Search

Bourbon virus is a tickborne virus that can cause human disease. Cases have been reported in Kansas, Oklahoma, and Missouri, USA. We identified Bourbon virus-specific neutralizing antibodies in patients from North Carolina. Bourbon virus infections are likely more common than previously thought, highlighting the need for improved diagnostics and surveillance.

A case of Powassan encephalitis occurred in Manitoba, Canada, after the bite of a black-legged tick. Awareness of this emerging tickborne illness is needed because the number of vector tick species is growing. No specific treatment options exist, and cases with illness and death are high. Prevention is crucial.

Tick-borne encephalitis was limited to northeast portions of Italy. We report in Lombardy, a populous region in the northwest, a chamois displaying clinical signs of tickborne encephalitis virus that had multiple virus-positive ticks attached, as well as a symptomatic man. Further, we show serologic evidence of viral circulation in the area.

Tick-borne encephalitis virus (TBEV) is an emerging pathogen that was first detected in ticks and humans in the Netherlands in 2015 (ticks) and 2016 (humans). To learn more about its distribution and prevalence in the Netherlands, we conducted large-scale surveillance in ticks and rodents during August 2018-September 2020. We tested 320 wild rodents and >46,000 ticks from 48 locations considered to be at high risk for TBEV circulation. We found TBEV RNA in 3 rodents (0.9%) and 7 tick pools (minimum infection rate 0.02%) from 5 geographically distinct foci. Phylogenetic analyses indicated that 3 different variants of the TBEV-Eu subtype circulate in the Netherlands, suggesting multiple independent introductions. Combined with recent human cases outside known TBEV hotspots, our data demonstrate that the distribution of TBEV in the Netherlands is more widespread than previously thought.

We assessed standardized mortality ratio in tick-borne encephalitis (TBE) in Sweden, 2004-2017. Standardized mortality ratio for TBE was 3.96 (95% CI 2.55-5.90); no cases in patients <40 years of age were fatal. These results underscore the need for further vaccination efforts in populations at risk for TBE.

Information on febrile illness caused by tick-borne encephalitis virus (TBEV) without central nervous system involvement is limited. We characterized 98 patients who had TBEV RNA in their blood but no central nervous system involvement at the time of evaluation. Median duration of illness was 7 days; 37 (38%) patients were hospitalized. The most frequent findings were malaise or fatigue (98%), fever (97%), headache (86%), and myalgias (54%); common laboratory findings were leukopenia (88%), thrombocytopenia (59%), and abnormal liver test results (63%). During the illness, blood leukocyte counts tended to improve, whereas thrombocytopenia and liver enzymes tended to deteriorate. At the time of positive PCR findings, 0/98 patients had serum IgG TBEV and 7 serum IgM TBEV; all patients later seroconverted. Viral RNA load was higher in patients with more severe illness but did not differ substantially in relation to several other factors. Illness progressed to tick-borne encephalitis in 84% of patients within 18 days after defervescence.

We report 3 confirmed autochthonous tick-borne encephalitis cases in Belgium diagnosed during summer 2020. Clinicians should include this viral infection in the differential diagnosis for patients with etiologically unexplained neurologic manifestations, even for persons without recent travel history.

Tick-borne encephalitis (TBE) is an endemic infection of public health importance in Finland. We investigated the effect of ecologic factors on 2007-2017 TBE trends. We obtained domestic TBE case data from the National Infectious Diseases Register, weather data from the US National Oceanic and Atmospheric Administration, and data from the Natural Resources Institute in Finland on mammals killed by hunters yearly in game management areas. We performed a mixed-effects time-series analysis with time lags on weather and animal parameters, adding a random effect to game management areas. During 2007-2017, a total of 395/460 (86%) domestic TBE cases were reported with known place of exposure and date of sampling. Overall, TBE incidence increased yearly by 15%. After adjusting for the density of other animals and minimum temperatures, we found thatTBE incidence was positively associated with white-tailed deer density. Variation in host animal density should be considered when assessing TBE risks and designing interventions.

