Tick-borne viral encephalitis in Finland. The clinical features of Kumlinge disease during 1959-1987

[Arbovirus - a threat to transfusion safety in Spain: a narrative review]

Arboviruses represent a threat to transfusion safety for several reasons: the presence of vectors and the notification of autochthonous cases in our region, the recent increase in the number of cases transmitted through blood and/or blood component transfusion, the high prevalence rates of RNA of the main arboviruses in asymptomatic blood donors, and their ability to survive processing and storage in the different blood components. In an epidemic outbreak caused by an arbovirus in our region, transfusion centres can apply different measures: reactive measures, related to donor selection or arbovirus screening, and proactive measures, such as pathogen inactivation methods. The study of the epidemiology of the main arboviruses and understanding the effectiveness of the different measures that we can adopt are essential to ensure that our blood components remain safe.

Defining the "Correlate(s) of Protection" to tick-borne encephalitis vaccination and infection - key points and outstanding questions

Tick-borne Encephalitis (TBE) is a severe disease of the Central Nervous System (CNS) caused by the tick-borne encephalitis virus (TBEV). The generation of protective immunity after TBEV infection or TBE vaccination relies on the integrated responses of many distinct cell types at distinct physical locations. While long-lasting memory immune responses, in particular, form the basis for the correlates of protection against many diseases, these correlates of protection have not yet been clearly defined for TBE. This review addresses the immune control of TBEV infection and responses to TBE vaccination. Potential correlates of protection and the durability of protection against disease are discussed, along with outstanding questions in the field and possible areas for future research.

Tick-Borne Encephalitis Vaccine: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

Tick-borne encephalitis (TBE) virus is focally endemic in parts of Europe and Asia. The virus is primarily transmitted to humans by the bites of infected

Ixodes species ticks but can also be acquired less frequently by alimentary transmission. Other rare modes of transmission include through breastfeeding, blood transfusion, solid organ transplantation, and slaughtering of viremic animals. TBE virus can cause acute neurologic disease, which usually results in hospitalization, often permanent neurologic or cognitive sequelae, and sometimes death. TBE virus infection is a risk for certain travelers and for laboratory workers who work with the virus. In August 2021, the Food and Drug Administration approved Ticovac TBE vaccine for use among persons aged ≥1 year. This report summarizes the epidemiology of and risks for infection with TBE virus, provides information on the immunogenicity and safety of TBE vaccine, and summarizes the recommendations of the Advisory Committee on Immunization Practices (ACIP) for use of TBE vaccine among U.S. travelers and laboratory workers.

The risk for TBE for most U.S. travelers to areas where the disease is endemic is very low. The risk for exposure to infected ticks is highest for persons who are in areas where TBE is endemic during the main TBE virus transmission season of April–November and who are planning to engage in recreational activities in woodland habitats or who might be occupationally exposed. All persons who travel to areas where TBE is endemic should be advised to take precautions to avoid tick bites and to avoid the consumption of unpasteurized dairy products because alimentary transmission of TBE virus can occur. TBE vaccine can further reduce infection risk and might be indicated for certain persons who are at higher risk for TBE. The key factors in the risk-benefit assessment for vaccination are likelihood of exposure to ticks based on activities and itinerary (e.g., location, rurality, season, and duration of travel or residence). Other risk-benefit considerations should include 1) the rare occurrence of TBE but its potentially high morbidity and mortality, 2) the higher risk for severe disease among certain persons (e.g., older persons aged ≥60 years), 3) the availability of an effective vaccine, 4) the possibility but low probability of serious adverse events after vaccination, 5) the likelihood of future travel to areas where TBE is endemic, and 6) personal perception and tolerance of risk

ACIP recommends TBE vaccine for U.S. persons who are moving or traveling to an area where the disease is endemic and will have extensive exposure to ticks based on their planned outdoor activities and itinerary. Extensive exposure can be considered based on the duration of travel and frequency of exposure and might include shorter-term (e.g., <1 month) travelers with daily or frequent exposure or longer-term travelers with regular (e.g., a few times a month) exposure to environments that might harbor infected ticks. In addition, TBE vaccine may be considered for persons who might engage in outdoor activities in areas where ticks are likely to be found, with a decision to vaccinate made on the basis of an assessment of their planned activities and itinerary, risk factors for a poor medical outcome, and personal perception and tolerance of risk. In the laboratory setting, ACIP recommends TBE vaccine for laboratory workers with a potential for exposure to TBE virus

Tick-Borne Encephalitis-Review of the Current Status

The tick-borne encephalitis virus (TBEV) is the arboviral etiological agent of tick-borne encephalitis (TBE), considered to be one of the most important tick-borne viral diseases in Europe and Asia. In recent years, an increase in the incidence of TBE as well as an increasing geographical range of the disease have been noted. Despite the COVID-19 pandemic and the imposition of restrictions that it necessitated, the incidence of TBE is rising in more than half of the European countries analyzed in recent studies. The virus is transmitted between ticks, animals, and humans. It seems that ticks and small mammals play a role in maintaining TBEV in nature. The disease can also affect dogs, horses, cattle, and small ruminants. Humans are incidental hosts, infected through the bite of an infected tick or by the alimentary route, through the consumption of unpasteurized milk or milk products from TBEV-infected animals. TBEV infections in humans may be asymptomatic, but the symptoms can range from mild flu-like to severe neurological. In Europe, cases of TBE are reported every year. While there is currently no effective treatment for TBE, immunization and protection against tick bites are critical in preventing this disease.

