Reconstructing Mayaro virus circulation in French Guiana shows frequent spillovers.

Characterizing the circulation of Mayaro virus (MAYV), an emerging arbovirus threat, is essential for risk assessment but challenging due to cross-reactivity with other alphaviruses such as chikungunya virus (CHIKV). Here, we develop an analytical framework to jointly assess MAYV epidemiology and the extent of cross-reactivity with CHIKV from serological data collected throughout French Guiana (N = 2697). We find strong evidence of an important sylvatic cycle for MAYV with most infections occurring near the natural reservoir in rural areas and in individuals more likely to go to the forest (i.e., adult males) and with seroprevalences of up to 18% in some areas. These findings highlight the need to strengthen MAYV surveillance in the region and showcase how modeling can improve interpretation of cross-reacting assays.

Madariaga Virus: Identification of a Lineage III Strain in a Venezuelan Child With Acute Undifferentiated Febrile Illness, in the Setting of a Possible Equine Epizootic.

We report identification of Madariaga virus (MADV) in plasma and urine samples from a child with acute undifferentiated febrile illness in Venezuela. Our data document the occurrence of milder MADV infections (ie, without encephalitis), with a symptom complex that resembles that seen with other arboviral infections, including dengue and zika.

Seroepidemiology of selected alphaviruses and flaviviruses in bats in Trinidad.

A serosurvey of antibodies against selected flaviviruses and alphaviruses in 384 bats (representing 10 genera and 14 species) was conducted in the Caribbean island of Trinidad. Sera were analysed using epitope-blocking enzyme-linked immunosorbent assays (ELISAs) specific for antibodies against West Nile virus (WNV), Venezuelan equine encephalitis virus (VEEV) and eastern equine encephalitis virus (EEEV), all of which are zoonotic viruses of public health significance in the region. Overall, the ELISAs resulted in the detection of VEEV-specific antibodies in 11 (2.9%) of 384 bats. Antibodies to WNV and EEEV were not detected in any sera. Of the 384 sera, 308 were also screened using hemagglutination inhibition assay (HIA) for antibodies to the aforementioned viruses as well as St. Louis encephalitis virus (SLEV; which also causes epidemic disease in humans), Rio Bravo virus (RBV), Tamana bat virus (TABV) and western equine encephalitis virus (WEEV). Using this approach, antibodies to TABV and RBV were detected in 47 (15.3%) and 3 (1.0%) bats, respectively. HIA results also suggest the presence of antibodies to an undetermined flavivirus(es) in 8 (2.6%) bats. Seropositivity for TABV was significantly (P<0.05; χ2) associated with bat species, location and feeding preference, and for VEEV with roost type and location. Differences in prevalence rates between urban and rural locations were statistically significant (P<0.05; χ2) for TABV only. None of the aforementioned factors was significantly associated with RBV seropositivity rates.

Mayaro fever in the city of Manaus, Brazil, 2007-2008.

Mayaro Alphavirus is an arbovirus that causes outbreaks of acute febrile illness in the Amazon region of South America. We show here the cases of Mayaro fever that occurred in 2007-2008, in Manaus, a large city and capital of the Amazonas State, in Western Brazilian Amazon. IgM antibodies to Mayaro virus (MAYV) were detected by an enzyme immunoassay using infected cell cultures as antigen in the sera of 33 patients from both genera and 6-65 years old. MAYV genome was also detected by RT-PCR in the blood of 1/33 of these patients. The patients presented mainly with headache, arthralgia, myalgia, ocular pain, and rash. These cases of Mayaro fever are likely to represent the tip of an iceberg, and probably a much greater number of cases occurred in Manaus in the study period.