Emergence of Human Arboviral Diseases in the Americas, 2000-2016.

In addition to individual or clusters of cases of human infections with arboviruses, the past 15 years has seen the emergence of newly recognized arboviruses and the re-emergence of others. Mentioned in this brief summary are Bourbon, Cache Valley, chikungunya, Heartland, Itaqui, Mayaro, Oropouche, Powassan, and Zika viruses, the latter being a remarkable occurrence.

Association of vectors and environmental conditions during the emergence of Peruvian horse sickness orbivirus and Yunnan orbivirus in northern Peru.

Since 1983, cases of diseased donkeys and horses with symptoms similar to those produced by alphaviruses were identified in two departments in northern Peru; however serological testing ruled out the presence of those viruses and attempts to isolate an agent were also unproductive. In 1997, also in northern Peru, two new orbiviruses were discovered, each recognized as a causative agent of neurological diseases in livestock and domestic animals and, at the same time, mosquitoes were found to be infected with these viruses. Peruvian horse sickness virus (PHSV) was isolated from pools of culicid mosquitoes, Aedes serratus and Psorophora ferox, and Yunnan virus (YUOV) was isolated from Aedes scapularis in the subtropical jungle (upper jungle) located on the slope between the east side of the Andes and the Amazonian basin in the Department of San Martín. Both viruses later were recovered from mosquitoes collected above the slope between the west side of the Andes and the coast (Department of Piura) in humid subtropical areas associated with the Piura River basin. In this region, PHSV was isolated from Anopheles albimanus and YUOV was isolated from Ae. scapularis. We discuss the ecology of vector mosquitoes during the outbreaks in the areas where these mosquitoes were found.

Bats and zoonotic viruses: can we confidently link bats with emerging deadly viruses?

An increasingly asked question is 'can we confidently link bats with emerging viruses?'. No, or not yet, is the qualified answer based on the evidence available. Although more than 200 viruses - some of them deadly zoonotic viruses - have been isolated from or otherwise detected in bats, the supposed connections between bats, bat viruses and human diseases have been raised more on speculation than on evidence supporting their direct or indirect roles in the epidemiology of diseases (except for rabies). However, we are convinced that the evidence points in that direction and that at some point it will be proved that bats are competent hosts for at least a few zoonotic viruses. In this review, we cover aspects of bat biology, ecology and evolution that might be relevant in medical investigations and we provide a historical synthesis of some disease outbreaks causally linked to bats. We provide evolutionary-based hypotheses to tentatively explain the viral transmission route through mammalian intermediate hosts and to explain the geographic concentration of most outbreaks, but both are no more than speculations that still require formal assessment.

Bats and zoonotic viruses: can we confidently link bats with emerging deadly viruses?

An increasingly asked question is 'can we confidently link bats with emerging viruses?'. No, or not yet, is the qualified answer based on the evidence available. Although more than 200 viruses - some of them deadly zoonotic viruses - have been isolated from or otherwise detected in bats, the supposed connections between bats, bat viruses and human diseases have been raised more on speculation than on evidence supporting their direct or indirect roles in the epidemiology of diseases (except for rabies). However, we are convinced that the evidence points in that direction and that at some point it will be proved that bats are competent hosts for at least a few zoonotic viruses. In this review, we cover aspects of bat biology, ecology and evolution that might be relevant in medical investigations and we provide a historical synthesis of some disease outbreaks causally linked to bats. We provide evolutionary-based hypotheses to tentatively explain the viral transmission route through mammalian intermediate hosts and to explain the geographic concentration of most outbreaks, but both are no more than speculations that still require formal assessment.

Orthobunyaviruses, a common cause of infection of livestock in the Yucatan peninsula of Mexico.

