Isolamento no território federal do Amapá de um vírus nôvo relacionado sorològicamente aos agentes responsáveis pelas febres hemorrágicas da Argentina e da Bolívia / Isolation in the Federal Territory of Amapá of a new virus serologically related to the agents responsible for hemorrhagic fever in Argentina and Bolivia

Um nôvo membro do grupo Tacaribe, o vírus Amapari, tem sido inoculado repetidas vêzes das vísceras e sangue de Oryzomys e Neacomys, capturados em SN, Território Federal do Amapá. Um único isolamento foi obtido da urina das crias e de ectoparasitos dêsses animais. Os autores analisam algumas implicações ecológicas, bem como do ponto de vista de patogenicidade humana do referido agente. Referem, ainda, a importância da prova de FC’ como recurso de grande valor no isolamento dêste vírus, uma vez que os camundongos inoculados com os espécimens provenientes de animais infectados freqüentemente desenvolvem infecção inaparente.

A new member of the Tacaribe group, Amapari virus, has been repeatedly isolated from the viscera and blood of rodents belonging to the genera Oryzomys and Neacomys captured in the Serra do Navio region, Federal Territory of Amapá, Brazil. Single isolations were also obtained from the urine, young, and ectoparasites of these animals. The authors discuss certain aspects of the epizootiology of the above mentioned virus, with special reference to its pathogenicity in man. They also refer the importance of FC’ test as a tool of great value for isolation of this virus, since mice inoculated with specimens obtained from infected animals frequently develop inapparent infection.

Eradication of wild poliovirus from the Americas: wild poliovirus surveillance--laboratory issues.

The Pan American Regional Poliomyelitis Laboratory Network, developed to support the program to eradicate indigenous wild poliovirus transmission in the Americas, included 10 laboratories, distributed in eight countries in the Americas, organized according to the diagnostic procedures they regularly performed. All laboratories isolated and typed virus in stool specimens, several did intratypic differentiation by nucleic acid probe hybridization, and 2 sequenced wild poliovirus isolates for molecular epidemiologic studies. High performance of the network was maintained through comprehensive training of virologists, continuous monitoring of laboratory performance, and prompt investigation of problems. Recommended field and laboratory procedures were regularly reviewed and revised to optimize sensitivity, specificity, and diagnostic efficiency. Close integration of field and laboratory surveillance was achieved through frequent meetings between virologists and epidemiologists, effective communication of program priorities, and the distribution of weekly surveillance reports.

Global situation of dengue and dengue haemorrhagic fever, and its emergence in the Americas.

About two-thirds of the world's population live in areas infested with dengue vectors, mainly Aedes aegypti. All four dengue viruses are circulating, sometimes simultaneously, in most of these areas. It is estimated that up to 80 million persons become infected annually although marked underreporting results in the notification of much smaller figures. Currently dengue is endemic in all continents except Europe and epidemic dengue haemorrhagic fever (DHF) occurs in Asia, the Americas and some Pacific islands. The incidence of DHF is much greater in the Asian countries than in other regions. In Asian countries the disease continues to affect children predominantly although a marked increase in the number of DHF cases in people over 15 years old has been observed in the Philippines and Malaysia during recent years. In the 1990's DHF has continued to show a higher incidence in South-East Asia, particularly in Viet Nam and Thailand which together account for more than two-thirds of the DHF cases reported in Asia. However, an increase in the number of reported cases has been noted in the Philippines, Lao People's Democratic Republic, Cambodia, Myanmar, Malaysia, India, Singapore and Sri Lanka during the period 1991-1995 as compared to the preceding 5-year period. In the Americas, the emergence of epidemic DHF occurred in 1981 almost 30 years after its appearance in Asia, and its incidence is showing a marked upward trend. In 1981 Cuba reported the first major outbreak of DHF in the Americas, during which a total of 344,203 cases of dengue were notified, including 10,312 severe cases and 158 deaths. The DHF Cuban epidemic was associated with a strain of dengue-2 virus and it occurred four years after dengue-1 had been introduced in the island causing epidemics of dengue fever. Prior to this event suspected cases of DHF or fatal dengue cases had been reported by five countries but only a few of them fulfilled the WHO criteria for diagnosis of DHF. The outbreak in Cuba is the most important event in the history of dengue in the Americas. Subsequently to it, in every year except 1983, confirmed or suspected cases of DHF have been reported in the Region. The second major outbreak in the Americas occurred in Venezuela in 1989 and since then this country has suffered epidemics of DHF every year. Between 1981 and 1996 a total of 42,246 cases of DHF and 582 deaths were reported by 25 countries in the Americas, 53% of which originated from Venezuela and 24% from Cuba. Colombia, Nicaragua and Mexico have each reported over 1,000 cases during the period 1992-1996. About 74% of the Colombian cases and 97% of the Mexican cases were reported during 1995-1996. A main cause of the emergence of DHF in the Americas was the failure of the hemispheric campaign to eradicate Aedes aegypti. Following a successful period that resulted in the elimination of the mosquito from 18 countries by 1962, the programme began to decline and as a result there was a progressive dissemination of the vector so that by 1997 with the exception of Canada, Chile and Bermuda, all countries in the Americas are infested. Other factors contributing to the emergence/re-emergence of dengue/DHF include the rapid growth and urbanization of populations in Latin America and the Caribbean, and increased travel of persons which facilitates dissemination of dengue viruses. Presently, all four dengue serotypes are circulating in the Americas, thus increasing the risk for DHF in this region.