Arboviral Risk Associated with Solid Organ and Hematopoietic Stem Cell Grafts: The Prophylactic Answers Proposed by the French High Council of Public Health in a National Context

Diseases caused by arboviruses are on the increase worldwide. In addition to arthropod bites, most arboviruses can be transmitted via accessory routes. Products of human origin (labile blood products, solid organs, hematopoietic stem cells, tissues) present a risk of contamination for the recipient if the donation is made when the donor is viremic. Mainland France and its overseas territories are exposed to a complex array of imported and endemic arboviruses, which differ according to their respective location. This narrative review describes the risks of acquiring certain arboviral diseases from human products, mainly solid organs and hematopoietic stem cells, in the French context. The main risks considered in this study are infections by West Nile virus, dengue virus, and tick-borne encephalitis virus. The ancillary risks represented by Usutu virus infection, chikungunya, and Zika are also addressed more briefly. For each disease, the guidelines issued by the French High Council of Public Health, which is responsible for mitigating the risks associated with products of human origin and for supporting public health policy decisions, are briefly outlined. This review highlights the need for a "One Health" approach and to standardize recommendations at the international level in areas with the same viral epidemiology.

Tick-borne encephalitis in pediatrics: An often overlooked diagnosis

Tick-borne encephalitis (TBE) is a vector-borne disease caused by a flavivirus, the tick-borne encephalitis virus (TBEV), and transmitted by the bite of infected Ixodes ricinus ticks. The European subtype (TBEV-Eu) is endemic in 27 European countries. During the last decade, increased TBE incidence was observed in many countries, including some of those believed to be of low endemicity/devoid of TBEV circulation. However, data dealing with TBE in children are far less profuse than with adults. Historically, children are known to have mild TBEV infection with favorable outcomes. That said, recent case reports and observational studies on pediatric cohorts have challenged this point of view. Like adults, children may present severe forms and fail to completely recover following TBE infection, at times leading to long-term cognitive impairment. In this review, we comprehensively describe the incidence, exposure factors, and transmission routes of TBEV in children, as well as the clinical and biological manifestations of TBE and imaging findings in this population. We also harness new data on long-term outcomes and sequelae in pediatric cohorts. Finally, we provide an overview of vaccination recommendations for children in European countries.

Co-Circulation of West Nile, Usutu, and Tick-Borne Encephalitis Viruses in the Same Area: A Great Challenge for Diagnostic and Blood and Organ Safety

Viral infections caused by viruses from the family Flaviviridae such as Zika (ZIKV), Dengue (DENV), yellow fever (YFV), tick-borne encephalitis (TBEV), West Nile (WNV), and Usutu (USUV) are some of the most challenging diseases for recognition in clinical diagnostics and epidemiological tracking thanks to their short viremia, non-specific symptoms, and high cross-reactivity observed in laboratory techniques. In Central Europe, the most relevant endemic flaviviruses are mosquito-borne WNV and USUV, and tick-borne TBEV. All three viruses have been recognised to be responsible for human neuroinvasive diseases. Moreover, they are interrupting the blood and transplantation safety processes, when the great efforts made to save a patient's life could be defeated by acquired infection from donors. Due to the trend of changing distribution and abundance of flaviviruses and their vectors influenced by global change, the co-circulation of WNV, USUV, and TBEV can be observed in the same area. In this perspective, we discuss the problems of flavivirus diagnostics and epidemiology monitoring in Slovakia as a model area of Central Europe, where co-circulation of WNV, USUV, and TBEV in the same zone has been recently detected. This new situation presents multiple challenges not only for diagnostics or surveillance but particularly also for blood and organ safety. We conclude that the current routinely used laboratory diagnostics and donor screening applied by the European Union (EU) regulations are out of date and the novel methods which have become available in recent years, e.g., next-gene sequencing or urine screening should be implemented immediately.

Systematic review on the non-vectorial transmission of Tick-borne encephalitis virus (TBEv)

Tick-borne encephalitis (TBE) is an infection caused by the Tick-borne encephalitis virus (TBEv) and it is common in Europe. The virus is predominantly transmitted by ticks, but other non-vectorial modes of transmission are possible. This systematic review synthesises the epidemiological impact of non-vectorial modes of TBEv transmission in Europe. 41 studies were included comprising of 1308 TBE cases. Alimentary (36 studies), handling infected material (3 studies),  blood-borne (1 study), solid organ transplant (1 study) were identified as potential routes of TBEv transmission; however, no evidence of vertical transmission from mother to offspring was reported (2 studies). Consumption of unpasteurised milk/milk products was the most common vehicle of transmission and significantly increased the risk of TBE by three-fold (pooled RR 3.05, 95% CI 1.53 to 6.11; 4 studies). This review also confirms handling infected material, blood-borne and solid organ transplant as potential routes of TBEv transmission. It is important to tracing back to find the vehicle of the viral infection and to promote vaccination as it remains a mainstay for the prevention of TBE.

Transfusion-transmitted arboviruses: Update and systematic review

Background

The detection of the first cases of transfusion-transmitted West Nile virus in 2002 posed a new challenge for transfusion safety. Institutions like the World Health Organization have stated that blood transfusion centers need to know the epidemiology of the different emerging infectious agents and their impact on blood transfusion. The aim of the study is to review the published cases of arbovirus transmission through transfusion of blood or blood components and to analyze their main clinical and epidemiological characteristics.

