Genomic and epidemiological monitoring of yellow fever virus transmission potential

The yellow fever virus (YFV) epidemic in Brazil is the largest in decades. The recent discovery of YFV in Brazilian Aedes species mosquitos highlights a need to monitor the risk of reestablishment of urban YFV transmission in the Americas. We use a suite of epidemiological, spatial, and genomic approaches to characterize YFV transmission. We show that the age and sex distribution of human cases is characteristic of sylvatic transmission. Analysis of YFV cases combined with genomes generated locally reveals an early phase of sylvatic YFV transmission and spatial expansion toward previously YFV-free areas, followed by a rise in viral spillover to humans in late 2016. Our results establish a framework for monitoring YFV transmission in real time that will contribute to a global strategy to eliminate future YFV epidemics.

Molecular epidemiology of type 1 and 2 dengue viruses in Brazil from 1988 to 2001

Dengue is a mosquito-borne viral infection that in recent decades has become a major international public health concern. Epidemic dengue fever reemerged in Brazil in 1981. Since 1990 more than one dengue virus serotype has been circulating in this tropical country and increasing rates of dengue hemorrhagic fever and dengue shock syndrome have been detected every year. Some evidence supports the association between the introduction of a new serotype and/or genotype in a region and the appearance of dengue hemorrhagic fever. In order to study the evolutionary relationships and possible detection of the introduction of new dengue virus genotypes in Brazil in the last years, we analyzed partial nucleotide sequences of 52 Brazilian samples of both dengue type 1 and dengue type 2 isolated from 1988 to 2001 from highly endemic regions. A 240-nucleotide-long sequence from the envelope/nonstructural protein 1 gene junction was used for phylogenetic analysis. After comparing the nucleotide sequences originally obtained in this study to those previously studied by others, and analyzing the phylogenetic trees, we conclude that, after the initial introduction of the currently circulating dengue-1 and dengue-2 genotypes in Brazil, there has been no evidence of introduction of new genotypes since 1988. The increasing number of dengue hemorrhagic fever cases seen in Brazil in the last years is probably associated with secondary infections or with the introduction of new serotypes but not with the introduction of new genotypes.

Phenotypic and molecular analyses of yellow fever 17DD vaccine viruses associated with serious adverse events in Brazil

The yellow fever (YF) 17D virus is one of the most successful vaccines developed to data. Its use has been estimated to be over 400 million doses with an excellent record of safety. In the past 3 years, yellow fever vaccination was intensified in Brazil in response to higher risk of urban outbreaks of the disease. Two fatal adverse events temporally associated with YF vaccination were reported. Both cases had features similar to yellow fever disease, including hepatitis and multiorgan failure. Two different lots of YF 17DD virus vaccine were administered to the affected patients and also to hundreds of thousands of other individuals without any other reported serious adverse events. The lots were prepared from the secondary seed, which has been in continuous use since 1984. Nucleotide sequencing revealed minor variations at some nucleotide positions between the secondary seed lot virus and the virus isolates from patients; these differences were not consistent across the isolates, represented differences in the relative amount of each nucleotide in a heterogeneous position, and did not result in amino acid substitutions. Inoculation of rhesus monkeys with the viruses isolated from the two patients by the intracerebral (ic) or intrahepatic (ih) route caused minimal viremia and no clinical signs of infection or alterations in laboratory markers. Central nervous system histological scores of rhesus monkeys inoculated ic were within the expected range, and there were no histopathological lesions in animals inoculated ih. Altogether, these results demonstrated the genetic stability and attenuated phenotype of the viruses that caused fatal illness in the two patients. Therefore, the fatal adverse events experienced by the vaccinees are related to individual, genetically determined host factors that regulate cellular susceptibility to yellow fever virus. Such increased susceptibility, resulting in clinically overt disease expression, appears to be extremely rare.

Serious adverse events associated with yellow fever 17DD vaccine in Brazil: a report of two cases

BACKGROUND

The yellow fever vaccine is regarded as one of the safest attenuated virus vaccines, with few side-effects or adverse events. We report the occurrence of two fatal cases of haemorrhagic fever associated with yellow fever 17DD substrain vaccine in Brazil.