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.

Eradication of poliomyelitis: progress in the Americas.

In the span of 5 years since the eradication initiative was launched and only 3 years since external funds were made available, PAHO has been able to develop and implement a comprehensive program strategy for polio eradication that includes the following components: achievement and maintenance of high immunization levels (which include the supplemental strategies of national immunization days and mop-up operations); effective surveillance to detect all new cases; and a rapid response to the occurrence of new cases. Despite yearly increases in the number of cases of acute flaccid paralysis reported to the surveillance system, a decline in reported confirmed cases of polio has occurred since 1986 to record low levels in 1989. Cases in 1989 were reported from only 0.7% of the counties in the Americas. The occurrence of 24 wild-type virus isolates in 1989 were limited to only three geographic areas: northwestern Mexico; the northern Andean Region; and northeastern Brazil. At this writing the clock is ticking with only 3 months left to achieve the goal of interrupting transmission by the end of 1990. If the current level of effort is sustained and special efforts are directed at the remaining foci of infection, the eradication of the transmission of wild-type poliovirus from the Americas can be achieved. Continued external financial support will be critical if the effort is to succeed. The prospect of poliomyelitis eradication in the Americas led the 41st World Health Assembly of WHO to adopt a resolution in May, 1988, to eradicate the indigenous transmission of wild-type poliovirus from the world by the year 2000.(ABSTRACT TRUNCATED AT 250 WORDS)

Host-seeking behavior and seasonal abundance of Culicoides paraensis (Diptera: Ceratopogonidae) in Brazil.

The ecology of Culicoides paraensis was studied with human bait collections at an agricultural research station near Belém and within 2 neighborhoods of Belém, Brazil, from 1977 to 1978. From collections conducted along transects that were centered on a house, we found most dense populations of host-seeking midges within and near the house. Host-seeking activity was least in areas fully exposed to sunlight compared to the levels of activity indoors and in shaded areas outside. Numbers of flies biting under shade trees and within the house increased during intervals of rain; concomitantly the levels of activity decreased in open areas. Seasonal population densities correlated with the pattern of rainfall, with a 2-month lag due to the long maturation time of immature C. paraensis. The effects of temperature and humidity on host-seeking activity are discussed.

Global survey of antibody to Hantaan-related viruses among peridomestic rodents.

A global serological survey of rodents was conducted to determine the distribution and prevalence of antibody to Hantaan-related viruses, which are the causative agents of haemorrhagic fever with renal syndrome (HFRS) in man. Over 1700 rodent sera from more than 20 sites worldwide were examined by immunofluorescent antibody assay. High-titred positive sera were further tested by plaque reduction neutralization tests with prototype Hantaan virus and urban rat-associated Hantaan-like virus. Antibody-positive rodents were found in most, but not all, sites sampled. The highest antibody prevalence rates were found in Baltimore, MD, USA and Bélem, Brazil, and Rattus norvegicus was the species most often found positive. Bandicota indica and B. bengalensis, species previously not recognized as hosts of hantaviruses, were also positive. Neutralization tests detected antibody in Rattus sera specific for urban rat-associated Hantaan-like virus, but failed to establish the specificity of antibody in Bandicota sera. These results indicate that Hantaan-related viruses exist beyond the currently recognized boundaries of HFRS in man and suggest that human HFRS-like disease might be occurring in other areas of the world where rodent-human contact is common.

