Chikungunya Virus as Cause of Febrile Illness Outbreak, Chiapas, Mexico, 2014

Since chikungunya virus (CHIKV) was introduced into the Americas in 2013, its geographic distribution has rapidly expanded. Of 119 serum samples collected in 2014 from febrile patients in southern Mexico, 79% were positive for CHIKV or IgM against CHIKV. Sequencing results confirmed CHIKV strains closely related to Caribbean isolates

Chikungunya Virus Strains Show Lineage-Specific Variations in Virulence and Cross-Protective Ability in Murine and Nonhuman Primate Models

Chikungunya virus (CHIKV) is a reemerging arbovirus capable of causing explosive outbreaks of febrile illness, polyarthritis, and polyarthralgia, inflicting severe morbidity on affected populations. CHIKV can be genetically classified into 3 major lineages: West African (WA); East, Central, and South African (ECSA); Indian Ocean (IOL); and Asian. Additionally, the Indian Ocean (IOL) sublineage emerged within the ECSA clade and the Asian/American sublineage emerged within the Asian clade. While differences in epidemiological and pathological characteristics among outbreaks involving different CHIKV lineages and sublineages have been suggested, few targeted investigations comparing lineage virulence levels have been reported. We compared the virulence levels of CHIKV isolates representing all major lineages and sublineages in the type I interferon receptor-knockout A129 mouse model and found lineage-specific differences in virulence. We also evaluated the cross-protective efficacy of the IOL-derived, live-attenuated vaccine strain CHIKV/IRESv1 against the Asian/American CHIKV isolate YO123223 in both murine and nonhuman primate models, as well as the WA strain SH2830 in a murine model. The CHIKV/IRES vaccine provided protection both in mice and in nonhuman primate cohorts against Caribbean strain challenge and protected mice against WA challenge. Taken together, our data suggest that Asian/American CHIKV strains are less virulent than those in the Asian, ECSA, and WA lineages and that despite differences in virulence, IOL-based vaccine strains offer robust cross-protection against strains from other lineages. Further research is needed to elucidate the genetic basis for variation in CHIKV virulence in the A129 mouse model and to corroborate this variation with human pathogenicity

Phylodynamics of deer tick virus in North America

The burden of ticks and the pathogens they carry is increasing worldwide. Powassan virus (POWV; Flaviviridae: ), the only known North American tick-borne flavivirus, is of particular concern due to rising cases and the severe morbidity of POWV encephalitis. Here, we use a multifaceted approach to evaluate the emergence of the II POWV lineage, known as deer tick virus (DTV), in parts of North America where human cases occur. We detected DTV-positive ticks from eight of twenty locations in the Northeast USA with an average infection rate of 1.4 per cent. High-depth, whole-genome sequencing of eighty-four POWV and DTV samples allowed us to assess geographic and temporal phylodynamics. We observed both stable infection in the Northeast USA and patterns of geographic dispersal within and between regions. A Bayesian skyline analysis demonstrated DTV population expansion over the last 50 years. This is concordant with the documented expansion of tick populations and suggests an increasing risk of human exposure as the vector spreads. Finally, we isolated sixteen novel viruses in cell culture and demonstrated limited genetic change after passage, a valuable resource for future studies investigating this emerging virus

Clinical diagnoses made for CHIKF-positive and CHIKF-negative patients.

<p>Serum from patients visiting an emergency clinic in the DR was tested for CHIKV RNA and IgM, and results were retrospectively matched to initial diagnoses based on clinical presentation. The most common diagnosis for patients in both groups was undifferentiated febrile illness. Most notably, while CHIKF-positive (RNA-positive) patients (A) were more likely to be diagnosed with something other than CHIKF, no CHIKF-negative (RNA and IgM negative) patients (B) were misdiagnosed with CHIKF.</p

Demographic data for CHIKF(+) and CHIKF(-) patient serum samples collected from patients in La Romana, Dominican Republic July-August 2014, and associated relative risk.

<p>Demographic data for CHIKF(+) and CHIKF(-) patient serum samples collected from patients in La Romana, Dominican Republic July-August 2014, and associated relative risk.</p

Signs and symptoms recorded for CHIKF-positive (and CHIKF-negative) patients for whom complete blood counts were ordered between July 2014 and August 2014 at Hospital Buen Samaritano, La Romana, Dominican Republic.

<p>Signs and symptoms recorded for CHIKF-positive (and CHIKF-negative) patients for whom complete blood counts were ordered between July 2014 and August 2014 at Hospital Buen Samaritano, La Romana, Dominican Republic.</p

Distribution of total suspected cases of CHIKF reported in the Dominican Republic by province.

<p>A suspected case was defined by the presence of sudden fever and arthralgia. The color scheme classifies provinces by number of total suspected CHIKF cases, determined by summing the number of cases reported in MSP DIGEPI weekly bulletins and Chikungunya Outbreak Bulletins for each epidemiological weeks between February 16, 2014 and June 6, 2015. No exact case numbers were reported to MSP DIGEPI for provinces shaded in white. Number 32, Distrito Nacional, represents the national district, which does not pertain to a province. The city of La Romana and the port of Bajos de Haina, where the outbreak is suspected to have started, are highlighted in red. Map created using Epi Info^TM 7.1.5 software licensed by the Centers for Disease Control and Prevention (<a href="http://wwwn.cdc.gov/epiinfo/7/" target="_blank">http://wwwn.cdc.gov/epiinfo/7/</a>). MSP DIGEPI weekly bulletins publicly available through Minesterio de Salud Publica (<a href="http://digepisalud.gob.do/" target="_blank">http://digepisalud.gob.do/</a>).</p