Febre do Nilo Ocidental / West Nile fever

A Febre do Nilo Ocidental (FNO) é uma infecção viral transmitida por meio da picada de mosquitos, principalmente do gênero Culex (pernilongo) infectados pelo agente etiológico, cujos hospedeiros naturais são algumas espécies de aves silvestres, que atuam como amplificadoras do vírus e como fonte de infecção para os vetores. Tal doença pode também infectar humanos, equinos, primatas e outros mamíferos sendo que, homem e equídeos são considerados hospedeiros acidentais e terminais, uma vez que a contaminação pelo vírus se dá por um curto período de tempo e em níveis insuficientes para infectar mosquitos, encerrando o ciclo de transmissão (WHO, 2017; ECDC , 2022a; CDC, 2017; BRASIL, 2021)

West Nile Fever (WNF) is a viral infection transmitted through the bite of mosquitoes, mainly of the Culex genus (legged mosquito) infected by the etiological agent, whose natural hosts are some species of wild birds, which act as amplifiers of the virus and as source of infection for the vectors. Such a disease can also infect humans, horses, primates and other mammals, and humans and horses are considered accidental and terminal hosts, since contamination by the virus occurs for a short period of time and at levels insufficient to infect mosquitoes, ending the transmission cycle (WHO, 2017; ECDC, 2022a; CDC, 2017). ; BRAZIL, 2021)

Evidence for current circulation of an ancient West Nile virus strain (NY99) in Brazil

Abstract INTRODUCTION: In Brazil, West Nile virus (WNV) was first detected, in 2018, in horses with neurological disease. AIM: We report the first case of WNV infection in a horse from Ceará state and the complete genome sequence of an isolate from Espírito Santo state. Both infections occurred in 2019. METHODS: WNV was isolated from the tissues of a horse with neurological signs in Espírito Santo and sequenced by MiSeq. RESULTS: Phylogenetic analysis revealed that the isolate belongs to lineage 1a, clustering with the NY99 strain, a strain that has not circulated in the USA since 2005. CONCLUSIONS: Our findings reinforce the hypothesis that WNV has been silently circulating in Brazil for many years.

Diagnostic significance of immunoglobulin G avidity in symptomatic and asymptomatic West Nile virus infection

Abstract INTRODUCTION West Nile virus (WNV) immunoglobulin M (IgM) antibodies have been shown to persist for up to 500 days in certain patients. To evaluate the usefulness of immunoglobulin G (IgG) avidity assessment in the diagnosis of WNV infection, we analyzed 54 WNV IgM- and/or IgG-positive serum samples from 39 patients with neuroinvasive disease and 15 asymptomatic cases tested during a seroprevalence investigation. METHODS Serological tests (WNV IgM/IgG antibody detection, IgG avidity) were performed using commercially available enzyme-linked immunosorbent assays. RESULTS WNV IgM antibodies were detected in 47 (87%) samples. Acute/recent WNV infection was confirmed based on low/borderline avidity index (AI) in 44 IgM-positive samples (93.6%). In three IgM-positive samples (6.4%), high IgG AIs were detected, thus indicating persisting IgM antibodies from previous infections. All IgM-negative samples showed high AIs. Patients with WNV neuroinvasive disease tested within 30 days showed low AIs. In six patients tested 34-50 days after disease onset, AI was borderline (42%-60%), suggesting earlier WNV IgG maturation. Samples with the highest IgM values were associated with the lowest AIs (Spearman's rho coefficient -0.767, p < 0.001). CONCLUSIONS Our results indicate that IgG avidity differentiates current/recent WNV infection from persistent IgM seropositivity from the previous WNV transmission season both in patients with WNV neuroinvasive disease and in asymptomatic persons. A strong negative correlation between IgM antibody levels and AI indicates that in cases with very high IgM levels, determination of IgG avidity may not be necessary. As many patients showed rapid avidity maturation, low IgG avidity is indicative of WNV infection within the previous month.

Aspectos clínicos de la infección en seres humanos por el Virus del Nilo Occidental / Clinical Features of West Nile Virus Infection in Humans

ResumenLa infección por el Virus del Nilo Occidental es endémica en Norteamérica desde 1999 y actualmente hay casos aislados en gran parte de América. Aunque el 80 % de los casos son asintomáticos, existe casi un 20 % que se presenta como una enfermedad febril aguda indistinguible de otras infecciones por flavivirus como el Dengue, y menos de 1 % se puede manifestar como un síndrome neurológico grave: meningitis, encefalitis o parálisis flácida; siendo esta la forma más severa y discapacitante de la enfermedad.El diagnóstico debe basarse en un alto índice de sospecha clínico y confirmarse por métodos de laboratorio que usualmente consisten en serología. No existe tratamiento específico, se debe dar manejo de soporte, y algunos autores recomiendan en las formas graves utilizar gammaglobulina. En Costa Rica se han presentado casos de la enfermedad en el año 2010, lo cual sin duda obedece a que se tienen todas las condiciones ambientales para que ocurran, por lo que se sugiere un abordaje multidisciplinario de esta infección.