During February 2018-January 2019, we conducted large-scale surveillance for the presence and prevalence of tick-borne encephalitis virus (TBEV) and louping ill virus (LIV) in sentinel animals and ticks in the United Kingdom. Serum was collected from 1,309 deer culled across England and Scotland. Overall, 4% of samples were ELISA-positive for the TBEV serocomplex. A focus in the Thetford Forest area had the highest proportion (47.7%) of seropositive samples. Ticks collected from culled deer within seropositive regions were tested for viral RNA; 5 of 2,041 ticks tested positive by LIV/TBEV real-time reverse transcription PCR, all from within the Thetford Forest area. From 1 tick, we identified a full-length genomic sequence of TBEV. Thus, using deer as sentinels revealed a potential TBEV focus in the United Kingdom. This detection of TBEV genomic sequence in UK ticks has important public health implications, especially for undiagnosed encephalitis.

Three autochthonous cases of tick-borne encephalitis (TBE) acquired in rural areas of France where Lyme borreliosis, but not TBE, is endemic highlight the emergence of TBE in new areas. For patients with neurologic involvement who have been in regions where Ixodes ticks circulate, clinicians should test for TBE virus and other tickborne viruses.

Using long-term data on incidences of Lyme disease and tickborne encephalitis, we showed that the dynamics of both diseases in central Europe are predictable from rodent host densities and climate indices. Our approach offers a simple and effective tool to predict a tickborne disease risk 1 year in advance.

Evidence of spinal cord involvement in Powassan virus infection is largely limited to mouse models. We report a case of a polio-like illness caused by Powassan virus infection in a 62-year-old man in Canada. Magnetic resonance imaging showed T2 hyperintensities in the anterior horns of the cervical spinal cord.

We determined levels of tick-borne encephalitis (TBE) virus (TBEV) RNA in serum samples obtained from 80 patients during the initial phase of TBE in Slovenia. For most samples, levels were within the range of 3-6 log 10 copies RNA/mL. Levels were higher in female patients than in male patients, but we found no association between virus load and several laboratory and clinical parameters, including severity of TBE. However, a weak humoral immune response was associated with a more severe disease course, suggesting that inefficient clearance of virus results in a more serious illness. To determine whether a certain genetic lineage of TBEV had a higher virulence potential, we obtained 56 partial envelope protein gene sequences by directly sequencing reverse transcription PCR products from clinical samples of patients. This method provided a large set of patient-derived TBEV sequences. We observed no association between phylogenetic clades and virus load or disease severity.

Little is known about the occurrence of tick-borne encephalitis in Romania. Sheep are an infection source for humans and are useful sentinels for risk analysis. We demonstrate high antibody prevalence (15.02%) among sheep used as sentinels for this disease in 80% of the tested localities in 5 counties of northwestern Romania.

During early 2017, we conducted a seroepidemiologic investigation for tickborne encephalitis virus among 291 Japan Self-Defense Forces members in Hokkaido. Two (0.7%) tested positive. Neither had clinically apparent symptoms after removing ticks.

Powassan virus (POWV) lineage II is an emerging tickborne flavivirus with an unknown seroprevalence in humans. In a Lyme disease-endemic area, we examined the seroreactivity to POWV in 2 patient cohorts and described the clinical features of the POWV-seroreactive patients. POWV disease might be less neuroinvasive than previously thought.

We report the presence of tick-borne encephalitis virus (TBEV) in the Netherlands. Serologic screening of roe deer found TBEV-neutralizing antibodies with a seroprevalence of 2%, and TBEV RNA was detected in 2 ticks from the same location. Enhanced surveillance and awareness among medical professionals has led to the identification of autochthonous cases.

During 2006-2014, four tick-borne encephalitis (TBE) cases occurred among Israeli travelers. We calculated TBE incidence at 321.0, 45.0, 13.2, and 7.5 cases/100,000 travelers/year of travel to Sweden, Switzerland, Austria, and Germany, respectively. TBE incidence among travelers to these destinations appears to justify TBE vaccination in accordance with World Health Organization recommendations.

Powassan virus, a member of the tick-borne encephalitis group of flaviviruses, encompasses 2 lineages with separate enzootic cycles. The prototype lineage of Powassan virus (POWV) is principally maintained between Ixodes cookei ticks and the groundhog (Marmota momax) or striped skunk (Mephitis mephitis), whereas the deer tick virus (DTV) lineage is believed to be maintained between Ixodes scapularis ticks and the white-footed mouse (Peromyscus leucopus). We report 14 cases of Powassan encephalitis from New York during 2004-2012. Ten (72%) of the patients were residents of the Lower Hudson Valley, a Lyme disease-endemic area in which I. scapularis ticks account for most human tick bites. This finding suggests that many of these cases were caused by DTV rather than POWV. In 2 patients, DTV infection was confirmed by genetic sequencing. As molecular testing becomes increasingly available, more cases of Powassan encephalitis may be determined to be attributable to the DTV lineage.

