Amelia Travassos da Rosa

Probable Non–Vector-borne Transmission of Zika Virus, Colorado, USA

Clinical and serologic evidence indicate that 2 American scientists contracted Zika virus infections while working in Senegal in 2008. One of the scientists transmitted this arbovirus to his wife after his return home. Direct contact is implicated as the transmission route, most likely as a sexually transmitted infection.

Immunization with heterologous flaviviruses protective against fatal west Nile encephalitis

Prior immunization of hamsters with three heterologous flaviviruses (Japanese encephalitis virus [JEV] SA14-2-8 vaccine, wild-type St. Louis encephalitis virus [SLEV], and Yellow fever virus [YFV] 17D vaccine) reduces the severity of subsequent West Nile virus (WNV) infection. Groups of adult hamsters were immunized with each of the heterologous flaviviruses; approximately 30 days later, the animals were injected intraperitoneally with a virulent New York strain of WNV. Subsequent levels of viremia, antibody response, and deaths were compared with those in nonimmune (control) hamsters. Immunity to JEV and SLEV was protective against clinical encephalitis and death after challenge with WNV. The antibody response in the sequentially infected hamsters also illustrates the difficulty in making a serologic diagnosis of WNV infection in animals (or humans) with preexisting Flavivirus immunity.

An outbreak of dengue virus at Rio de Janeiro - 1986

Dengue virus type 1 has been isolated in Aedes albopictus cell strain, from sera of patients living in the Nova Iguaçu county, by Rio de Janeiro. The clinical picture was characterized by fever, headache, retrobulbar pain, backache, pains in the muscles and the joints and prostration. Studies in paired sera confirmed the presence of recent infection by dengue virus type 1. The outbreak reached adjacent areas, including Rio de Janeiro city (May, 1986).

West Nile virus in Mexico: evidence of widespread circulation since July 2002.

West Nile virus (WNV) antibodies were detected in horses from five Mexican states, and WNV was isolated from a Common Raven in the state of Tabasco. Phylogenetic studies indicate that this isolate, the first from Mexico, is related to strains from the central United States but has a relatively high degree of sequence divergence.

Efficacy of Killed Virus Vaccine, Live Attenuated Chimeric Virus Vaccine, and Passive Immunization for Prevention of West Nile virus Encephalitis in Hamster Model

Results of experiments evaluating the efficacy of three immunization strategies for the prevention of West Nile virus (WNV) encephalitis are reported. Immunization strategies evaluated included a killed virus veterinary vaccine, a live attenuated chimeric virus vaccine candidate, and passive immunization with WNV-immune serum; all were tested by using a hamster model of the disease. Each product protected the animals from clinical illness and death when challenged with a hamster-virulent wild-type WNV strain 1 month after initial immunization. The live attenuated chimeric virus vaccine candidate induced the highest humoral antibody responses, as measured by hemagglutination inhibition, complement fixation, and plaque reduction neutralization tests. Although the duration of protective immunity was not determined in this study, our preliminary results and the cumulative experience of other virus vaccines suggest that the live attenuated chimeric virus provides the longest lasting immunity.

Persistent West Nile Virus Infection in the Golden Hamster: Studies on Its Mechanism and Possible Implications for Other Flavivirus Infections

Golden hamsters (Mesocricetus auratus) experimentally infected with West Nile virus (WNV) developed chronic renal infection and persistent shedding of virus in urine for up to 8 months, despite initial rapid clearance of virus from blood and the timely appearance of high levels of specific neutralizing antibodies. Infectious WNV could be recovered by direct culture of their urine and by cocultivation of kidney tissue for up to 247 days after initial infection. Only moderate histopathologic changes were observed in the kidneys or brain of the chronically infected hamsters, although WNV antigen was readily detected by immunohistochemistry within epithelium, interstitial cells, and macrophages in the distal renal tubules. Comparison of WNV isolates from serial urine samples from individual hamsters over several months indicated that the virus underwent both genetic and phenotypic changes during persistent infection. These findings are similar to previous reports of persistent infection with tickborne encephalitis and Modoc viruses.

Experimental Yellow Fever Virus Infection in the Golden Hamster (Mesocricetus auratus). I. Virologic, Biochemical, and Immunologic Studies

This report describes the clinical laboratory findings in golden hamsters experimentally infected with yellow fever (YF) virus. An accompanying paper describes the pathologic findings. Following intraperitoneal inoculation of a virulent strain of YF virus, hamsters developed a high-titered viremia (up to 109/mL) lasting 5--6 days and abnormal liver function tests. YF hemagglutination-inhibiting antibodies appeared 4 or 5 days after infection, often while viremia was still present. The mortality rate in YF-infected hamsters was variable, depending on the virus strain and the age of the animals. Clinical and pathologic changes in the infected hamsters were very similar to those described in experimentally infected macaques and in fatal human cases of YF, which indicates that the golden hamster may be an excellent alternative animal model, in place of nonhuman primates, for research on the pathogenesis and treatment of YF and other viscerotropic flavivirus diseases.