AbstractThe West Nile Virus infection is endemic in North America since 1999, and nowadays sporadic cases are seen across America. Although 80 % cases are asymptomatic, the remaining 20 % appear as acute febrile illness like other flavivirus infections such as dengue, and less than 1 % may occur as a severe neurologic disease: meningitis, encephalitis or flaccid paralysis; the last being the most severe and disabling form of the disease.The diagnosis should be made when a high index of clinical suspicion is present and confirmed with laboratory tests, such as serology. There is no specific treatment, only support care; and some authors recommend that in severe cases gammaglobulin be used. In Costa Rica there were isolated cases in 2010, which occurred because all necessary environmental conditions were present; therefore a multidisciplinary approach is needed in the management of this infection.

The First Reported Case of West Nile Encephalitis in Korea

West Nile encephalitis was first identified in 1937, but until now, it was never diagnosed in Korea. A 58-yr-old Korean man was admitted with headache and cognitive dysfunction. The patient had been on a business trip in Guinea. Cerebrospinal fluid (CSF) showed pleocytosis. The patient complained of both leg weakness,and arachnoiditis and myelitis were observed on lumbar magnetic resonance imaging (MRI). A specific neutralizing antibody for West Nile virus was positive in serum. After a treatment with interferon-alpha 3mu, follow up CSF findings recovered completely after 3 months later. The first case of West Nile encephalitis in Korea was imported from Guinea, and was cured successfully.

The First Reported Case of West Nile Encephalitis in Korea

West Nile encephalitis was first identified in 1937, but until now, it was never diagnosed in Korea. A 58-yr-old Korean man was admitted with headache and cognitive dysfunction. The patient had been on a business trip in Guinea. Cerebrospinal fluid (CSF) showed pleocytosis. The patient complained of both leg weakness,and arachnoiditis and myelitis were observed on lumbar magnetic resonance imaging (MRI). A specific neutralizing antibody for West Nile virus was positive in serum. After a treatment with interferon-alpha 3mu, follow up CSF findings recovered completely after 3 months later. The first case of West Nile encephalitis in Korea was imported from Guinea, and was cured successfully.

Serological detection of West Nile virus in horses and chicken from Pantanal, Brazil

In an effort to detect West Nile virus (WNV) in Brazil, we sampled serum from horses and chickens from the Pantanal region of the state of Mato Grosso and tested for flavivirus-reactive antibodies by blocking ELISA. The positive samples were further confirmed for serological evidence of WNV infection in three (8%) of the 38 horses and one (3.2%) of the 31 chickens using an 80% plaque-reduction neutralisation test (PRNT80). These results provide evidence of the circulation of WNV in chickens and horses in Pantanal.

Serological detection of St. Louis encephalitis virus and West Nile virus in equines from Santa Fe, Argentina

St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) present ecological and antigenic similarities and are responsible for serious human diseases. In addition, WNV is a significant pathogen in terms of equine health. The purpose of our study was to analyse the seroprevalence of SLEV and WNV in equine sera collected in Santa Fe Province, Argentina. The seroprevalence determined using the plaque reduction neutralisation test was 12.2% for SLEV, 16.2% for WNV and 48.6% for a combination of both viruses. These results provide evidence of the co-circulation of SLEV and WNV in equines in Santa Fe.

Estudio serológico en localidades cubanas con infecciones confirmadas al virus del Nilo Occidental / Serological study carried out in Cuban localities where confirmed Western Nile virus infection is present

Introducción: las primeras infecciones por el virus del Nilo Occidental en Cuba se reportaron en 2004. Objetivo: monitorear y conocer la prevalencia del virus del Nilo Occidental en áreas con casos confirmados de este. Métodos: el estudio se llevó a cabo en la municipalidad de Jatibonico y en la ciudad de Sancti Spiritus. Un total de 14 personas, 8 caballos y 41 aves se estudiaron para la detección de anticuerpos a flavivirus y específicos al virus del Nilo Occidental. Resultados: se confirmó la presencia de anticuerpos específicos a virus del Nilo Occidental en 4 muestras de suero de aves y 4 de caballos. Una persona se confirmó como 1 caso de infección por virus del Nilo Occidental asintomático. Conclusiones: la presencia de anticuerpos específicos al virus del Nilo Occidental en aves residentes, caballos y humanos en áreas con casos confirmados demuestran el establecimiento de un ciclo de amplificación local establecido en Cuba antes de este estudio.