To determine the seroprevalence of selected orthobunyaviruses in livestock in the Yucatan Peninsula of Mexico, a serologic investigation was performed using serum samples from 256 domestic animals (182 horses, 31 sheep, 1 dog, 37 chickens, and 5 turkeys). All serum samples were examined by plaque reduction neutralization test using Cache Valley virus (CVV), Cholul virus (CHLV), South River virus (SOURV), Kairi virus, Maguari virus, and Wyeomyia virus. Of the 182 horses, 60 (33.0%) were seropositive for CHLV, 48 (26.4%) were seropositive for CVV, 1 (0.5%) was seropositive for SOURV, 60 (33.0%) had antibodies to an undetermined orthobunyavirus, and 13 (7.1%) were negative for orthobunyavirus-specific antibody. Of the 31 sheep, 6 (19.3%) were seropositive for CHLV, 3 (9.7%) were seropositive for CVV, 4 (12.9%) were seropositive for SOURV, 16 (51.6%) had antibodies to an undetermined orthobunyavirus, and 2 (6.5%) were negative for orthobunyavirus-specific antibody. The single dog was seropositive for SOURV. Four (11%) chickens had antibodies to an undetermined orthobunyavirus, and 1 (20%) turkey was seropositive for CHLV. These data indicate that orthobunyaviruses commonly infect livestock in the Yucatan Peninsula.

Tacaribe virus causes fatal infection of an ostensible reservoir host, the Jamaican fruit bat.

Tacaribe virus (TCRV) was first isolated from 11 Artibeus species bats captured in Trinidad in the 1950s during a rabies virus surveillance program. Despite significant effort, no evidence of infection of other mammals, mostly rodents, was found, suggesting that no other vertebrates harbored TCRV. For this reason, it was hypothesized that TCRV was naturally hosted by artibeus bats. This is in stark contrast to other arenaviruses with known hosts, all of which are rodents. To examine this hypothesis, we conducted experimental infections of Jamaican fruit bats (Artibeus jamaicensis) to determine whether they could be persistently infected without substantial pathology. We subcutaneously or intranasally infected bats with TCRV strain TRVL-11573, the only remaining strain of TCRV, and found that low-dose (10(4) 50% tissue culture infective dose [TCID(50)]) inoculations resulted in asymptomatic and apathogenic infection and virus clearance, while high-dose (10(6) TCID(50)) inoculations caused substantial morbidity and mortality as early as 10 days postinfection. Uninoculated cage mates failed to seroconvert, and viral RNA was not detected in their tissues, suggesting that transmission did not occur. Together, these data suggest that A. jamaicensis bats may not be a reservoir host for TCRV.

Peruvian horse sickness virus and Yunnan orbivirus, isolated from vertebrates and mosquitoes in Peru and Australia.

During 1997, two new viruses were isolated from outbreaks of disease that occurred in horses, donkeys, cattle and sheep in Peru. Genome characterization showed that the virus isolated from horses (with neurological disorders, 78% fatality) belongs to a new species the Peruvian horse sickness virus (PHSV), within the genus Orbivirus, family Reoviridae. This represents the first isolation of PHSV, which was subsequently also isolated during 1999, from diseased horses in the Northern Territory of Australia (Elsey virus, ELSV). Serological and molecular studies showed that PHSV and ELSV are very similar in the serotype-determining protein (99%, same serotype). The second virus (Rioja virus, RIOV) was associated with neurological signs in donkeys, cattle, sheep and dogs and was shown to be a member of the species Yunnan orbivirus (YUOV). RIOV and YUOV are also almost identical (97% amino acid identity) in the serotype-determining protein. YUOV was originally isolated from mosquitoes in China.

Temporal and geographic evidence for evolution of Sin Nombre virus using molecular analyses of viral RNA from Colorado, New Mexico and Montana.