Powassan virus is endemic to the United States, Canada, and the Russian Far East. We report serologic evidence of circulation of this virus in Alaska, New Mexico, and Siberia. These data support further studies of viral ecology in rapidly changing Arctic environments.

Tick-borne encephalitis (TBE) developed in 3 persons in Slovenia who drank raw milk; a fourth person, who had been vaccinated against TBE, remained healthy. TBE virus RNA was detected in serum and milk of the source goat. Persons in TBE-endemic areas should be encouraged to drink only boiled/pasteurized milk and to be vaccinated.

An unexpectedly high infection rate (26.1%) of tick-borne encephalitis virus (TBEV) was identified in a herd of 257 horses of the same breed distributed among 3 federal states in Austria. Young age (p<0.001) and male sex (p=0.001) were positively associated with infection.

Tick-borne encephalitis (TBE) is a substantial public health problem in many parts of Europe and Asia. To assess the effect of increasing TBE vaccination coverage in Austria, we compared incidence rates over 40 years for highly TBE-endemic countries of central Europe (Czech Republic, Slovenia, and Austria). For all 3 countries we found extensive annual and longer range fluctuations and shifts in distribution of patient ages, suggesting major variations in the complex interplay of factors influencing risk for exposure to TBE virus. The most distinctive effect was found for Austria, where mass vaccination decreased incidence to ≈16% of that of the prevaccination era. Incidence rates remained high for the nonvaccinated population. The vaccine was effective for persons in all age groups. During 2000-2011 in Austria, ≈4,000 cases of TBE were prevented by vaccination.

Tick-borne encephalitis virus (TBEV) is an emerging pathogen in Europe and Asia. We investigated TBEV in Kyrgyzstan by collecting small mammals and ticks from diverse localities and analyzing them for evidence of TBEV infection. We found TBEV circulating in Kyrgyzstan much farther south and at higher altitudes than previously reported.

Rodents might maintain tick-borne encephalitis virus (TBEV) in nature through latent persistent infections. During 2 subsequent winters, 2008 and 2009, in Finland, we detected RNA of European and Siberian subtypes of TBEV in Microtus agrestis and Myodes glareolus voles, respectively. Persistence in rodent reservoirs may contribute to virus overwintering.

Alkhurma virus is a flavivirus, discovered in 1994 in a person who died of hemorrhagic fever after slaughtering a sheep from the city of Alkhurma, Saudi Arabia. Since then, several cases of Alkhurma hemorrhagic fever (ALKHF), with fatality rates up to 25%, have been documented. From January 1, 2006, through April 1, 2009, active disease surveillance and serologic testing of household contacts identified ALKHF in 28 persons in Najran, Saudi Arabia. For epidemiologic comparison, serologic testing of household and neighborhood controls identified 65 serologically negative persons. Among ALKHF patients, 11 were hospitalized and 17 had subclinical infection. Univariate analysis indicated that the following were associated with Alkhurma virus infection: contact with domestic animals, feeding and slaughtering animals, handling raw meat products, drinking unpasteurized milk, and being bitten by a tick. After multivariate modeling, the following associations remained significant: animal contact, neighboring farms, and tick bites.

Increased tick-borne encephalitis (TBE) cases have been reported in central Europe. To investigate temporal trends in the altitude at which TBE cases occur in Slovakia, we analyzed the number of TBE cases during 1961-2004. Since 1980, TBE cases moved from lowlands to submountainous areas, most likely because of rising temperature.

We report transmission of tick-borne encephalitis virus (TBEV) in July 2008 through nonpasteurized goat milk to 6 humans and 4 domestic pigs in an alpine pasture 1,500 m above sea level. This outbreak indicates the emergence of ticks and TBEV at increasing altitudes in central Europe and the efficiency of oral transmission of TBEV.