Introduction: First infected cases caused by West Nile virus were reported in Cuba in 2004. Objective: to monitor and learn about the prevalence of the West Nile virus in those areas with confirmed cases. Methods: the study was conducted in Jatibonico municipality and in the city of Sancti Spiritus. A total number of 14 persons, 8 horses and 41 birds were researched to detect antibodies to flavivirus and specific antibodies to West Nile virus. Results: the presence of specific antibodies to West Nile virus was confirmed in 4 samples of sera from birds and in 4 from horses. One person was confirmed as one case of asymptomatic West Nile virus infection. Conclusions: the presence of specific antibodies to West Nile virus in birds, horses and persons residing in areas where there are confirmed cases showed that a local amplification cycle had been established in Cuba before this study.

Seroconversion for west Nile and St. Louis encephalitis viruses among sentinel horses in Colombia

We prospectively sampled flavivirus-naïve horses in northern Colombia to detect West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) seroconversion events, which would indicate the current circulation of these viruses. Overall, 331 (34.1 percent) of the 971 horses screened were positive for past infection with flaviviruses upon initial sampling in July 2006. During the 12-month study from July 2006-June 2007, 33 WNV seroconversions and 14 SLEV seroconversions were detected, most of which occurred in the department of Bolivar. The seroconversion rates of horses in Bolivar for the period of March-June 2007 reached 12.4 percent for WNV and 6.7 percent for SLEV. These results comprise the first serologic evidence of SLEV circulation in Colombia. None of the horses sampled developed symptoms of encephalitis within three years of initial sampling. Using seroconversions in sentinel horses, we demonstrated an active circulation of WNV and SLEV in northern Colombia, particularly in the department of Bolivar. The absence of WNV-attributed equine or human disease in Colombia and elsewhere in the Caribbean Basin remains a topic of debate and speculation.

Is West Nile virus a potential cause of central nervous system infection in Brazil? / Seria o vírus do Oeste do Nilo causa potencial de infecção no sistema nervoso central no Brasil?

Meningitis and encephalitis are complications of West Nile virus (WNV) infection. Although WNV is endemic in North America, the virus has recently been reported in Colombia and Argentina. Investigation of WNV in Brazil is important since this virus has never been studied previously in this country. OBJECTIVE: To investigate the presence of WNV infection in viral encephalitis/meningitis cases of unknown etiology in the city of Rio de Janeiro, Brazil. METHOD: Thirty-seven adults with viral meningitis/encephalitis had their serum and CSF tested for WNV antibodies using the ELISA method. RESULTS: Only one case was WNV-positive, but this case was also positive for dengue. The plaque reduction neutralization test distinguished infections, and was negative for WNV. CONCLUSION: WNV can be confused with dengue infection. Their symptoms and neurological picture are similar. We did not find WNV in any patients with encephalitis and meningitis in the city of Rio de Janeiro. Up to now, it has not been detected in Brazil.

Meningite e encefalite são complicações da infecção pelo vírus do Oeste do Nilo (VON). Embora o VON seja endêmico na América do Norte, recentemente o vírus foi descrito na Colômbia e Argentina. Sua pesquisa no Brasil é importante uma vez que o vírus nunca fora estudado antes em nosso país. OBJETIVO: Investigar a presença do VON em casos de meningite e encefalite viral de etiologia desconhecida, na cidade no Rio de Janeiro, Brasil. MéTODO: Trinta e sete adultos com quadro de meningite/encefalite tiveram seu LCR e soro testados para anticorpos anti-VON, pelo método ELISA. RESULTADOS: Apenas um caso obteve sorologia positiva para VON, mas a sorologia para dengue também fora positiva. O teste da neutralização por redução de placa foi utilizado para distinção entre as infecções, sendo negativo para VON. CONCLUSÃO: A infecção por VON pode ser confundida com a infecção pelo vírus da dengue, seus sintomas e quadro neurológico são similares. Nós não encontramos o VON em pacientes com meningite/ encefalite na cidade do Rio de Janeiro. Até o momento ele ainda não foi identificado no Brasil.