Material and methods

Systematic literature searches were conducted in MEDLINE, Embase and Scopus. Pairs of review authors selected a variety of scientific publications reporting cases of transfusion-transmitted arboviruses. Main clinical and epidemiological characteristics were reviewed of the cases described. The study protocol was registered in PROSPERO CRD42021270355.

Results

A total of 74 cases of transfusion-transmitted infections were identified from 10 arboviruses: West Nile virus (n = 42), dengue virus (n = 18), Zika virus (n = 3), yellow fever vaccine virus (n = 3), tick-borne encephalitis virus (n = 2), Japanese encephalitis virus (n = 2), Powassan virus (n = 1), St. Louis encephalitis virus (n = 1), Ross River virus (n = 1) and Colorado tick fever virus (n = 1). The blood component most commonly involved was red blood cells (N = 35, 47.3%; 95% confidence interval [CI] 35.9% to 58.7%). In 54.1% (N = 40; 95% CI: 42.7%-65.47%) of the cases, the recipient was immunosuppressed. Transmission resulted in death in 18.9% (N = 14; 95% CI: 10.0%-27.8%) of the recipients. In addition, 18 additional arboviruses were identified with a potential threat to transfusion safety.

Discussion

In the last 20 years, the number of published cases of transfusion-transmitted arboviruses increased notably, implicating new arboviruses. In addition, a significant number of arboviruses that may pose a threat to transfusion safety were detected. In the coming years, it is expected that transmission of arboviruses will continue to expand globally. It is therefore essential that all responsible agencies prepare for this potential threat to transfusion safety.

The transfusion of blood and blood components entails some risks and potential complications, chief among them the transmission of infectious agents. Organizations like the American Association of Blood Banks have warned of the risks posed by emerging and re-emerging viruses for transfusion safety and have classified transmission of several arboviruses as a high or very high risk to the transfusion of blood and blood components. Following recommendations by the World Health Organization (WHO), this study aims to enable safe blood transfusion services, by making available the latest updated information of transfusion-transmitted arboviruses and comprehensive knowledge of the current epidemiology of reported cases.

Research revealed case reports of transfusion transmission of 10 arboviruses, with West Nile virus and dengue virus as the most prevalent. Main clinical characteristics of reported cases were collected, including the type of blood component transfused and the state of immunosuppression of the recipient. Research also revealed 18 additional arboviruses with potential risk of transmission through other direct transmission routes. This systematic review provides an updated overview of the clinical characteristics of reported cases of transfusion-transmitted arboviruses. It is the most complete record published to date that assesses the risk posed by arboviruses to blood transfusion.

Alimentary Infections by Tick-Borne Encephalitis Virus

Tick-borne encephalitis virus (TBEV) causes serious the neurological disease, tick-borne encephalitis (TBE). TBEV can be transmitted to humans by ticks as well as by the alimentary route, which is mediated through the consumption of raw milk products from infected ruminants such as sheep, goats, and cows. The alimentary route of TBEV was recognized in the early 1950s and many important experimental studies were performed shortly thereafter. Nowadays, alimentary TBEV infections are recognized as a relevant factor contributing to the overall increase in TBE incidences in Europe. This review aims to summarize the history and current extent of alimentary TBEV infections across Europe, to analyze experimental data on virus secretion in milk, and to review possible alimentary infection preventive measures.

[Gestion of arboviral alerts: Experience feedback from the Secproch working group of the French "Haut Conseil de la santé publique" (2019-2021)]

The Secproch working group (for "sécurité des produits issus du corps humain") was created in 2019 within the « Haut Conseil de la santé publique » (HCSP) for addressing all the questions related to labile blood products, organs, tissues, cells (OTC) and gametes issued from human body. It is notably in charge of the management of alerts regarding arbovirus infections. These infections due to arthropod-transmitted viruses are responsible for emergence and reemergence, notably in the context of global warming. This review relates the alerts taken into consideration by the Secproch group between 2019 and 2021 following three pathologies due to Flaviviridae : dengue, West Nile virus (WNV) infection and tick-borne encephalitis (TBE). The dengue alerts have occurred in French Indies where the virus is endemic/epidemic, Reunion Island where the population was naïve until 2018 towards the virus, and the metropole where foci of autochthonous cases are observed sporadically. The WNV infection was responsible of both human and equine cases in 2019 in the South of France but with intensity much less than in 2018. At last, the TBE virus was at the origin of a cluster of about 40 cases in the Ain department following a contamination by crude non-pasteurized goat cheese. This review offers the opportunity to reevaluate the risks linked to these three viruses through blood products and organs/tissues/cells and to precise the means recommended by HCSP to secure these products.

