Identification of new Guama and Group C serogroup bunyaviruses and an ungrouped virus from Southern Brazil.

From 1975 to 1978, 36 viruses were recovered from humans, bats, birds, sentinel mice and hamsters, and from mosquitoes collected in Coastal Brazil in the state of São Paulo. Identifications of 22 of these 36 viruses have been reported. Six of the remaining 14 isolates were shown to be Guama serogroup bunyaviruses. Two of these six were strains of a newly recognized virus for which the name Cananeia virus is proposed; another is a second newly recognized Guama serogroup virus for which the name Itimirim virus is proposed; a fourth is a strain of Bertioga virus and the other two are strains of Guaratuba virus. Before these studies Guaratuba virus was considered an ungrouped bunyavirus, but cross testing by complement-fixation demonstrated that this virus, and Mirim virus as well, should be considered members of the Guama serogroup. Another six viruses were shown to be strains of a single, newly recognized Group C bunyavirus for which the name Bruconha virus is proposed. Two strains of a single virus were shown by electron microscopy to belong to the family Bunyaviridae, but serologic relationships with other members of this family of viruses were not found; the name Enseada virus is proposed for this newly recognized agent.

Emergence of a new arbovirus disease in Brazil. III. Isolation of Rocio virus from Psorophora Ferox (Humboldt, 1819).

A newly described flavivirus was responsible for a large encephalitis epidemic in São Paulo State, Brazil. The etiologic agent, Rocio virus, was isolated from human patients and sentinel mice. The natural history of the virus is unknown although presumed to be arthropod-borne. Rocio virus was isolated from a single pool containing 19 Psorophora ferox of 47 pools (283 specimens) of this species tested. The positive pool contained 16 deplete, 2 gravid, and 2 engorged mosquitoes. No isolations were made from 2183 pools of other species. The positive pool was collected during the year of the epidemic at the same approximate time and place where vertebrate isolations were made.

Isolation of St. Louis encephalitis virus in South Brazil.

Eight strains of a flavivirus identified as St. Louis encephalitis (SLE) virus were isolated from wild rodents, birds, and sentinel mice in three locations in the State of São Paulo, Brazil from 1967--1969. No illness attributable to SLE virus infection was detected among the local inhabitants, although about 5% of the local population had neutralizing antibodies to this virus.

Emergence of a new arbovirus disease in Brazil. II. Epidemiologic studies on 1975 epidemic.

In April, 1975, an outbreak of human encephalitis caused by Rocio virus, a new flavivirus, occurred in the coastal region of southern São Paulo, Brazil. The epidemic started during the second half of March, 1975, and ended in June, 1975. A total of 465 cases with 61 deaths were recorded, and the overall attack rate was 15 per thousand population. The mortality rate was two per thousand inhabitants and the overall case-fatality rate was 13%. However, the case-fatality rate was markedly decreased when adequate hospital care was provided. The number of cases in the 15--30 years age group was higher than in the other age groups and the rate was higher in males than in females. Lack of evidence of person-to-person transmission, based on a study of families involved in the epidemic and on the antigenic relationship to other mosquito-borne flaviviruses, suggested that the virus was transmitted by a vector and that wild animals were involved in the virus cycle.

Emergence of a new arbovirus disease in Brazil. I. Isolation and characterization of the etiologic agent, Rocio virus.

In April, 1975, an epidemic of human encephalitis was detected in several counties in the State of São Paulo, Brazil; the epidemic continued into 1976. A virus was isolated from central nervous system (CNS) tissues of a 39-year-old male who died on December 8, 1975; the virus was found to be a new flavivirus for which the name Rocio virus is proposed. Nine further isolations of Rocio virus were obtained from CNS tissues of 17 patients who died with clinical symptoms of encephalitis. Isolations of virus and serologic evidence of Rocio virus infection in a significant proportion of the encephalitis patients suggested that Rocio virus was the etiologic agent of the epidemic. Rocio virus was isolated only from patients who died within 5 days of onset of illness. The virus was isolated from two sentinel mice exposed in the epidemic zone and from a rufous collared sparrow (Zonotrichia capensis) collected in the area.

Bertioga (Guama group) and Anhembi (Bunyamwera group), two new arboviruses isolated in São Paulo, Brazil.

Bertioga and Anhembi are two newly recognized arboviruses that were isolated in Saõ Paulo, Brazil. Bertioga was isolated from sentinel mice exposed in a forest of that name, and was shown to belong serologically to the Guama group of arboviruses. Anhembi, the second virus described, was isolated from pools of mosquitoes (Phoniomyia pilicauda and trichoprosopon pallidiventer), and from a spiny rat (Proechimys iheringi), and was shown to be a new member of the Bunyamwera group. The viruses are sensitive to sodium desoxycholate and are filterable through a millipore membrane of 450 mum pore size. Both are pathogenic for suckling mice and grow well in Vero cells, producing clear cytopathic effects. Detailed antigenic comparisons of Anhembi virus with other members of the Bunyamwera group isolated in the Americas, and of Bertioga virus with the members of the Guama group are presented. Both are believed to be new arboviruses in their groups.