METHODS

We obtained epidemiological, serological, virological, pathological, immunocytochemical, and molecular biological data on the two cases to determine the cause of the illnesses.

FINDINGS

The first case, in a 5-year-old white girl, was characterised by sudden onset of fever accompanied by headache, malaise, and vomiting 3 days after receiving yellow fever and measles-mumps-rubella vaccines. Afterwards she decompensated with icterus and haemorrhagic signs and died after a 5-day illness. The second patient-a 22-year-old black woman-developed a sore throat and fever accompanied by headache, myalgia, nausea, and vomiting 4 days after yellow fever vaccination. She then developed icterus, renal failure, and haemorrhagic diathesis, and died after 6 days of illness. Yellow fever virus was recovered in suckling mice and C6/36 cells from blood in both cases, as well as from fragments of liver, spleen, skin, and heart from the first case and from these and other viscera fragments in case 2. RNA of yellow fever virus was identical to that previously described for 17D genomic sequences. IgM ELISA tests for yellow fever virus were negative in case 1 and positive in case 2; similar tests for dengue, hantaviruses, arenaviruses, Leptospira, and hepatitis viruses A-D were negative. Tissue injuries from both patients were typical of wild-type yellow fever.

INTERPRETATION

These serious and hitherto unknown complications of yellow fever vaccination are extremely rare, but the safety of yellow fever 17DD vaccine needs to be reviewed. Host factors, probably idiosyncratic reactions, might have had a substantial contributed to the unexpected outcome.

First isolation of dengue 3 in Brazil from an imported case

The authors report the isolation of dengue 3 virus for the first time in Brazil. The patient, resident in Limeira-SP, traveled to Nicaragua on May 16th, 1998, where he stayed for two months. Starting on August 14 th he had fever, headache, myalgia, arthralgia, retro-orbital pain and diarrhea. He returned to Brazil on August 16th and was hospitalized in the next day. The patient had full recovery and was discharged on August 20th. The virus was isolated in C6/36 cell culture inoculated with serum collected on the 6th day after the onset of the symptoms. The serotype 3 was identified by indirect immunofluorescence assays performed with type-specific monoclonal antibodies. This serotype was further confirmed by polymerase chain reaction analysis. The introduction of a new dengue serotype in a susceptible population is a real threat for the occurrence of severe forms of the disease. The isolation and identification of dengue virus are important in order to monitoring the serotypes circulating in Brazil and to take the measures necessary to prevent and control an epidemic.

Human disease caused by an arbovirus closely related to Ilheus virus: report of five cases

We report five cases of human disease caused by arbovirus in 5 patients from the State of São Paulo, Brazil, residing in the municipalities of Osasco, Atibaia, Guarujá, and the capital São Paulo, respectively. One of the patients resides in São Luis, capital of the State of Maranhão. The sites of infection probably were the states of Paraná and Goiás, both in cave regions, the State of Amazonas, and Rondônia in two cases. Laboratory tests for malaria were negative and 1 patient showed a positive serum reaction for leptospirosis. Serum samples from the acute and convalescent phases were tested by hemagglutination inhibition, complement fixation, and neutralization in mice. Acute phase samples were inoculated into suckling mice by the intracerebral route. A close antigenic relationship was observed between the five agents isolated and the flavivirus Ilheus. Serologic tests demonstrated the absence of antibodies in all samples from the 5 patients during convalescence and even for more than 1 year after infection in 1 of them.

Simultaneous infection with dengue 1 and 2 in a Brazilian patient

Dengue outbreaks have occurred in several Brazilian States since 1986 involving serotypes 1 (DEN-1) and 2 (DEN-2). In view of the few cases of double infection documented in the literature, we report here a case of simultaneous infection with DEN-1 and DEN-2 in a patient residing in the municipality of Miranda, State of Mato Grosso do Sul, Western region of Brazil. DEN-1 was introduced in this State in 1989 and DEN-2 in 1996, both of them circulating in some municipalities. This double infection was identified by virus isolation and by indirect immunofluorescence using monoclonal antibodies and confirmed by the polymerase chain reaction (PCR). This is the first documented case of simultaneous infection with serotypes DEN-1 and DEN-2 in Brazil.