Clinical Characteristics of Patients with Tick-Borne Encephalitis (TBE): A European Multicentre Study from 2010 to 2017

Tick-borne encephalitis (TBE) virus is a major cause of central nervous system infections in endemic countries. Here, we present clinical and laboratory characteristics of a large international cohort of patients with confirmed TBE using a uniform clinical protocol. Patients were recruited in eight centers from six European countries between 2010 and 2017. A detailed description of clinical signs and symptoms was recorded. The obtained information enabled a reliable classification in 553 of 555 patients: 207 (37.3%) had meningitis, 273 (49.2%) meningoencephalitis, 15 (2.7%) meningomyelitis, and 58 (10.5%) meningoencephalomyelitis; 41 (7.4%) patients had a peripheral paresis of extremities, 13 (2.3%) a central paresis of extremities, and 25 (4.5%) had single or multiple cranial nerve palsies. Five (0.9%) patients died during acute illness. Outcome at discharge was recorded in 298 patients. Of 176 (59.1%) patients with incomplete recovery, 80 (27%) displayed persisting symptoms or signs without recovery expectation. This study provides further evidence that TBE is a severe disease with a large proportion of patients with incomplete recovery. We suggest monitoring TBE in endemic European countries using a uniform protocol to record the full clinical spectrum of the disease.

Japanese Encephalitis Virus Transmitted Via Blood Transfusion, Hong Kong, China

Japanese encephalitis virus (JEV) is a mosquitoborne virus endemic to China and Southeast Asia that causes severe encephalitis in <1% of infected persons. Transmission of JEV via blood transfusion has not been reported. We report transmission of JEV via blood donation products from an asymptomatic viremic donor to 2 immunocompromised recipients. One recipient on high-dose immunosuppressive drugs received JEV-positive packed red blood cells after a double lung transplant; severe encephalitis and a poor clinical outcome resulted. JEV RNA was detected in serum, cerebrospinal fluid, and bronchoalveolar lavage fluid specimens. The second recipient had leukemia and received platelets after undergoing chemotherapy. This patient was asymptomatic; JEV infection was confirmed in this person by IgM seroconversion. This study illustrates that, consistent with other pathogenic flaviviruses, JEV can be transmitted via blood products. Targeted donor screening and pathogen reduction technologies could be used to prevent transfusion-transmitted JEV infection in highly JEV-endemic areas.

Amustaline (S-303) treatment inactivates high levels of Chikungunya virus in red-blood-cell components

BACKGROUND AND OBJECTIVES

Chikungunya virus (CHIKV) infections have been reported in all continents, and the potential risk for CHIKV transfusion-transmitted infections (TTIs) was demonstrated by the detection of CHIKV RNA-positive donations in several countries. TTIs can be reduced by pathogen inactivation (PI) of blood products. In this study, we evaluated the efficacy of amustaline and glutathione (S-303/GSH) to inactivate CHIKV in red-blood-cell concentrates (RBCs).

MATERIAL AND METHODS

Red-blood-cells were spiked with high level of CHIKV. Infectious titres and RNA loads were measured before and after PI treatment. Residual CHIKV infectivity was also assessed after five successive cell culture passages.

RESULTS

The mean CHIKV titres in RBCs before inactivation was 5·81 ± 0·18 log₁₀ 50% tissue culture infectious dose (TCID₅₀ )/mL, and the mean viral RNA load was 10·49 ± 0·15 log₁₀ genome equivalent (GEq)/mL. No CHIKV TCID was detected after S-303 treatment nor was replicative CHIKV particles and viral RNA present after five cell culture passages of samples obtained immediately after S-303 treatment.

CONCLUSION

Chikungunya virus was previously shown to be inactivated by the PI technology using amotosalen and ultraviolet A light for the treatment of plasma and platelets. This new study demonstrates that S-303/GSH can inactivate high titres of CHIKV in RBCs.

Surveillance of endemic foci of tick-borne encephalitis in Finland 1995-2013: evidence of emergence of new foci

The geographical risk areas for tick-borne encephalitis (TBE) in Finland remained the same until the beginning of the 21st century, but a considerable geographical expansion has been observed in the past 10 years. In order to support public health measures, the present study describes the number of laboratory-confirmed TBE cases and laboratory tests conducted and the associated trends by hospital district, with a particular emphasis on the suspected geographical risk areas. An additional investigation was conducted on 1,957 clinical serum samples throughout the country taken from patients with neurological symptoms to screen for undiagnosed TBE cases. This study identified new TBE foci in Finland, reflecting the spread of the disease into new areas. Even in the most endemic municipalities, transmission of TBE to humans occurred in very specific and often small foci. The number of antibody tests for TBE virus more than doubled (an increase by 105%) between 2007 and 2013. Analysis of the number of tests also revealed areas in which the awareness of clinicians may be suboptimal at present. However, it appears that underdiagnosis of neuroinvasive TBE is not common.

[New viral risks in blood transfusion by 2016]

Viral safety remains a major concern in transfusion of blood products. Over years, the control measures applied to blood products were made more and more sophisticated; however, the number of infectious agents, and notably of viruses, that can be transmitted by transfusion is increasing continuously. The aim of this review paper is to actualize that published in the same journal by the same authors in 2011 with more details on some of actual vs virtual viral threats that were identified recently in the field of blood transfusion. The main subjects that are covered successively concern the transmission via transfusion of hepatitis E virus, the frequency of transfusion transmitted arboviruses, transfusion at the time of the Ebola epidemics in West Africa, the debated role of Marseillevirus (giant viruses infecting amoebae and suspected to infect human blood latently), and, finally, the recent report of the identification in blood donors of a new member of the Flaviviridae family. The addition of these new viral risks to those already identified-partially controlled or not-pleads for the urgent need to move forward to considering inactivation of infectious agents in blood products.