BACKGROUND: All viruses in the family Bunyaviridae possess a tripartite genome, consisting of a small, a medium, and a large RNA segment. Bunyaviruses therefore possess considerable evolutionary potential, attributable to both intramolecular changes and to genome segment reassortment. Hantaviruses (family Bunyaviridae, genus Hantavirus) are known to cause human hemorrhagic fever with renal syndrome or hantavirus pulmonary syndrome. The primary reservoir host of Sin Nombre virus is the deer mouse (Peromyscus maniculatus), which is widely distributed in North America. We investigated the prevalence of intramolecular changes and of genomic reassortment among Sin Nombre viruses detected in deer mice in three western states. METHODS: Portions of the Sin Nombre virus small (S) and medium (M) RNA segments were amplified by RT-PCR from kidney, lung, liver and spleen of seropositive peromyscine rodents, principally deer mice, collected in Colorado, New Mexico and Montana from 1995 to 2007. Both a 142 nucleotide (nt) amplicon of the M segment, encoding a portion of the G2 transmembrane glycoprotein, and a 751 nt amplicon of the S segment, encoding part of the nucleocapsid protein, were cloned and sequenced from 19 deer mice and from one brush mouse (P. boylii), S RNA but not M RNA from one deer mouse, and M RNA but not S RNA from another deer mouse. RESULTS: Two of 20 viruses were found to be reassortants. Within virus sequences from different rodents, the average rate of synonymous substitutions among all pair-wise comparisons (pis) was 0.378 in the M segment and 0.312 in the S segment sequences. The replacement substitution rate (pia) was 7.0 x 10-4 in the M segment and 17.3 x 10-4 in the S segment sequences. The low pia relative to pis suggests strong purifying selection and this was confirmed by a Fu and Li analysis. The absolute rate of molecular evolution of the M segment was 6.76 x 10-3 substitutions/site/year. The absolute age of the M segment tree was estimated to be 37 years. In the S segment the rate of molecular evolution was 1.93 x 10-3 substitutions/site/year and the absolute age of the tree was 106 years. Assuming that mice were infected with a single Sin Nombre virus genotype, phylogenetic analyses revealed that 10% (2/20) of viruses were reassortants, similar to the 14% (6/43) found in a previous report. CONCLUSION: Age estimates from both segments suggest that Sin Nombre virus has evolved within the past 37-106 years. The rates of evolutionary changes reported here suggest that Sin Nombre virus M and S segment reassortment occurs frequently in nature.

Longitudinal studies of West Nile virus infection in avians, Yucatán State, México.

Following the introduction of West Nile virus (WNV) into North America in 1999, surveillance for evidence of infection with this virus in migratory and resident birds was established in Yucatán State, México in March 2000. Overall, 8611 birds representing 182 species and 14 orders were captured and assayed for antibodies to WNV. Of these, 5066 (59%) birds were residents and 3545 (41%) birds were migrants. Twenty-one (0.24%) birds exhibited evidence of flavivirus infection. Of these, 8 birds had antibodies to WNV by epitope-blocking enzyme-linked immunosorbent assay. Five (0.06%) birds (gray catbird, brown-crested flycatcher, rose-breasted grosbeak, blue bunting and indigo bunting) were confirmed to have WNV infections by plaque reduction neutralization test. The WNV-infected birds were sampled in December 2002 and January 2003. The brown-crested flycatcher and blue bunting presumably were resident birds; the other WNV seropositive birds were migrants. These data provide evidence of WNV transmission among birds in the Yucatán Peninsula.

Serologic evidence of West Nile virus infection in horses, Coahuila State, Mexico.

Serum samples were obtained from 24 horses in the State of Coahuila, Mexico, in December 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assay and confirmed by plaque reduction neutralization test in 15 (62.5%) horses. We report the first West Nile virus activity in northern Mexico.

Serologic evidence of West Nile virus infection in horses, Yucatan State, Mexico.

Serum samples were obtained from 252 horses in the State of Yucatan, Mexico, from July to October 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assays in three (1.2%) horses and confirmed by plaque reduction neutralization test. We report the first West Nile virus activity in the State of Yucatan.

Serologic evidence of West Nile Virus infection in birds, Tamaulipas State, México.

Following the introduction of West Nile virus (WNV) into North America in 1999, surveillance for WNV in migratory and resident birds was established in Tamaulipas State, northern México in December 2001. Overall, 796 birds representing 70 species and 10 orders were captured and assayed for antibodies to WNV. Nine birds had flavivirus-specific antibodies by epitope-blocking enzyme-linked immunosorbent assay; four were confirmed to have antibody to WNV by plaque reduction neutralization test. The WNV-infected birds were a house wren, mourning dove, verdin and Bewick's wren. The house wren is a migratory species; the other WNV-infected birds are presumably residents. The WNV-infected birds were all captured in March 2003. These data provide the first indirect evidence of WNV transmission among birds in northern México.

