospective diagnosis of Q fever, based on serology, is useless for the treatment of afflicted patients. Thus, molecular methods have been created to close the diagnostic gap between the onset of the disease and the presence of specific antibodies in serum. A polymerase chain reaction is a suitable and reliable method with high sensitivity and specificity, but it requires expensive equipment and post-amplification protocol. Loop-mediated isothermal amplification (LAMP) is an isothermal technique, conducted at constant temperature that can amplify a negligible amount of DNA to more than 109 copies within one hour, using special primers and polymerase. We have tested the sensitivity and specificity of LAMP in the detection of C. burnetii. The mean positive rate of LAMP and polymerase chain reaction in patients was 100% and 74%, respectively. LAMP reacted negatively with non-C. burnetii pathogens and non-infected blood samples. We conclude that LAMP is a sensitive and specific technique for the detection of C. burnetii and has advantages over serological methods and PCR that make it attractive for diagnosing Q fever in countries around the world.