Tick-borne encephalitis: A review of epidemiology, clinical characteristics, and management

Tick-borne encephalitis is an infection of central nervous system caused by tick-borne encephalitis virus transmitted to humans predominantly by tick bites. During the last few decades the incidence of the disease has been increasing and poses a growing health problem in almost all endemic European and Asian countries. Most cases occur during the highest period of tick activity, in Central Europe mainly from April to November. Tick-borne encephalitis is more common in adults than in children. Clinical spectrum of the disease ranges from mild meningitis to severe meningoencephalitis with or without paralysis. Rare clinical manifestations are an abortive form of the disease and a chronic progressive form. A post-encephalitic syndrome, causing long-lasting morbidity that often affects the quality of life develops in up to 50% of patients after acute tick-borne encephalitis. Clinical course and outcome vary by subtype of tick-borne encephalitis virus (the disease caused by the European subtype has milder course and better outcome than the disease caused by Siberian and Far-Easter subtypes), age of patients (increasing age is associated with less favorable outcome), and host genetic factors. Since clinical features and laboratory results of blood and cerebrospinal fluid are nonspecific, the diagnosis must be confirmed by microbiologic findings. The routine laboratory confirmation of the tick-borne encephalitis virus infection is based mainly on the detection of specific IgM and IgG antibodies in serum (and cerebrospinal fluid), usually by enzyme-linked immunosorbent assay. There is no specific antiviral treatment for tick-borne encephalitis. Vaccination can effectively prevent the disease and is indicated for persons living in or visiting tick-borne encephalitis endemic areas.

Come fly with me: review of clinically important arboviruses for global travelers

Western tourists are increasingly traveling to exotic locations often located in tropical or subtropical regions of the world. The magnitude of international travel and the constantly changing dynamics of arbovirus diseases across the globe demand up-to-date information about arbovirus threats to travelers and the countries they visit. In this review, the current knowledge on arbovirus threats to global travelers is summarized and prioritized per region. Based on most common clinical syndromes, currently known arboviruses can be grouped to develop diagnostic algorithms to support decision-making in diagnostics. This review systematically combines and structures the current knowledge on medically important travel-related arboviruses and illustrates the necessity of a detailed patient history (travel history, symptoms experienced, vaccination history, engaged activities, tick or mosquito bite and use of repellent and onset of symptoms), to guide the diagnosis.

Peripheral facial palsy in patients with tick-borne encephalitis

Although tick-borne encephalitis (TBE) has been recognized in Europe for more than 70 years and has been the topic of numerous reports, information on the involvement of facial nerves in the course of the disease is limited. Our study conducted at a single medical centre revealed that facial nerve involvement in the course of TBE in Central Europe is (i) infrequent--it was found in only 11 of 1218 (0.9%) consecutive adult patients diagnosed with TBE; (ii) manifests with unilateral or rarely bilateral peripheral facial palsy (PFP) (nine and two patients, respectively); (iii) appears late in the course of acute illness--in our patients 10-20 days after the onset of the meningoencephalitic phase of TBE, and often after defervescence (in 8/11 patients; 6-13 days after normalization of body temperature); (iv) develops more often in patients with more severe illness, i.e. more frequently in those with encephalitic than in those with meningitic clinical presentation, and more commonly in patients with monophasic than biphasic illness; and (v) has a favourable outcome--our patients had a clinically complete recovery from PFP within 7-90 (median 30) days after its onset. Moreover, the finding of Borrelia infection in 3/11 (27.3%) patients (diagnosis of confirmed Lyme neuroborreliosis was established in 1/11 patients and two patients fulfilled criteria for possible Lyme neuroborreliosis) suggests that in countries where TBE and Lyme borreliosis are endemic, concomitant infection with Borrelia burgdorferi sensu lato should be considered and searched for in patients who develop PFP in the course of TBE.

[Emergent viral threats in blood transfusion]

Au cours des 20 dernières années, la sécurité en transfusion sanguine a fait de très grands progrès vis-à-vis du risque infectieux et notamment de celui représenté par les rétrovirus (HIV et HTLV) et les virus des hépatites B et C. L’objet de cette revue est de répertorier les risques viraux résiduels ou émergents qui seraient susceptibles d’entraîner de nouvelles contaminations chez les receveurs. À côté de nombreux autres virus (HHV-8, erythrovirus B19, virus des hépatites A et E…), une place toute particulière est faite aux arboviroses émergentes (infections à West Nile virus, dengue et chikungunya) qui menacent de toucher le territoire métropolitain suite à l’implantation en Europe du moustique Aedes albopictus, principal vecteur de la dengue et du chikungunya dans les régions tempérées. Un autre risque sanguin émergent, particulièrement au Royaume-Uni et en France, est constitué par le prion à l’origine de la forme variante de la maladie de Creutzfeldt-Jakob. La revue se termine par un rapide panorama des mesures qui sont susceptibles de contrôler ces émergences : exclusion des donneurs à risque, tests diagnostiques spécifiques de tel ou tel agent, déleucocytation des produits sanguins labiles et traitements physiques ou chimiques capables d’inactiver de façon non spécifique les agents infectieux potentiellement contaminants sans trop altérer les propriétés des composants sanguins. La capacité à maîtriser de façon prospective les nouveaux risques viraux au niveau transfusionnel représente un vrai défi pour préserver la confiance retrouvée des prescripteurs et des receveurs vis-à-vis des produits sanguins.