El virus del Oeste del Nilo: una realidad en México / West Nile virus: a reality in Mexico

El virus del Oeste del Nilo (VON) es un virus ARN perteneciente a la familia Flaviviridae del género Flavivirus que causa infección en aves, equinos y humanos. La infección por VON es transmitida por el mosquito Culex sp. El ciclo de vida del virus incluye a los mosquitos como vectores y a las aves como huéspedes naturales. El virus mantiene un ciclo de transmisión mosquito–ave-mosquito. Los seres humanos son huéspedes accidentales. Se han reportado epidemias en Rumania, Nueva York e Israel. Mediante el programa de vigilancia epidemiológica en nuestro país, se han reportado 90 muestras positivas en 1,223 casos estudiados en aves hasta el 15 de Septiembre del 2005. La enfermedad por el VON se presenta con fiebre, malestar general, anorexia, nausea, vómito, cefalea, mialgia, erupción cutánea y linfadenopatía. La principal entidad clínica descrita es la encefalitis y la parálisis flácida. A mayor edad, es mayor el riesgo de enfermedad neurológica y muerte. Los métodos diagnósticos incluyen determinación de anticuerpos IgM e IgG en suero y/o liquido cerebroespinal. No existe tratamiento antiviral para la infección por VON. Algunas terapias que se han utilizado incluyen interferón α2b e inmunoglobulina específica contra VON. La prevención juega un papel crucial.

West Nile virus (WNV) is a RNA virus of the Flaviridae, genus flavivirus family. It is a neuropathogenic virus causing disease in birds, horses and humans. WNVis transmitted by the vector mosquito Culex sp. The virus life 's cycle includes mosquitoes as vectors and birds as natural hosts. Humans are accidental hosts. Since the introduction of the Epidemiological Surveillance Program at the Ministry ofHealth. we have documented 90 positive test results among birds out of 1,223 cases studied in Mexico as of September IS. 2005. The incubation period in humans after a mosquito bite ranges from 3 to 14 days. Disease is characterized by early onset fever, general malaise, decreased appetite, nausea, vomiting, headaches, myalgias, enlarged lymph nodes andrash. Neurological manifestations include encephalitis andflaccid paralysis, which are present in less than 1% of subjects infected with WNV. Older patients display more adverse outcomes including death. The diagnosis is made by the determination of specific IgM and JgG antibodies in serum and/or cerebrospinal fluid. There is no antiviral treatment to date against WNV but interferon ?2b, and WNVspec4ic-immunoglobulin have been used Prevention is therefore the key to control the infection.

Virus del oeste del Nilo: ecología y epidemiología de un patógeno emergente en Colombia / West Nile virus; ecology and epidemiology of an emerging pathogen in Colombia

El virus del oeste del Nilo (VON) es mantenido en la naturaleza en un ciclo enzoótico ave-mosquito-ave. Los principales vectores son los mosquitos del genero Culex. Las aves son los huéspedes amplificadores primarios. Humanos y caballos son huéspedes incidentales finales. En humanos las infecciones por VON se presentan como enfermedad febril autolimitada. En los casos de enfermedad neurológica se puede presentar encefalitis, meningitis o meningoencefalitis, con mayor incidencia y mortalidad por encefalitis en personas de mayor edad y pacientes inmunocomprometidos. Se han reportado brotes en Africa, Medio Oriente, Europa y Asia. El virus apareció por primera vez en Estados Unidos en 1999 y se ha documentado su circulación en México, Islas Caimán, Jamaica, Republica Dominicana, Martinica, Guadalupe, Cuba, Puerto Rico, El Salvador y recientemente Colombia. La importancia en salud pública de VON si es introducido en áreas de Centro y Sur América dependerá del resultado de la interacción de múltiples factores. Colombia reúne las condiciones que favorecen su entrada y desarrollo. Se pueden postular dos hipótesis: el virus podría llegar a ser enzoótico y endémico y causar limitada enfermedad humana, o podría llegar a ser epidémico y causar brotes anuales que afecten humanos y animales. Esto dependerá de la susceptibilidad de las especies aviares colombianas al virus por las diferencias en su biología, y a las variaciones geográficas intraespecificas en la competencia de las diferentes especies de mosquito y los efectos de las condiciones medioambientales sobre su habilidad para transmitir el virus, y estos factores son determinantes en el ciclo de amplificación primario.

Effect of bird-to-bird transmission of the West Nile virus on the dynamics of the transmission of this disease.

Two recent publications report that direct bird-to-bird transmission of West Nile virus is possible. The effect of a bird-to-bird transmission on the transmission dynamics of this virus is studied through mathematical modeling. The model still treats the bird-to-mosquito-to-bird as the main transmission route. The results of numerical calculations show that there are changes in the dynamics of the transmission of West Nile fever in humans when the non-mosquito transmission route becomes more important.