Diagnostic assays for Crimean-Congo hemorrhagic fever

Molecular and serological findings in suspected patients with Crimean-Congo hemorrhagic fever virus in Iran

Crimean-Congo hemorrhagic fever (CCHF) is an arthropod-borne disease of humans associated with a severe clinical picture, including hemorrhagic syndrome and a high mortality rate. CCHF virus is widely distributed throughout large areas of the world. To characterize the serological status in CCHF patients, paired clinical samples were collected from suspected CCHF patients and analyzed by microbiological and other laboratory analyses with the aim of: determining the presence of neutralizing antibodies against CCHF virus; investigating the cross-reactivity of these neutralizing antibodies against virus isolated from the same outbreak and against other available laboratory strain; and studying the relationship between the isolated virus with other virus by whole genome sequencing. Patients at Boo-Ali Hospital, Zahedan, Iran, with clinical symptoms ranging from mild to severe hemorrhagic fever were included in the study. Two serum samples were taken from each patient, the first as soon as the patient matched the criteria for CCHF notification and the second when the patient was discharged from hospital (2 weeks later). Commercial and in-house assays revealed a positive IgM signal in acute serum samples from six patients. A novel finding was that CCHF patients develop neutralizing antibodies soon after infection. Interestingly these antibodies were able to neutralize other CCHF virus strains too. The complete sequence of the Zahedan 2007 isolate, including the hitherto unknown first L-segment sequence, was identified using an original clinical sample from one patient with confirmed CCHF infection.

Single-Stranded RNA Viruses

In this chapter, we describe 73 zoonotic viruses that were isolated in Northern Eurasia and that belong to the different families of viruses with a single-stranded RNA (ssRNA) genome. The family includes viruses with a segmented negative-sense ssRNA genome (families Bunyaviridae and Orthomyxoviridae) and viruses with a positive-sense ssRNA genome (families Togaviridae and Flaviviridae). Among them are viruses associated with sporadic cases or outbreaks of human disease, such as hemorrhagic fever with renal syndrome (viruses of the genus Hantavirus), Crimean–Congo hemorrhagic fever (CCHFV, Nairovirus), California encephalitis (INKV, TAHV, and KHATV; Orthobunyavirus), sandfly fever (SFCV and SFNV, Phlebovirus), Tick-borne encephalitis (TBEV, Flavivirus), Omsk hemorrhagic fever (OHFV, Flavivirus), West Nile fever (WNV, Flavivirus), Sindbis fever (SINV, Alphavirus) Chikungunya fever (CHIKV, Alphavirus) and others. Other viruses described in the chapter can cause epizootics in wild or domestic animals: Geta virus (GETV, Alphavirus), Influenza A virus (Influenzavirus A), Bhanja virus (BHAV, Phlebovirus) and more. The chapter also discusses both ecological peculiarities that promote the circulation of these viruses in natural foci and factors influencing the occurrence of epidemic and epizootic outbreaks

Prevalence of Crimean-Congo hemorrhagic fever virus in healthy population, livestock and ticks in Kosovo

Crimean-Congo hemorrhagic fever (CCHF) is an acute, tick borne disease often associated with hemorrhagic presentations and high case fatality rate. Kosovo is a highly endemic area for CCHF, with a significant case fatality rate. The aim of our study was to determine the prevalence of CCHF in Kosovo. We tested 1105 serum samples from healthy population in both endemic and non-endemic areas in the country. Our results revealed a seroprevalence of 4.0% (range 0-9.3%) which is comparable to the seroprevalence in other countries. We show that seroprevalence is correlated to the disease incidence in each studied municipality. We also tested 401 animal sera (353 cow, 30 sheep, 10 goat and 8 chicken) in four endemic municipalities in Kosovo. We detected specific antibodies in all animals except in chicken. Seroprevalence in cows is comparable to other endemic areas and correlates to the seroprevalence in humans. No CCHF RNA could be detected in 105 tick samples obtained in 2012 and 2013. Sequencing of CCHFV positive ticks from 2001 revealed that the virus is most closely related to viral strains that were detected in CCHF patients from Kosovo. Results suggest that mild CCHF cases are most probably underdiagnosed and consequently that the burden of disease is higher than reported. Our study provides key information for CCHF surveillance and raises awareness for possible imported cases in CCHF non-endemic countries.

Recent advances in research on Crimean-Congo hemorrhagic fever

Crimean-Congo hemorrhagic fever (CCHF) is an expanding tick-borne hemorrhagic disease with increasing human and animal health impact. Immense knowledge was gained over the past 10 years mainly due to advances in molecular biology, but also driven by an increased global interest in CCHFV as an emerging/re-emerging zoonotic pathogen. In the present article, we discuss the advances in research with focus on CCHF ecology, epidemiology, pathogenesis, diagnostics, prophylaxis and treatment. Despite tremendous achievements, future activities have to concentrate on the development of vaccines and antivirals/therapeutics to combat CCHF. Vector studies need to continue for better public and animal health preparedness and response. We conclude with a roadmap for future research priorities.

European survey on laboratory preparedness, response and diagnostic capacity for Crimean-Congo haemorrhagic fever, 2012

Crimean-Congo haemorrhagic fever (CCHF) is an infectious viral disease that has (re-)emerged in the last decade in south-eastern Europe, and there is a risk for further geographical expansion to western Europe. Here we report the results of a survey covering 28 countries, conducted in 2012 among the member laboratories of the European Network for Diagnostics of 'Imported' Viral Diseases (ENIVD) to assess laboratory preparedness and response capacities for CCHF. The answers of 31 laboratories of the European region regarding CCHF case definition, training necessity, biosafety, quality assurance and diagnostic tests are presented. In addition, we identified the lack of a Regional Reference Expert Laboratory in or near endemic areas. Moreover, a comprehensive review of the biosafety level suitable to the reality of endemic areas is needed. These issues are challenges that should be addressed by European public health authorities. However, all respondent laboratories have suitable diagnostic capacities for the current situation.