Viral meningoencephalitis: a review of diagnostic methods and guidelines for management

BACKGROUND

Viral encephalitis is a medical emergency. The prognosis depends mainly on the pathogen and host immunologic state. Correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury.

METHODS

We searched the literature from 1966 to 2009. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear, we have stated our opinion as good practice points.

RECOMMENDATIONS

Diagnosis should be based on medical history and examination followed by CSF analysis for protein and glucose levels, cellular analysis, and identification of the pathogen by polymerase chain reaction amplification (recommendation level A) and serology (level B). Neuroimaging, preferably by MRI, is essential (level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be performed immediately, LP should be delayed only under unusual circumstances. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. Patients must be hospitalized with easy access to intensive care units. Specific, evidence-based, antiviral therapy, acyclovir, is available for herpes encephalitis (level A) and may also be effective for varicella-zoster virus encephalitis. Ganciclovir and foscarnet can be given to treat cytomegalovirus encephalitis, and pleconaril for enterovirus encephalitis (IV class evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective, and their use is controversial, but this important issue is currently being evaluated in a large clinical trial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Transfusion-transmitted arboviruses

There exists considerable risk for transfusion transmission of arboviruses due to short periods of asymptomatic viraemia in populations with variable and sometimes extremely high incidence of arboviral infections. Aside from West Nile virus, few arbovirus transfusion transmissions have been proven, mostly due to difficulties in ruling out vector-borne transmission in recipients with arbovirus disease. Nevertheless, arbovirus transfusion risk models and assessments of viraemia prevalence in blood donations indicate substantial transfusion transmission of dengue and Chikungunya viruses in epidemic areas. Many other arboviruses, several of which are importation risks in the Americas, Europe and Asia, also cause large outbreaks and threaten transfusion safety. Prevention largely depends on excluding donors from outbreak areas or implementation of highly sensitive nucleic acid amplification tests. Because of the increasing emergence of arboviral disease globally, it is prudent to prepare for both endemic and exotic arboviruses capable of producing large epidemics and subsequent transfusion transmission risk.

TBE in Åland Islands 1959–2005: Kumlinge disease

Tick-borne encephalitis, TBE, has been observed in Aland Islands (population 26,500) for more than 60 years. Because of the small population, the relative incidence is high. Antibodies to TBE virus have been found in ca. 5% of healthy blood donors, indicating that subclinical infection must be common. This study is a review of the symptoms and signs of all the 301 serologically verified cases of TBE seen in Aland during 1959-2005. It also aims at analysing any possible changes in the symptoms and signs of TBE over time. The annual number of patients has been from 1 to 26, and has increased over time. The clinical picture has not undergone any conspicuous changes during these years. A few patients have had permanent neurological damage. There were no certain deaths from TBE. Simple practical measures may be taken to diminish, but not to eliminate, the risk of tick bites. Vaccination of exposed people is recommended, and general vaccination against TBE has commenced in Aland, beginning 2006. This is expected to reduce the incidence of TBE among the population to almost nil, provided that new inhabitants are vaccinated and that booster vaccinations are carried out as required.

Tick-borne encephalitis

We review the epidemiological and clinical characteristics of tick-borne encephalitis, and summarise biological and virological aspects that are important for understanding the life-cycle and transmission of the virus. Tick-borne encephalitis virus is a flavivirus that is transmitted by Ixodes spp ticks in a vast area from western Europe to the eastern coast of Japan. Tick-borne encephalitis causes acute meningoencephalitis with or without myelitis. Morbidity is age dependent, and is highest in adults of whom half develop encephalitis. A third of patients have longlasting sequelae, frequently with cognitive dysfunction and substantial impairment in quality of life. The disease arises in patchy endemic foci in Europe, with climatic and ecological conditions suitable for circulation of the virus. Climate change and leisure habits expose more people to tick-bites and have contributed to the increase in number of cases despite availability of effective vaccines. The serological diagnosis is usually straightforward. No specific treatment for the disease exists, and immunisation is the main preventive measure.

Siberian subtype tickborne encephalitis virus, Finland

We isolated 11 Siberian subtype tickborne encephalitis virus (TBEV) strains from Ixodes persulcatus ticks from a TBEV-endemic focus in the Kokkola Archipelago, western Finland. Thus I. persulcatus and the Siberian TBEV are reported in a focus considerably northwest of their previously known range in eastern Europe and Siberia.

Study of the serological response after vaccination against tick-borne encephalitis in Sweden

The antibody response to vaccination against tick-borne encephalitis (TBE) with FSME-Immun Inject (Immuno AG/Baxter) was studied in 535 persons, mainly adults, attending a vaccination centre in Stockholm, Sweden. Emphasis was laid on long-term follow-up. Antibody activity was measured by three different serological test systems: a commercial ELISA kit, a hemagglutination inhibition (HI) test and a neutralization test (RFFIT). The neutralization test proved to be the most sensitive assay for the detection of the vaccine response, which was demonstrable in the majority of vaccinees (>90% after three and >98% after four and five vaccinations, respectively). ELISA and HI were less sensitive for antibody measurement during primary immunization. Neutralizing antibody activity persisted prior to the third dose in 77% of the vaccinees and prior to the fourth to sixth doses in 89-95% of the vaccinees. ELISA activity, but no neutralizing activity, was found in some individuals. Based on our data and previous experience of vaccine failures after two doses, a more condensed three-dose vaccination schedule may be advantageous and ought to be tested. The persistence of neutralizing antibodies justifies further studies of the antibody responses after the fourth dose for periods beyond the recommended 3-year booster intervals.