Inadequate management of natural ecosystem in the Brazilian Amazon region results in the emergence and reemergence of arboviruses

A total of 187 different species of arboviruses and other viruses in vertebrates were identified at the Evandro Chagas Institute (IEC) from 1954 to 1998, among more than 10,000 arbovirus strains isolated from humans, hematophagous insects, and wild and sentinel vertebrates. Despite intensive studies in the Brazilian Amazon region, especially in Pará State, very little is known about most of these viruses, except for information on date, time, source, and method of isolation, as well as their capacity to infect laboratory animals. This paper reviews ecological and epidemiological data and analyzes the impact of vector and host population changes on various viruses as a result of profound changes in the natural environment. Deforestation, mining, dam and highway construction, human colonization, and urbanization were the main manmade environmental changes associated with the emergence and/or reemergence of relevant arboviruses, including some known pathogens for humans.

Limited evolution of West Nile virus has occurred during its southwesterly spread in the United States

Analysis of partial nucleotide sequences of nine West Nile virus strains isolated in southeast Texas during June-August 2002 revealed a maximum of 0.35% nucleotide variation from a New York 1999 strain. Two sequence subtypes were identified that differed from each other by approximately 0.5%, suggesting multiple introductions of virus to this area. Analysis of sequences from cloned PCR products for one strain revealed up to 0.6% divergence from the consensus sequence at the subpopulation level. The presence of unique patterns of small numbers of mutations in North American West Nile strains studied to date may suggest the absence of a strong selective pressure to drive the emergence of dominant variants.

Epidemia de dengue em Fortaleza, Ceará: inquérito soro-epidemiológico aleatório

OBJETIVO: Seguindo-se a epidemia de dengue (DEN), em 1994, em Fortaleza, Ceara, causada pelo sorotipo 2 (DEN-2), realizou-se inquerito soro-epidemiologico aleatorio para avaliar e dimensionar o impacto da mesma e a prevalencia do dengue por distrito sanitario. METODO: Foi aplicado questionario contendo informacoes gerais, condicoes socio-economicas, informacoes sobre o quadro clinico e tempo de doenca. A amostra foi calculada para estimar uma prevalencia de 20%, com erro relativo de 10%, e intervalo de confianca de 95% (erro a de 5%). O sorteio e as analises foram realizadas por meio de computador usando programas apropriados. RESULTADOS E CONCLUSOES: Foram colhidas 1.341 amostras de soro de 9 distritos sanitarios, testadas por inibicao da hemaglutinacao, sendo classificadas como negativas e positivas (respostas primaria - RP e secundaria - RS). Foram reativas 588 (44%) amostras, sendo 93 (7%) RP e 495 (37%) RS. A prevalencia global em Fortaleza variou de 21% a 71%. Houve 41% (243/588) de infeccoes assintomaticas (IA) e 59% (346/588) sintomaticas (IS). Nao houve diferenca da prevalencia quanto ao sexo, faixa etaria e escolaridade, ao contrario da condicao socioeconomica que apresentou diferencas estatisticamente significantes (p < 0,001). Ocorreram mais IA (p<0,001) e IS (p<0,0001) em casos de RS que RP, com significância estatistica em ambos os sexos. Os sintomas mais prevalentes no casos confirmados foram febre, cefaleia, mialgias, exantema, mal estar geral, tontura e artralgias, sendo que prurido, dor ocular, exantema e gengivorragia foram estatisticamente significantes (p<0,005). Tontura e artralgias foram mais associados com RS que com RP, havendo diferencas estatisticas (p <0,05).OBJECTIVE A seroepidemiological random survey was carried out in Fortaleza city, State of Ceará, Brazil, following an epidemic of dengue virus type 2 (DEN 2), with the purpose of evaluating the frequency of clinical manifestations (signs and symptoms) and the prevalence of dengue infection. METHOD A questionnaire calling for information on address, sex, age, clinical, epidemiological and economic status was applied to the population, followed by venupuncture collection of 5-10 ml of blood for testing by hemagglutination-inhibition (HI). The sample was calculated to obtain a prevalence of 20% with relative risk of 10% and confidence interval of 95%. All information obtained was analyzed by computer using Epi Info 5.0, Lotus 123, Excel 5.0, and Stata software. RESULTS AND CONCLUSIONS A total of 1,341 serum samples were obtained from nine Health Districts (SD) and tested by hemagglutination inhibition. Of these, 589 (44%) were positive and 752 (56%) negative. Of the positive results, 93 primary responses (PR) (7%) to DEN-2 and 496 secondary responses (SR) (37%) were observed. The global prevalence in the SD ranged from 21% to 71%. There were 41% (243/589) asymptomatic infections and 59% (346/589) symptomatic infections. Data analysis showed no difference in frequency by sex, age, on schooling, although a highly statistically significant difference was found as between the different social classes, the infection most commonly observed being among people of better social status. The stratification of positive cases showed greater prevalence of AI (p < 0.001) and SI (p < 0.0001) in both sexes, among people with SR rather than PR. The most prevalent symptoms were fever, headache, muscle pains, rash, dizziness, and joint pains. Moreover, itching, retro-bulbar pain, rash, and gingival bleeding, showed statistically significant differences. On the other hand, dizziness and joint pains were more associated in the patients with SR than PR, and statistically significant differences were also observed.