Evolutionary, ecological and taxonomic relationship between anboviruses of Florida, U.S.A. and Brazil

A few arbovirus and related viruses genotypic and phenotypic corollaries in both subtropical south Florida and tropical Brazil. Their occurrences in these areas may to intercontinental movement by circumstances or, most likely, to divergent virus evolution in divergently evolving hosts. It is counterintuitive that ecologic similarities and the presence of rodents and certain genera of mosquitoes alone would be sufficient to bring about convergent evolution and account for nucleotide similarities of such close order. Although relatively few, pairings such as these may indicate common ancestry and subsequent evolution

Foco permanente de fiebre amarilla en el Valle del Río Apurímac, Ayacucho, Perú, y primer aislamiento del virus de la fiebre amarilla en ese país / A continuing focus of yellow fever in the Apurimac River Valley, Ayacucho, Peru, and the first isolation of yellow fever virus in that country

En 1977 ocurrió en el sur de Perú un extenso brote de una enfermedad hemorrágica que correspondía a la fiebre amarilla, y a pesar de uma amplia campaña de vacunación hubieron brotes recurrentes en años posteriores. Las circunstacias epidemiológicas en que acaecieron estos brotes indican que un importante factor determinante fue el ingreso, repetido anualmente, de trabajadores migratorios susceptibles en un foco enzootico de esta enfermedad. Durante el estudio de dichos brotes los autores intentaron aislar el virus de la fiebre amarilla de muestras de sangre obtenidas de seis pacientes en 1977, cuatro en 1978 y cuatro en 1981, en la zona endémica. Con este propósito se inyectó sangre entera de los pacientes a ratones lactantes (por via intracraneal), y se inocularon ademas cultivos de celulas C6/36 (Aedes albopictus), ratones lactantes, LLCMK2 y Vero. Las cepas del virus aisladas de seis de estos pacientes se identificaron posteriormente como agentes causales de la fiebre amarilla, y es esta la primera vez que se logra aislar el virus en Perú

Relaciones antigenicas entre virus del complejo Tacaiuma del serogrupo Anopheles A (Bunyaviridae). / Antigenic relations between Tacaiuma complex viruses of the Anopheles A serogroup (Bunyaviridae)

En investigaciones de campo realizadas en forma independiente sobre la ecologia de los arbovirus en Arizona, EUA, y Sao Paulo Brasil, se aislaron dos virus del grupo Anopheles A. El virus aislado en Arizona (743-366), obtenido de mosquitos Anopheles freeborni, para el que se propone el nombre de virus Virgin River y el virus aislado en Sao Paulo (H-32580, obtenido de un ser humano) estaban vinculados serologicamente con el complejo Tacaiuma (TCM). Asimismo, se determino que los virus 743-366 y H-32580 son variantes de un subtipo del TCM (SPAr 2317). Sin embargo, es posible distinguir uno del otro. Se describen las circunstancias en que se hicieron estas observaciones y se resalta su significado en la epidemiologia, la genetica y la nomenclatura de la familia virica Bunyaviridae.

Durante pesquisas de campo não relacionadas sobre a ecologia dos arbovírus no Arizona, Estados Unidos, e em São Paulo, no Brasil, isolaram-se dois vírus dos Anopheles, grupo A. 0 vírus isolado no Arizona (743-366 tirado de mosquitos Anopheles freebornz) para o qual se propóe dar o nome de vírus Virgin River e o vírus isolado em São Paulo (H-32580 tirado de um ser humano), estavam serologicamente relacionados no âmbito do complex Tacaiuma (TCM). Determinou-se também que o 743-366 e o H- 32580 são variantes de um subtipo (SPAr2317) do TCM. Contudo, o 743-366 e o H-32580 diferenciam-se um do outro. Este artigo descreve as circunstancias em que se fueram essas observações e a sua significacão epidemiológica, terminológica e genética em relacão com a família dos Bunyaviridae.

Encefalitis equina del este en la Republica Dominicana, 1978. / Eastern equine encephalitis in Dominican Republic, 1978

En 1978, se presento en la Republica Dominicana un brote epizootico de EEE de proporciones aparentemente considerables. Este articulo describe las medidas tomadas para investigarlo y combatirlo

Encefalitis equina del este en la República Dominicana, 1978 / Eastern equine encephalitis in the Dominican Republic, 1978

En 1978, se presentó en la República Dominicana un brote epizoótico de EEE, de proporciones aparentemente considerables. Este artículo describe las medidas tomadas para investigarlo y combatirlo (AU)