We recently determined that Nanjianyin virus, isolated from serum of a patient in Yunnan Province, China, in 1989, is a type of Kyasanur Forest disease virus. Results of a 1987-1990 seroepidemiologic investigation in Yunnan Province had shown that residents of the Hengduan Mountain region had been infected with Nanjianyin virus.

A strain of Greek goat encephaltitis virus was isolated from engorged Ixodes ricinus ticks that had fed on goats in northern Greece. The strain was almost identical to the prototype strain isolated 35 years ago.

We isolated a novel strain of tickborne encephalitis virus (TBEV), Glubinnoe/2004, from a patient with a fatal case in Russia. We sequenced the strain, whose landmark features included 57 amino acid substitutions and 5 modified cleavage sites. Phylogenetically, Glubinnoe/2004 is a novel variant that belongs to the Eastern type of TBEV.

During spring and autumn 2001, we screened 13,260 migrating birds at Ottenby Bird Observatory, Sweden, and found 3.4% were infested with ticks. Four birds, each a different passerine species, carried tickborne encephalitis virus (TBEV)-infected ticks (Ixodes ricinus). Migrating birds may play a role in the geographic dispersal of TBEV-infected ticks.

We report an autochthonous human case of tickborne encephalitis (TBE) in the Bordeaux area, southwestern France. The patient was a farmer who had severe encephalomyelitis. ELISA and neutralization assay of serum and cerebrospinal fluid established the diagnosis. This potential new endemic focus for TBE virus should be further investigated.

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.

Serum from 2 Norwegians with tickborne encephalitis (TBE) (1 of whom was infected in Denmark) and 810 Norwegian ticks were tested for TBE virus (TBEV) RNA by reverse transcription-polymerase chain reaction. Sequencing and phylogenetic analysis were performed. This is the first genome detection of TBEV in serum from Norwegian patients.

We conducted a study of the distribution and prevalence of tickborne infections in Denmark by using roe deer as sentinels. Blood samples from 237 roe deer were collected during the 2002-2003 hunting season. Overall, 36.6% of deer were Borrelia seropositive, while 95.6% were Anaplasma phagocytophilum positive; all animals were negative for Bartonella quintana and B. henselae by indirect immunofluorescence assay. When a hemagglutination-inhibition test was used, 8.7% of deer were found positive for tickborne encephalitis (TBE)-complex virus. A total of 42.6% were found positive by polymerase chain reaction (PCR) for A. phagocytophilum with significant seasonal variation. All were PCR negative for Rickettsia helvetica. PCR and sequencing also showed a novel bacterium in roe deer previously only found in ticks. The study showed that the emerging pathogen A. phagocytophilum is widely distributed and that a marked shift has occurred in the distribution of TBE-complex virus in Denmark. This finding supports studies that predict alterations in distribution due to climatic changes.

The first reported case of tickborne encephalitis (TBE) in Norway occurred in 1997. From 1997 to 2003, from zero to two cases of human TBE have been diagnosed per year in Norway, for a total of eight cases. Clinical TBE cases in dogs are not reported in Norway.

The first five cases of human tick-borne encephalitis in Norway were reported from Tromöya, in Aust-Agder County. Serum specimens from 317 dogs in the same geographic area were collected. An enzyme immunoassay demonstrated antibody to human tick-borne encephalitis virus in 52 (16.4%) of the dogs, which supports the notion of an emerging disease.

Eight fatal cases of tick-borne encephalitis with an unusual hemorrhagic syndrome were identified in 1999 in the Novosibirsk Region, Russia. To study these strains, we sequenced cDNA fragments of protein E gene from six archival formalin-fixed brain samples. Phylogenetic analysis showed tick-borne encephalitis variants clustered with a Far Eastern subtype (homology 94.7%) but not with the Siberian subtype (82%).

We assessed the risk for human tick-borne encephalitis (TBE), ixodid tick-borne borrelioses, and double infection from 1994 to 1998 in Perm, which has among the highest rates of reported cases in Russia. We studied 3,473 unfed adult Ixodes persulcatus ticks collected from vegetation in natural foci and 62,816 ticks removed from humans. TBE virus and Borrelia may coexist in ticks.

Although Japanese encephalitis has declined as an important cause of illness and death in Japan, infection with other flaviviruses has become a public health concern. Recently, reports of imported dengue cases, as well as isolations of tick-borne encephalitis virus, have increased.