We studied molecular evolution of the mosquito-borne alphavirus Highlands J (HJ) virus by sequencing PCR products generated from 19 strains isolated between 1952 and 1994. Sequences of 1200 nucleotides including portions of the E1 gene and the 3' untranslated region revealed a relatively slow evolutionary rate estimated at 0.9-1.6 x 10(-4) substitutions per nucleotide per year. Phylogenetic trees indicated that all HJ viruses descended from a common ancestor and suggested the presence of one dominant lineage in North America. However, two or more minor lineages probably circulated simultaneously for periods of years to a few decades. Strains isolated from a horse suffering encephalitis, and implicated in a recent turkey outbreak, were not phylogenetically distinct from strains isolated in other locations during the same time periods. Our findings are remarkably similar to those we obtained previously for another North American alphavirus, eastern equine encephalomyelitis virus, with which Highlands J shares primary mosquito and avian hosts, geographical distribution, and ecology. These results support the hypotheses that the duration of the transmission season affects arboviral evolutionary rates and vertebrate host mobility influences genetic diversity.

The transcontinental spread of multidrug-resistant (MDR) tuberculosis is poorly characterized in molecular epidemiologic studies. We used genomic sequencing to understand the establishment and dispersion of MDR Mycobacterium tuberculosis within a group of immigrants to the United States. We used a genomic epidemiology approach to study a genotypically matched (by spoligotype, IS6110 restriction fragment length polymorphism, and mycobacterial interspersed repetitive units-variable number of tandem repeat signature) lineage 2/Beijing MDR strain implicated in an outbreak of tuberculosis among refugees in Thailand and consecutive cases within California. All 46 MDR M. tuberculosis genomes from both Thailand and California were highly related, with a median difference of 10 single-nucleotide polymorphisms (SNPs). The Wat Tham Krabok (WTK) strain is a new sequence type distinguished from all known Beijing strains by 55 SNPs and a genomic deletion (Rv1267c) associated with increased fitness. Sequence data revealed a highly prevalent MDR strain that included several closely related but distinct allelic variants within Thailand, rather than the occurrence of a single outbreak. In California, sequencing data supported multiple independent introductions of WTK with subsequent transmission and reactivation within the state, as well as a potential super spreader with a prolonged infectious period. Twenty-seven drug resistance-conferring mutations and 4 putative compensatory mutations were found within WTK strains. Genomic sequencing has substantial epidemiologic value in both low- and high-burden settings in understanding transmission chains of highly prevalent MDR strains.

Background/Aims: Few studies have compared population-based tuberculosis (TB) incidence rates by end-stage renal disease (ESRD) status. No studies have compared TB genotypes by ESRD status to determine whether TB disease resulted from recent transmission or reactivation of latent TB infection (LTBI). We calculated TB incidence rates and compared demographic and clinical characteristics and genotypes among TB cases by ESRD status. Methods: This analysis was based on prospective surveillance for TB cases during 2010 in California. Clustered genotype was defined as ≥2 culture-positive TB cases with matching genotypes in the same county. The χ² or Wilcoxon rank-sum test was used to compare variables. Results: During 2010, 83 TB cases with ESRD and 2,244 cases without ESRD were reported in California; TB incidence rates were 110.3/100,000 and 6.0/100,000, respectively. ESRD case patients versus patients without ESRD were more likely to be older (median age 66 vs. 49 years; p < 0.001), foreign-born persons who had arrived in the USA >5 years before TB diagnosis (97 vs. 75%; p < 0.001) and dead at TB diagnosis (7 vs. 2%; p = 0.01). ESRD patients were less likely to have a positive tuberculin skin test (50 vs. 80%; p < 0.001), positive acid-fast bacilli sputum smears (33 vs. 53%; p = 0.01) and cavities on chest radiography (6 vs. 21%; p = 0.01). No differences in proportions of clustered TB genotypes were detected (20 vs. 23%; p = 0.54). Conclusions: Rates of TB are 18 times higher in California's ESRD population, and TB disease likely occurred due to LTBI reactivation because few patients had clustered genotypes. Efforts to prevent TB among ESRD patients may require the use of newer diagnostic tests and promotion of LTBI treatment.

Vesicular stomatitis virus (VSV) populations were repeatedly passaged in L-929 cells treated with alpha interferon (IFN-␣) at levels of 25 U/ml. This IFN-␣ concentration induced a 99.9% inhibition of viral yield in standard infections. Analysis of viral fitness (overall replicative ability measured in direct competition with a reference wild-type VSV) after 21 passages in IFN-treated cells showed only a limited increase or no increase in fitness, compared with the greater increase upon parallel passage in cells not treated with IFN-␣. However, this limited increase in fitness was more pronounced when competition assays were carried out with IFN-␣treated cells, suggesting the selection of VSV populations with a low level of resistance to IFN-␣. Thus, despite the extensively documented capacity of VSV to adapt to changing environments, the antiviral state induced by IFN-␣ imposes adaptive constraints on VSV which are not readily overcome.