Jungle yellow fever: clinical and laboratorial studies emphasizing viremia on a human case

The authors report the clinical, laboratorial and epidemiological aspects of a human case of jungle yellow fever. The patient suffered from fever, chills, sweating, headaches, backaches, myalgia, epigastric pains, nausea, vomiting, diarrhea and prostration. He was unvaccinated and had been working in areas where cases of jungle yellow fever had been confirmed. Investigations concerning the yellow fever virus were performed. Blood samples were collected on several days in the course of the illness. Three of these samples (those obtained on days 5, 7 and 10) were inoculated into suckling mice in attempt to isolate virus and to titrate the viremia level. Serological surveys were carried out by using the IgM Antibodies Capture Enzyme Linked Immunosorbent Assay (MAC-ELISA), Complement Fixation (CF), Hemagglutination Inhibition (HI) and Neutralization (N) tests. The yellow fever virus, recovered from the two first samples and the virus titration, showed high level of viremia. After that, specific antibodies appeared in all samples. The interval between the end of the viremia and the appearance of the antibodies was associated with the worsening of clinical symptoms, including bleeding of the mucous membrane. One must be aware of the risk of having a urban epidemics in areas where Aedes aegypti is found in high infestation indexes.

Surveillance of arbovirus infections in the Atlantic Forest Region, State of São Paulo, Brazil. I. Detection of hemagglutination-inhibiting antibodies in wild birds between 1978 and 1990

We report data related to arbovirus antibodies detected in wild birds periodically captured from January 1978 to December 1990 in the counties of Salesópolis (Casa Grande Station), Itapetininga and Ribeira Valley, considering the different capture environments. Plasmas were examined using hemagglutination-inhibition (HI) tests. Only monotypic reactions were considered, except for two heterotypic reactions in which a significant difference in titer was observed for a determined virus of the same antigenic group. Among a total of 39,911 birds, 269 birds (0.7%) belonging to 66 species and 22 families were found to have a monotypic reaction for Eastern equine encephalitis (EEE), Venezuelan equine encephalitis (VEE), Western equine encephalitis (WEE), Ilheus (ILH), Rocio (ROC), St. Louis encephalitis (SLE), SP An 71686, or Caraparu (CAR) viruses. Analysis of the data provided information of epidemiologic interest with respect to these agents. Birds with positive serology were distributed among different habitats, with a predominance of unforested habitats. The greatest diversity of positive reactions was observed among species which concentrate in culture fields.

New arenavirus isolated in Brazil

A new arenavirus, called Sabiá, was isolated in Brazil from a fatal case of haemorrhagic fever initially thought to be yellow fever. Antigenic and molecular characterisation indicated that Sabiá virus is a new member of the Tacaribe complex. A laboratory technician working with the agent was also infected and developed a prolonged, non-fatal influenza-like illness. Sabiá virus is yet another arenavirus causing human disease in South America.

Iguape: a newly recognized flavivirus from São Paulo State, Brazil

A new virus, SP An 71686, was isolated from sentinel mice exposed in a forest area in Iguape county, São Paulo state, Brazil, in 1979. The results suggest [hemagglutination inhibition (HI), complement fixation, neutralization, and ELISA] that SP An 71686 virus is a new arbovirus and that it demonstrates some cross-reactivity with other members of the family Flaviviridae, but can be differentiated from them. Although there is an intensive circulation of several arboviruses in the area, the only diagnosed cases of human disease were caused by Rocio virus during and after the epidemic of encephalitis that occurred in 1975-1977, one case of febrile illness by Caraparu virus in 1983, and by subtype IF of Venezuelan equine encephalitis virus in soldiers during jungle survival training in 1990. Wild animals had a prevalence of SP An 71686 HI monotype antibodies: 46% of birds captured in 1990, 40% in 1991 and 19.5% in 1992. These results suggested that wild birds may play a role in the virus transmission cycle. Mammals (rodents and marsupials) must also be considered potential hosts. However, the virus reservoir-vector relationships need further studies which would help to clarify the ecology of this virus.