Viral encephalitis: a review of diagnostic methods and guidelines for management

Viral encephalitis is a medical emergency. The spectrum of brain involvement and the prognosis are dependent mainly on the specific pathogen and the immunological state of the host. Although specific therapy is limited to only several viral agents, correct immediate diagnosis and introduction of symptomatic and specific therapy has a dramatic influence upon survival and reduces the extent of permanent brain injury in survivors. We searched MEDLINE (National Library of Medicine) for relevant literature from 1966 to May 2004. Review articles and book chapters were also included. Recommendations are based on this literature based on our judgment of the relevance of the references to the subject. Recommendations were reached by consensus. Where there was lack of evidence but consensus was clear we have stated our opinion as good practice points. Diagnosis should be based on medical history, examination followed by analysis of cerebrospinal fluid for protein and glucose contents, cellular analysis and identification of the pathogen by polymerase chain reaction (PCR) amplification (recommendation level A) and serology (recommendation level B). Neuroimaging, preferably by magnetic resonance imaging, is an essential aspect of evaluation (recommendation level B). Lumbar puncture can follow neuroimaging when immediately available, but if this cannot be obtained at the shortest span of time it should be delayed only in the presence of strict contraindications. Brain biopsy should be reserved only for unusual and diagnostically difficult cases. All encephalitis cases must be hospitalized with an access to intensive care units. Supportive therapy is an important basis of management. Specific, evidence-based, anti-viral therapy, acyclovir, is available for herpes encephalitis (recommendation level A). Acyclovir might also be effective for varicella-zoster virus encephalitis, gancyclovir and foscarnet for cytomegalovirus encephalitis and pleconaril for enterovirus encephalitis (IV class of evidence). Corticosteroids as an adjunct treatment for acute viral encephalitis are not generally considered to be effective and their use is controversial. Surgical decompression is indicated for impending uncal herniation or increased intracranial pressure refractory to medical management.

Characterisation of human tick-borne encephalitis virus from Sweden

Viruses of the tick-borne encephalitis (TBE) antigenic complex, within the family Flaviviridae, cause a variety of diseases including uncomplicated febrile illness, meningo-encephalitis and haemorrhagic fever. Different wildlife species act as reservoir hosts with ixodid tick species as vectors. TBE virus (TBEV) causes 40-130 cases confirmed serologically in Sweden each year. Characteristics of TBEV strains circulating in Sweden have not been investigated previously and no viral sequence data has been reported. In the present study, virus strains were isolated from serum of patients with clinical symptoms consistent with acute TBEV infection. Serologic characterisation, using a panel of E-specific monoclonal antibodies and cross-neutralisation tests, indicated that the Swedish strains of TBEV, isolated 1958-1994, all belonged to the Western TBEV subtype, which includes the Austrian vaccine strain Neudoerfl. Genetic analysis of a partial E-sequence confirmed this close relationship: all Swedish TBEV strains belonged to the European lineage of the Western TBEV subtype, which includes the previously characterised strains Neudoerfl, Hypr, and Kumlinge. Further, three Swedish strains showed partial E-sequences identical to that of the Finnish Kumlinge strain, ten Swedish strains formed a well-supported separate cluster, whereas four others did not show any real clustering. No apparent correlation was observed in comparison of clinical parameters with genetic data or geographic origin of the strains.

Tick-borne encephalitis--pathogenesis, clinical course and long-term follow-up

The prospective studies available today confirm the experience gained from several retrospective studies that TBE is a disease with a severe acute clinical course and considerable long-term morbidity. A defined post-encephalitic TBE syndrome exists, causing long-lasting morbidity that often affects the quality of life and sometimes also forces the individual to a change in life-style. The sequelae render high costs for individual patients and the society. Three clinical courses may be identified: one with complete recovery within 2 months, occurring in approximately one fourth of patients, one with protracted, mainly cognitive dysfunction, and one with persisting spinal nerve paralysis with or without other post-encephalitic symptoms. Up to 46% of patients are left with permanent sequelae at long-time follow-up, the most commonly reported residuals being various cognitive or neuropsychiatric complaints, balance disorders, headache, dysphasia, hearing defects, and spinal paralysis. This knowledge enhances the need for continued local epidemiological surveillance of TBE to form a basis for vaccination policies. Even though knowledge of the clinical course of TBE has improved in recent years, there are still several aspects of this disease that warrant further studies. These comprise the clinical picture and prognosis in children, an evaluation of different rehabilitation strategies, and an improved understanding of pathogenic mechanisms to permit the development of antiviral or, maybe more probable, immune modulatory treatment strategies.

Epidemiology and ecology of TBE relevant to the production of effective vaccines

This review focuses on the epidemiology and ecology of the tick-borne encephalitis (TBE) virus including all the factors influencing the ecology of the TBE virus, environmental and climatic conditions, the vectors and reservoir hosts and their interactions. Consequently, the structure and the conditions of natural foci of TBE are described, as well. Special emphasis is given on data regarding the virus prevalence in ticks in the field. In the second part of this review all the epidemiological and surveillance data of TBE in the 27 European countries and in the Far East with risk areas of TBE and in China and Japan are summarised. Therefore the review is a basis for travellers and inhabitants to get background information for their personal risk assessment.

