Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. Transmission of HEV mainly occurs via the fecal-oral route (ingesting contaminated water or food) or by contact with infected animals and their raw meat products. Some animals, such as pigs, wild boars, sheep, goats, rabbits, camels, rats, etc., are natural reservoirs of HEV, which places people in close contact with them at increased risk of HEV disease. Although hepatitis E is a self-limiting infection, it could also lead to severe illness, particularly among pregnant women, or chronic infection in immunocompromised people. A growing number of studies point out that HEV can be classified as a re-emerging virus in developed countries. Preventative efforts are needed to reduce the incidence of acute and chronic hepatitis E in non-endemic and endemic countries. There is a recombinant HEV vaccine, but it is approved for use and commercially available only in China and Pakistan. However, further studies are needed to demonstrate the necessity of applying a preventive vaccine and to create conditions for reducing the spread of HEV. This review emphasizes the hepatitis E virus and its importance for public health in Europe, the methods of virus transmission and treatment, and summarizes the latest studies on HEV vaccine development.

The prevalence of hepatitis E virus (HEV) in the Bulgarian population remains underestimated. The aim of the present study was to evaluate age and gender trends in HEV prevalence in the heterogeneous Bulgarian population. Stored serum samples from blood donors and different patient sub-populations—kidney recipients (KR), patients with Guillain–Barre syndrome (GBS), Lyme disease (LD), patients with liver involvement and a clinical diagnosis other than viral hepatitis A and E (non-AE), hemodialysis (HD) and HIV-positive patients (HIV)—were retrospectively investigated for markers of past and recent/ongoing HEV infection. The estimated overall seroprevalence of past infection was 10.6%, ranging from 5.9% to 24.5% for the sub-populations evaluated, while the seroprevalence of recent/ongoing HEV infection was 7.5%, ranging from 2.1% to 20.4%. The analysis of the individual sub-populations showed a different prevalence with respect to sex. In regard to age, the cohort effect was preserved, as a multimodal pattern was observed only for the GBS sub-population. Molecular analysis revealed HEV 3f and 3e. The type of the population is one of the main factors on which the anti-HEV prevalence depends, highlighting the need for the development of guidelines related to the detection and diagnosis of HEV infection with regard to specific patient populations.

West Nile fever (WNF) is a vector-borne infection caused by a Flavivirus-West Nile virus (WNV). WNV is transmitted by mosquitoes, and birds are the major natural reservoir. A recent increase in the number of the WNF cases has been reported in Europe, the Balkans, and Bulgaria. We herein present the clinical course, laboratory and imaging findings of three patients – a female and two male patients, who were diagnosed with WNF. They were investigated in an epidemiological study, and by using clinical observation, laboratory and microbiological methods, serological tests for specific anti-WNV antibodies detection, molecular biology techniques (polymerase chain reaction, PCR), computed tomography (CT) and magnetic resonance imaging (MRI). The patients presented with fever, headache, drowsiness, and dizziness and anti-WNV antibodies were detected in their serum samples. WNV-RNA was found in a blood sample from the female patient. Both anti-WNV IgM and Herpes simplex virus-1 DNA were detected in a cerebrospinal fluid sample from one of the men. The three patients recovered from the disease after a long convalescent period. WNF has no specific signs, laboratory and imaging findings and could be a life-threatening condition, leading to serious complications. Therefore, WNF should be taken into consideration during the summer when the vector of the infection is active.

Epstein-Barr virus is a widely spread Herpesvirus. Primary EBV infection affects children and young people, inducing haematological changes, with lymphocytosis being the most common. Moderate symptomless thrombocytopenia is found in 50% of the patients, however, severe thrombocytopenia is exceptionally rare. We present a case report of a 20-year-old man with an acute EBV infection, severe thrombocytopenia, and no signs of infectious mononucleosis.

Background/Objectives: Monkeypox (mpox) is currently the most common orthopoxvirus (OPXV) zoonotic disease, and, since 2022, there has been atypical person-to-person transmission observed in non-endemic countries. The present study aimed to investigate the frequency of monkeypox virus (MPXV) and OPXV DNA detection in recommended and alternative clinical materials taken during the acute and convalescent phases of infection in Bulgarian patients. Methods: The study included laboratory investigation by real time PCR of 181 clinical samples from 42 Bulgarian patients with possible mpox infections. Results: MPXV DNA was detected in 23/181 (12.71%), and OPXV DNA in 20/181 (11.05%) clinical samples. There were six mpox-confirmed patients aged 23 to 44. At the highest frequency, MPXV and OPXV DNA were detected in samples of vesicular contents (6/6) and nasal/oropharyngeal secretions (5/6 and 4/6) during the first three days from the appearance of clinical symptoms. We demonstrated MPXV and OPXV DNA in alternative samples (urine, feces, ejaculate, and saliva), and in follow-up patient samples, taken two weeks after mpox confirmation in the convalescent phase (vesicular contentsand urine). Conclusions: Our findings suggested that MPXV may be detected in a larger set of clinical materials, including alternatives, where the virus can persist for more than two weeks.