1.0TBE Bookhttps://tbenews.com/tbeAdministrator adminhttps://tbenews.com/tbe/author/administrator-admin/rich600338<blockquote class="wp-embedded-content" data-secret="ySM3dCbPTR"><a href="https://tbenews.com/tbe/tbe12b32/">Sweden</a></blockquote><iframe sandbox="allow-scripts" security="restricted" src="https://tbenews.com/tbe/tbe12b32/embed/#?secret=ySM3dCbPTR" width="600" height="338" title="“Sweden” — TBE Book" data-secret="ySM3dCbPTR" frameborder="0" marginwidth="0" marginheight="0" scrolling="no" class="wp-embedded-content"></iframe><script> /*! This file is auto-generated */ !function(d,l){"use strict";l.querySelector&&d.addEventListener&&"undefined"!=typeof URL&&(d.wp=d.wp||{},d.wp.receiveEmbedMessage||(d.wp.receiveEmbedMessage=function(e){var t=e.data;if((t||t.secret||t.message||t.value)&&!/[^a-zA-Z0-9]/.test(t.secret)){for(var s,r,n,a=l.querySelectorAll('iframe[data-secret="'+t.secret+'"]'),o=l.querySelectorAll('blockquote[data-secret="'+t.secret+'"]'),c=new RegExp("^https?:$","i"),i=0;i<o.length;i++)o[i].style.display="none";for(i=0;i<a.length;i++)s=a[i],e.source===s.contentWindow&&(s.removeAttribute("style"),"height"===t.message?(1e3<(r=parseInt(t.value,10))?r=1e3:~~r<200&&(r=200),s.height=r):"link"===t.message&&(r=new URL(s.getAttribute("src")),n=new URL(t.value),c.test(n.protocol))&&n.host===r.host&&l.activeElement===s&&(d.top.location.href=t.value))}},d.addEventListener("message",d.wp.receiveEmbedMessage,!1),l.addEventListener("DOMContentLoaded",function(){for(var e,t,s=l.querySelectorAll("iframe.wp-embedded-content"),r=0;r<s.length;r++)(t=(e=s[r]).getAttribute("data-secret"))||(t=Math.random().toString(36).substring(2,12),e.src+="#?secret="+t,e.setAttribute("data-secret",t)),e.contentWindow.postMessage({message:"ready",secret:t},"*")},!1)))}(window,document); //# sourceURL=https://tbenews.com/tbe/wp-includes/js/wp-embed.min.js </script> https://tbenews.com/tbe/wp-content/uploads/2017/07/Sweden.jpg1180250TBE in Sweden Åke Lundkvist E-CDC risk status: endemic (data as of end 2022) History and current situation Tick-borne encephalitis virus (TBEV) was isolated for the first time in Sweden in 1958 (from ticks and from 1 tick-borne encephalitis [TBE] patient).1 In 2003, Haglund and colleagues reported the isolation and antigenic and genetic characterization of 14 TBEV strains from Swedish patients (samples collected 1991–1994).2 The first serum sample, from which TBEV was isolated, was obtained 2–10 days after onset of disease and found to be negative for anti-TBEV immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA), whereas TBEV-specific IgM (and TBEV-specific immunoglobulin G/cerebrospinal fluid [IgG/CSF] activity) was demonstrated in later serum samples taken during the second phase of the disease. Of 20 patient serum samples inoculated into the brain of suckling mice, 14 induced obvious signs of illness (death or clear physical signs in all cases, 5–7 days after inoculation), and TBEV was isolated in all cases. Three earlier Swedish TBEV patient isolates from 1958,1 1959, and 1966, respectively, were included in the same study. Phylogenetic analyses of the partial sequence (domain III) of the E gene revealed that all Swedish TBEV strains grouped together with the previously characterized strains (Neudoerfl, Kumlinge-A52, Hypr, and TBE 263) of the Western or European subtype of TBEV (TBEV-EU). In 2007, a partial TBEV sequence (approximately one-third of the viral genome) from a small pool of ticks collected in the Stockholm archipelago on the island of Torö was reported.3 The sequence was characterized and compared with those of other tick-borne flaviviruses, which led to classification of the virus as TBEV-EU. The same group reported in 2011 on the first complete genome of a Swedish TBEV strain by completing the earlier partial sequencing (see above).4 The total RNA was sufficient for the sequencing of a complete TBEV genome (Torö-2003), without conventional enrichment procedures such as cell culture or amplification in suckling mice. Sequence analyses also revealed that Torö-2003 belonged to the TBEV-EU subtype, being most similar to TBE 263 with 97.4% and 98.8% homologies at the nucleotide and