BACKGROUND The eastern equine encephalitis (EEE) and Venezuelan equine encephalitis (VEE) viruses are pathogens that infect humans and horses in the Americas. Outbreaks of neurologic disease in humans and horses were reported in Panama from May through early August 2010. METHODS We performed antibody assays and tests to detect viral RNA and isolate the viruses in serum samples from hospitalized patients. Additional cases were identified with enhanced surveillance. RESULTS A total of 19 patients were hospitalized for encephalitis. Among them, 7 had confirmed EEE, 3 had VEE, and 1 was infected with both viruses; 3 patients died, 1 of whom had confirmed VEE. The clinical findings for patients with EEE included brain lesions, seizures that evolved to status epilepticus, and neurologic sequelae. An additional 99 suspected or probable cases of alphavirus infection were detected during active surveillance. In total, 13 cases were confirmed as EEE, along with 11 cases of VEE and 1 case of dual infection. A total of 50 cases in horses were confirmed as EEE and 8 as VEE; mixed etiologic factors were associated with 11 cases in horses. Phylogenetic analyses of isolates from 2 cases of equine infection with the EEE virus and 1 case of human infection with the VEE virus indicated that the viruses were of enzootic lineages previously identified in Panama rather than new introductions. CONCLUSIONS Cases of EEE in humans in Latin America may be the result of ecologic changes that increased human contact with enzootic transmission cycles, genetic changes in EEE viral strains that resulted in increased human virulence, or an altered host range. (Funded by the National Institutes of Health and the Secretaría Nacional de Ciencia, Tecnología e Innovación, Panama.)

Dengue virus (DENV) is the most prevalent arbovirus in terms of human public health importance globally. In addition to DENV epidemiological surveillance, genomic surveillance may help investigators understand the epidemiological dynamics, geographic distribution, and temporal patterns of DENV circulation. Herein, we aimed to reconstruct the molecular epidemiology and phylogeny of DENV in Panama to connect the epidemiological history of DENV dispersal and circulation in Latin America. We retrospectively analyzed the epidemiological data obtained during 25 years of DENV surveillance in Panama. DENV was reintroduced in Panama in 1993 after a 35 year absence of autochthonous transmission. The increase in the number of total dengue cases has been accompanied by an increase in severe and fatal cases, with the highest case fatality rate recorded in 2011. All four serotypes were detected in Panama, which is characterized by serotype replacement and/or co-circulation of multiple serotypes. Phylogenetic analysis of datasets collected from envelope (E) gene sequences obtained from viruses isolated from human sera demonstrated that circulating viruses were highly diverse and clustered in distinct clades, with co-circulation of clades from the same genotype. Our analyses also suggest that Panamanian strains were related to viruses from different regions of the Americas, suggesting a continuous exchange of viruses within the Americas.

Rubella virus (RUBV) usually causes a mild exanthematous disease that is frequently accompanied by adenopathy and occasionally by arthralgia. Complications of this infection are rare and include encephalopathy and thrombocytopenia. However, the most severe consequence of this virus is its teratogenicity. It can cause congenital rubella syndrome (CRS) when it occurs in pregnant women, particularly during the first trimester of pregnancy (10).The direct detection of RUBV RNA in clinical specimens, in addition to the detection of RUBV-specific immunoglobulin M, is a critical factor in the early laboratory diagnosis of recent or congenital infection (18,27). Currently, the European region of the World Health Organization (WHO) aims to eliminate not only measles but also rubella and to reduce the incidence of CRS to less than one case per 100,000 live births by 2010 (38, 39). For this purpose, epidemiological surveillance based on the laboratory diagnosis of each suspected case and the characterization of the genotype of the circulating strains are included in the WHO's recommendations. In the most recent WHO update, the standard nomenclature for the classification and designation of wild-type RUBV strains recognizes nine definitive and four provisional genotypes (40), expanding the nomenclature established in 2005 (37), which was based on 739 nucleotides (nt) (nt 8731 to 9469) from the E1 gene sequence. This sequence encodes amino acids (aa) 159 to 404 (of the 481 aa) of the E1 glycoprotein. Although our knowledge of the geographic distribution of RUBV genotypes has grown substantially since 2003, the genotypes present in many countries and regions remain unknown (9), even though rubella is still recognized as a globally important disease in a general public health context (41). RUBV is considered monotypic with cross-neutralization among different genotypes.In Spain, monovalent RUBV vaccine was introduced in the late 1970s, when it was administered in schools to 11-year-old girls (1). In 1981, one dose of the measles-mumps-rubella combined vaccine was introduced in the regular immunization schedule at the age of 15 months for all children. In 1996, a second dose at 11 years of age was introduced (5). In 1999, this second dose was given to 4-year-old children (3). Currently, the seroprevalence of RUBV in the community of Madrid exceeds 95% in all age groups and reaches 98.6% among women of childbearing age (16 to 45 years) (4). Nevertheless, the pattern is very different in other regions around the world and RUBV infection remains endemic in many areas, such as Latin America (15). The rubella vaccine was only introduced in Latin American countries in the late 1990s, so that many adult immigrants to Spain are not immunized. These circumstances led to a small outbreak in Madrid in 2003 (31) and a larger one in 2004 and 2005 (2, 27) among Latin American immigrants. The main aim of this study was to characterize the RUBV strain involved in the latter outbreak, which represents the first data concerning RUBV genotypes i...