{"version":"1.0","provider_name":"TBE Book","provider_url":"https:\/\/tbenews.com\/tbe","author_name":"logesan","author_url":"https:\/\/tbenews.com\/tbe\/author\/logesan\/","title":"Norway - TBE Book","type":"rich","width":600,"height":338,"html":"<blockquote class=\"wp-embedded-content\" data-secret=\"wSN0NseFvN\"><a href=\"https:\/\/tbenews.com\/tbe\/13-24-9\/\">Norway<\/a><\/blockquote><iframe sandbox=\"allow-scripts\" security=\"restricted\" src=\"https:\/\/tbenews.com\/tbe\/13-24-9\/embed\/#?secret=wSN0NseFvN\" width=\"600\" height=\"338\" title=\"&#8220;Norway&#8221; &#8212; TBE Book\" data-secret=\"wSN0NseFvN\" frameborder=\"0\" marginwidth=\"0\" marginheight=\"0\" scrolling=\"no\" class=\"wp-embedded-content\"><\/iframe><script>\n\/*! This file is auto-generated *\/\n!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);\n\/\/# sourceURL=https:\/\/tbenews.com\/tbe\/wp-includes\/js\/wp-embed.min.js\n<\/script>\n","thumbnail_url":"https:\/\/tbenews.com\/tbe\/wp-content\/uploads\/2017\/07\/Norway.jpg","thumbnail_width":1180,"thumbnail_height":250,"description":"TBE in Norway \u00c5shild K. Andreassen, Andrea P. Cotes-Perdomo, Arnulf Soleng,Urusha Maharjan, Heidi H. Lindstedt, Kristian Alfsnes, and Rikard Rykkvin (last edited in June 2026, update for 2024: 78 reported cases; update for 2025: 97 reported cases) History and current situation In Norway, tick-borne encephalitis (TBE) has been a mandatory notifiable disease since 1975 (Norwegian Surveillance System for Communicable Diseases, MSIS).1 According to ECDC&#8217;s classification, coastal areas in southern Norway (counties of Agder, Vestfold and Telemark) are endemic for TBE. Further, the counties of \u00d8stfold, Akershus, and Buskerud, and western and northern Norway to Br\u00f8nn\u00f8y municipality are imperiled.2-12 The first reported case of TBE occurred in 1997 at Trom\u00f8y in Agder County.13 This is a region with holiday cabins and outdoor recreation areas for both local inhabitants and tourists, and it is known for high temperatures during spring and summer. In addition, TBE antibodies in dogs and tick-borne encephalitis virus (TBEV) in ticks have been detected in this area.10,12-15 A total number of TBE cases have been reported to MSIS as of February 2025 (Fig. 1). Of these, the majority are autochthonous infections, while the remainder were infected abroad or have an unknown infection history. The number of cases varies annually between 1 and 97 (Table 1 and Fig. 1). Data from 2018 to 2025 show an increase in the number of reported cases, especially in the counties of Vestfold and Telemark (Fig. 5). In 2023, the first case from Vestland County was reported to MSIS. The TBE patients\u2019 age distribution is in accordance with other European studies, with a higher infection rate among those older than 30 years (Table 2 and Fig. 2).16\u201317 According to MSIS, the reported cases in Norway are represented mainly by the counties of Agder, Vestfold and Telemark, and Viken, all located in the southern part of the country (Fig. 3). No cases are reported from the northern coastal areas, although a few cases are reported from the western areas and the area east of the Oslofjord, despite outdoor recreational activities being common throughout the country. Ticks and TBEV in Norway The castor bean tick (Ixodes ricinus) is the most common tick species in Europe,18 and considered to be the major vector of the European TBE-virus.19-20 The geographical distribution of I. ricinus in Norway has been investigated in several studies.2-4,10,21-25 Both Tambs-Lyche (1943) and Mehl (1983) found I. ricinus to be mainly distributed in the coastal areas of Norway, from the southeastern border to Sweden, along the southern and western coastline, up to Nordland County at ~65.1\u00b0N.2,3,21-25 The density of ticks varies between locations, even when separated by short distances. This is probably caused by differences in microclimatic conditions, vegetation, and density of vertebrate hosts. However, locations with a high density of ticks are found all over the major distributional range. The density of ticks declines rapidly with both increasing distance from the coast and increasing altitude. In a multi-source study, Jore et al. (2011) suggested that tick populations in Norway had undergone recent shifts in latitudinal and altitudinal range.7 This result is, however, disputed in recent studies.4,5 Although ticks are reported far outside (i.e. northeast) of the hitherto established distribution limit of I. ricinus in Norway, the vast majority of these are engorged females.24-26 Migratory birds may deposit engorged larvae or nymphs in areas where temperatures permit development to the next stage but not completion of the life cycle. Thus, such records do not constitute evidence for established and sustainable tick populations as this requires the presence of all the active stages (larvae, nymphs, and adults) in a locality for at least two consecutive seasons.27,28 Using flagging and dragging, Soleng et al. (2018) found tick larvae, nymphs and adults to be abundant at 64.5 and 65.1\u00b0N. Only a few tick nymphs and adults, and no larvae, were found at locations close to 66\u00b0N. At several locations from 66.3\u00b0N up to 67.5\u00b0N no ticks were found.3 In a recent study by Hvidsten et al. (2020), the occurrence of ticks in northern Norway was examined by dragging in 109 separate locations between the latitudes of 64\u00b0N and 70\u00b0N. The northernmost location with a permanent I. ricinus population was at 66.2\u00b0N on the Island of D\u00f8nna (Fig. 4).5,6 It is noteworthy that the taiga tick (Ixodes persulcatus) and the meadow tick (Dermacentor reticulatus) were not detected in a large screening of ticks collected in the southern part of Norway in 2016.29 Studies of I. ricinus in Norway have detected TBEV in nymphs with a prevalence ranging from 0% to 1.1%. In adult ticks collected from the same areas, the prevalence ranges from 0% to 20.6%. TBEV positive ticks have been found in sampling areas along the Norwegian coastline from the east of \u00d8stfold County to Br\u00f8nn\u00f8y in Nordland County.12 The highest estimated TBEV prevalence in adult ticks has been found in the counties of Rogaland and Vestfold and Telemark. In nymphs, the highest prevalence has been found in Vestfold, Telemark, Agder, and Rogaland. 12 Historically, the first suggested TBEV isolate from Norway was collected in I. ricinus from Vestland County (former Sogn and Fjordane) in June 1976, as described by Traavik and co-workers. Five virus strains with a close serological relationship to the TBEV complex were detected in this study.25 One pool of ten nymphs collected from southern Norway has been whole-genome sequenced and phylogenetically characterized. This strain, \u201cMandal 2009\u201d, was found to belong to the Scandinavian group of the European TBEV subtype. Interestingly, \u201cMandal 2009\u201d revealed a shorter form of the TBEV genome within the 3\u2019 non-coding region, like the highly virulent \u201cHypr\u201d strain.20 Recent unpublished findings indicate the circulation of at least one new TBEV variant in Norway from two new areas. This variant in the TBEV sequence is detected in a tick and one patient sample, both different from the previous Mandal 2009 strain.31,32 Seroprevalence in animals In addition to tick studies, a seroprevalence study has detected TBE antibodies in specimens from cervids (deer) collected in Farsund (Agder County) and Molde (M\u00f8re and"}