Isolation of a Hantaan-related virus from Brazilian rats and serologic evidence of its widespread distribution in South America.

A serosurvey of domestic rats was conducted in several South American cities between September 1982 and March 1983 for evidence of hantavirus infection. Antibody-positive rats were found in Belem, São Paulo and Recife-Olinda, Brazil and in Buenos Aires, Argentina, with the highest antibody prevalence rate detected in Belem (30 positive of 54 tested, 56%). A virus isolated from tissues of a Rattus norvegicus captured in Belem, was shown to be antigenically similar to Girard Point viruses isolated from domestic rats captured in the United States and clearly distinct from prototype Hantaan virus, causative agent of Korean hemorrhagic fever in Asia. This represents the first isolation of a virus of the genus Hantavirus from South America and supports previous observations that indicate a widespread distribution of urban rat-associated hantaviruses. The abundance of domestic rats and their regionally high antibody rates suggest that risk of human hantavirus infection in some locations of South America may be significant.

Characterization of the Changuinola serogroup viruses (Reoviridae: Orbivirus).

The antigenic, biological, and chemical properties of 24 selected Changuinola serogroup viruses were examined. The viruses tested were chloroform-resistant, and they were lethal to newborn hamsters after intracerebral inoculation. The prototype Changuinola virus strain (BT-436) replicated in mosquito and sandfly cell cultures. In complement-fixation tests, the viruses were broadly cross-reacting and indistinguishable; but by neutralization test at least 12 distinct serotypes were identified, and by PAGE of double-stranded RNA 22 distinct profiles were found. These data suggest that the Changuinola serogroup may be comprised of a large number of genetically different viruses. A brief review of the natural history of Changuinola serogroup viruses is also given.

Immunoperoxidase detection of Yellow Fever virus after natural and experimental infections.

Accurate diagnosis of fatal Yellow Fever (YF) is important for surveillance and prevention of epidemics in regions where the virus is endemic. Immunoperoxidase (IP) staining for viral antigens offers a means to both document infection and investigate pathogenic mechanisms. We developed an indirect IP staining assay for YF, which was used to detect YF antigen in histologic sections of human liver from patients with fatal natural infections, and suckling mouse brains experimentally inoculated with an unattenuated neurotropic strain of YF virus. In human liver, specific IP staining was present in the cytoplasm of hepatocytes, but in mouse brain, specific IP staining was localized within nuclei of neurons. The distribution of IP staining corresponded to the location of degenerative morphologic changes within cells; however, IP staining was more widespread than expected on the basis of histopathologic lesions. Furthermore, the degree of inflammation was disproportionately mild compared to the extent of infection, i.e. distribution of YF antigen, both in human liver and suckling mouse brain. The results suggest that the pathogenesis of YF in humans and suckling mice is overwhelming viral infection with minimal associated host immunological and/or inflammatory response in tissues.

Characterization of eight new phlebotomus fever serogroup arboviruses (Bunyaviridae: Phlebovirus) from the Amazon region of Brazil.

Eight new members of the phlebotomus fever arbovirus serogroup (family Bunyaviridae; genus Phlebovirus) from the Amazon region of Brazil are described. One serotype was recovered from a febrile patient, three from small wild animals and four from sand flies. A small serum survey carried out with the human isolate, Alenquer virus, suggests that it rarely infects man. Complement-fixation and plaque reduction neutralization tests were done, comparing the eight new viruses with other members of the phlebotomus fever serogroup. A close antigenic relationship was demonstrated between one of the new agents (Belterra) and Rift Valley fever virus. This finding is of considerable interest and deserves further investigation. Addition of these eight new viruses to the genus Phlebovirus brings to 14 the number of serotypes known to occur in the Amazon region and to 36 the total number reported worldwide. More detailed clinical and epidemiological studies should be conducted in Amazonia in order to define the public health impact caused by phleboviruses.