Antibody responses and viral load in patients with Crimean-Congo hemorrhagic fever: a comprehensive analysis during the early stages of the infection

This study was performed to assess viral load, viral nucleocapsid (N), and glycoprotein precursor (GPC) antibodies in consecutive samples obtained from Crimean-Congo hemorrhagic fever patients to reveal viral replication kinetics and antiviral immune responses during the early stages of the infection. Among 116 samples from 20 individuals, 43.9% and 76.7% were positive for viral RNA and IgM/IgG antibodies, respectively, whereas both markers could be detected in 22.4%. Mean duration of viremia was 3 days (range: 1-6 days). N-IgM antibodies were identified as the initial serological marker during the infection, becoming detectable in a median of 2-3 days after disease onset, followed by GPC-IgM (4-6 days) and IgG antibodies (5-6 days). Clearance of viremia followed or coincided N-IgM response. Partial S gene sequences amplified in viremic patients were identical or closely related to previously characterized strains and grouped within European lineage I group II viruses via neighbor-joining analysis without significant amino acid substitutions.

Crimean-Congo hemorrhagic fever: history, epidemiology, pathogenesis, clinical syndrome and genetic diversity

Crimean-Congo hemorrhagic fever (CCHF) is the most important tick-borne viral disease of humans, causing sporadic cases or outbreaks of severe illness across a huge geographic area, from western China to the Middle East and southeastern Europe and throughout most of Africa. CCHFV is maintained in vertical and horizontal transmission cycles involving ixodid ticks and a variety of wild and domestic vertebrates, which do not show signs of illness. The virus circulates in a number of tick genera, but Hyalomma ticks are the principal source of human infection, probably because both immature and adult forms actively seek hosts for the blood meals required at each stage of maturation. CCHF occurs most frequently among agricultural workers following the bite of an infected tick, and to a lesser extent among slaughterhouse workers exposed to the blood and tissues of infected livestock and medical personnel through contact with the body fluids of infected patients. CCHFV is the most genetically diverse of the arboviruses, with nucleotide sequence differences among isolates ranging from 20% for the viral S segment to 31% for the M segment. Viruses with diverse sequences can be found within the same geographic area, while closely related viruses have been isolated in far distant regions, suggesting that widespread dispersion of CCHFV has occurred at times in the past, possibly by ticks carried on migratory birds or through the international livestock trade. Reassortment among genome segments during co-infection of ticks or vertebrates appears to have played an important role in generating diversity, and represents a potential future source of novel viruses. In this article, we first review current knowledge of CCHFV, summarizing its molecular biology, maintenance and transmission, epidemiology and geographic range. We also include an extensive discussion of CCHFV genetic diversity, including maps of the range of the virus with superimposed phylogenetic trees. We then review the features of CCHF, including the clinical syndrome, diagnosis, treatment, pathogenesis, vaccine development and laboratory animal models of CCHF. The paper ends with a discussion of the possible future geographic range of the virus. For the benefit of researchers, we include a Supplementary Table listing all published reports of CCHF cases and outbreaks in the English-language literature, plus some principal articles in other languages, with total case numbers, case fatality rates and all CCHFV strains on GenBank.

Crimean-Congo hemorrhagic fever: an overview

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral infection that is a serious threat to humans. The disease is widely distributed in Africa, Asia, and Europe and has developed into a serious public health concern. Humans become infected through the bites of ticks, by contact with a patient with CCHF, or by contact with blood or tissues from viremic livestock. Microvascular instability and impaired hemostasis are the hallmarks of the infection. Infection in human begins with nonspecific febrile symptoms, but may progress to a serious hemorrhagic syndrome with high mortality rates. Enzyme-linked immunoassay (ELISA) and polymerase chain reaction (PCR) are the most used and specific tests for the diagnosis. The mainstay of treatment is supportive. Although definitive studies are not available, ribavirin is suggested to be effective especially at the earlier phase of the infection. Uses of universal protective measures are the best way to avoid the infection. In this review, all aspects of CCHF are overviewed in light of the current literature.

The impact of Crimean-Congo hemorrhagic fever virus on public health

Climatic, environmental and economic changes, as well as the steadily increasing global trade and personal mobility provide ample opportunities for emerging pathogens with zoonotic potential to spread to previously unaffected countries. Crimean-Congo hemorrhagic fever virus (CCHFV) is considered to be one of the major emerging disease threats spreading to and within the European Union following an expanding distribution of its main vector, ticks of the genus Hyalomma. Every year more than 1000 human CCHF cases are reported from countries of southeastern Europe and Turkey. CCHFV can cause high case fatality rates and can be transmitted from human to human. There are no vaccine prophylaxis and therapeutic interventions available at present. Several EU-funded research projects focus currently on CCHFV which highlights the awareness for this problem at the European level. As public health deals with questions of prevention on a population level rather than healing and health on an individual level, the analysis of existing data plays a fundamental role to minimize its epidemic potential, by reducing infection risks, and to manage disease outbreaks. This review gives a summary of the current knowledge and data with focus at the interface between public health and CCHFV. Based on this knowledge, guidelines for the risk classification of a region and for outbreak prevention are given. This review will assist decision makers and public health authorities in understanding risk scenarios and in deciding on effective countermeasures, as well as human and veterinary scientists by highlighting existing gaps in knowledge.