Tickborne encephalitis in an area of high endemicity in lithuania: disease severity and long-term prognosis

Of 250 consecutively admitted patients with central nervous system (CNS) infections who were treated during a 1-year period, all 133 patients with tickborne encephalitis (TBE) were included in a prospective follow-up study. TBE presented as mild (meningeal) in 43.6% of patients and as moderate or severe (encephalitic) in 43.6% and 12.8% of patients, respectively. Paralytic disease was observed in 3.8% of the subjects, and cranial nerve injury was observed in 5.3%. One patient died of TBE. Permanent CNS dysfunction after 1 year was found in 30.8% of patients; in 8.5% of all TBE cases, severe disabilities required adjustment of daily activities. Corticosteroid treatment did not seem to improve outcome. A progressive course of TBE was noted in 2 patients. The risk of incomplete recovery was significantly higher among patients with the encephalitic form of TBE (odds ratio, 4.066; 95% confidence interval, 1.848-8.947). In conclusion, TBE is an important pathogen in CNS infection in the Kaunas region of Lithuania, and it causes long-lasting morbidity in one-third of cases.

Tick-borne diseases in transfusion medicine

Ticks are effective vectors of viral, bacterial, rickettsial and parasitic diseases. Many of the tick-borne diseases (TBDs) are of significance to transfusion medicine, either because of the risks they pose to the blood supply or the necessity for blood products required in their treatment. The transmission of tick-borne pathogens via blood transfusion is of global concern. However, among transfusion medicine practitioners, experience with most of these microorganisms is limited. Transfusion transmission of TBDs has been documented largely by means of single case reports. A better understanding of the epidemiology, biology and management of this group of diseases is necessary in order to assess the risks they pose to the blood supply and to help guide effective prevention strategies to reduce this risk. Unique methods are required to focus on donor selection, predonation questioning, mass screening and inactivation or eradication procedures. The role of the transfusion medicine service in their treatment also needs to be better defined. This article reviews the growing body of literature pertaining to this emerging field of transfusion medicine and offers some recommendations for transfusionists in dealing with TBDs.

[Tick-born encephalitis]

INTRODUCTION

Tick-borne encephalitis (TBE), a disease contracted through tick bites, is caused by a Flavivirus. Its geographical distribution comes from the geographical distribution of the reservoir of infection--i.e., mainly the tiny mammals living in the forests and bushes. The endemic area spreads from the Rhine to the Urals, from Scandinavia to Italy and Greece.

CURRENT KNOWLEDGE AND KEY POINTS

Symptoms usually evolve in three phases: at first a nonspecific phase with fever and myalgia, then an afebrile phase, and finally a phase with neurological manifestations, such as meningitis, meningoencephalitis and/or myelitis, and fever. Motor neurological sequelae are possible. The cases occurring in the East are characterized by their greater severity compared to those occurring in the West. The diagnosis, easily established given a history of a tick bite in an endemic area, is confirmed by the presence of specific IgM in the blood and/or cerebral spinal fluid.

FUTURE PROSPECT AND PROJECTS

There is no specific treatment. Prevention consists of individual prophylactic measures (self-examination and systematic extraction of ticks after exposure, use of repellents), and in immunization. The vaccine, prepared from inactivated viruses, should be used for target populations, that is, for people exposed to tick bites during their professional or leisure outdoor activities.

Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in Finland

Approximately 20 cases of tick-borne encephalitis (TBE) occur annually in Finland. The known endemic areas are situated mainly in the archipelago and coastal regions of Finland, with highest incidence in Aland islands. Ixodes ricinus panels collected in 1996-1997 from two endemic areas were screened for the presence of RNA. Two distinct RT-PCR methods were applied, and were shown to have an approximate detection limit of 10 focus forming doses (FFD)/100 microl. One out of 20 pools (a total of 139 ticks) from Helsinki Isosaari Island and one out of 48 pools (a total of 450 ticks) from Aland were positive with both methods, whereas the remaining pools were negative. The observed overall frequency (0.34%) in ticks in endemic areas of Finland, was similar to the low incidence found by virus isolation in mice in the 1960s (0.5%). Viral RNA was detectable in a diluted sample representing 0.005% of a positive pool of ten nymphs suggesting that the viral RNA load within an infected tick pool was approximately equivalent to 20,000-200,000 FFD. Sequence analysis did not show geographical clustering of the Finnish strains, suggesting an independent emergence of different TBE foci from the south. TBE virus RNA positive ticks were not found in I. ricinus panels consisting of 130 pools (726 ticks) from Helsinki city parks or 41 pools (197 ticks) from Võrmsi Island in Estonia.

Acute encephalitis from 1967 to 1991

We studied all the adult patients with acute encephalitis, 322 in all, in the Helsinki area, Finland, during the years 1967--1991. The average incidence was 1.4/100000 adults/year. The proportion of known and suggested etiologies in 5-year periods has risen from 36 (1967--71) to 59% (1987--91). Herpes simplex virus was identified most often (16%), followed by varicella-zoster (5%), mumps (4%), and influenza A viruses (4%). In addition, 20 other agents were identified. The leading cause of encephalitis in patients aged 65 years or more was varicella-zoster virus. Eighteen patients (5.6%) died. It appears that the etiology of encephalitis changes with age and with time. It is important to establish the etiological pattern, as this assists in prompt diagnosis, which is a prerequisite for successful therapy.