amino acid levels, respectively. In 2014, Veje and coworkers reported 2 cases of TBE in which TBEV RNA could be detected in urine by real-time polymerase chain reaction (PCR) during the encephalitic phase.5 The TBEV RNA quantities from 1 patient allowed sequencing of 10,432 nucleotides (nt), which confirmed the PCR finding in urine, and phylogenetic analysis showed that the virus belonged to the TBEV-EU clade. In 2016, Henningsson and associates reported isolation and a complete TBEV sequence from a biting tick.6 By performing nt sequencing of the virus strain (Tick/SWE/Habo/2011/1) via 2 different strategies (deep sequencing of the A549 isolate and direct sequencing of PCR amplicons of RNA extracted from the tick, respectively), the authors showed that the 2 sequences were identical over 3382 nt, thereby suggesting that the virus isolation procedure did not introduce a selection bias with regard to the compared nt sequences. As in other areas of Europe, the number of reported TBE cases has increased during the last 25 years. The mortality of TBE in Sweden is significant (1.4%)7 and the morbidity and long-term sequelae make it a disease of great importance in the endemic regions.8–10 TBE has been reported in Sweden from diagnostic laboratories on a voluntary basis since the 1970s and notification has been mandatory since 2004. During the years 2007–2019, between 181 and 391 (year 2017) cases of TBE were reported annually in Sweden despite the fact that vaccination has increased in the exposed population. There are 2 TBE vaccines available in Sweden: FSME-Immun (Pfizer) introduced in 1988 and Encepur (Bavarian Nordic) introduced in 2003. Vaccination against TBE is voluntary in Sweden. The vaccination schedule recommended in Sweden follows the recommendations of the manufacturers, with one exception being that after dose 4 and onwards, a 5-year interval is recommended, irrespective of age (the manufacturers recommend 3-year booster intervals after the age of 60). The change to a 5-year interval after dose 4 and onwards was based on a large study of the serological response in 535 persons in Sweden after TBE vaccination.11 However, if TBE vaccination is initiated over age 60, the recommended schedule is 1 extra dose 2 months after the second dose, i.e. the initial vaccination includes 4 doses at 0, 1, 3, and 5-12 months. The number of vaccine doses sold in Sweden has averaged from 500,000 to 600,000 annually since 2006, but increased to 1.2 million doses per year in 2018. Because TBE vaccination is not included in any official vaccination registry, the actual number of immunized individuals is unknown. To estimate the TBE vaccination coverage in the greater Stockholm region, a questionnaire was sent to a randomized sample of 8000 individuals in 2013.12 Fifty-three percent of all respondents reported being vaccinated against TBE at least once. Based on these findings, the estimated TBE incidence in the unvaccinated regional population was 8.5–12/100,000, which is comparable to highly endemic areas in the Baltics and Central Europe. The protection rate of the vaccine has been estimated to be 96% to 98% according to field studies in Austria. In a study from 2010, data from 27 Swedish patients with clinical symptoms and signs of TBE, together with serological evidence of TBEV infection despite active vaccination, was presented.13 These vaccination failures were characterized by a slow and initially non-detectable development of TBEV-specific IgM, seen together with a rapid rise of IgG and neutralizing antibodies in serum. The majority (70%) of the 27 patients were above age 50, which indicated the need for a modified immunization strategy in the elderly (as noted above). Recently, a new tool (TBE suspension multiplex immunoassay, TBEV SMIA) for improved diagnostics of TBEV infections was reported.17 The TBEV SMIA can accurately differentiate TBEV infections from TBE vaccination and further studies have now been initiated to evaluate the efficiency of the assay for diagnosis of potential vaccine failures. Recently, the TBEV SMIA was evaluated using samples from 14 previously confirmed Swedish TBEV vaccine failure patients.18 The