Mayaro virus has a structure similar to other alphaviruses. It is an enveloped virus and has an icosahedral capsid with a diameter of 70 nm. The virus genome is composed of a linear, positive-sense, single-stranded RNA with 11,429 nucleotides, excluding the 5’ cap nucleotide and 3’ poly(A) tail.[2][3]
The MAYV RNA genome contains the 5' untranslated region, 3' noncoding region, and two open reading frames (ORFs). The 5' proximal and 3' proximal ORFs are separated by a short, noncoding sequence and represent two-thirds and one-third of the genomic RNA, respectively. The 5’-proximal ORF codes for a polyprotein that after cleavage forms nonstructural proteins (nsP1, nsP2, nsP3, nsP4) and the 3’-proximal ORF with a 26S promoter codes for a polyprotein that is cleaved into structural proteins to generate capsid proteins and envelope surface glycoproteins (E1, E2, E3, C, 6K).[2][4][5][6]
The nonstructural proteins (nsP) play different functions in the virus cycle. The nsP1 is an mRNA-capping enzyme, nsP2 has protease activity, and nsP4 is a RNA-direct RNA polymerase. The structural polyprotein is cleaved into six chains: capsid protein (C), p62, E3 protein or spike glycoprotein E3, E2 envelope glycoprotein or spike glycoprotein E2, 6K protein, and E1 envelope glycoprotein known also as spike glycoprotein E1.[7][8] The envelope lipid component is critical for virus particle stability and infectivity in mammalian cells[9] Once the virus enters into the host cell, the genomic RNA is released into the cytoplasm, where the two ORFs are translated into proteins and the synthesis of negative-stranded RNA starts. A consecutive synthesis of positive-stranded RNA takes place.[8]
The MAYV sequences analysis showed two genotypes (D and L). The amplicon used for phylogenetic analysis includes E1 and E2 glycoprotein genes and the 3' NCR. The genotype D is distributed in Trinidad, Brazil, French Guiana, Surinam, Peru, and Bolivia, while the genotype L is limited to the north-central region of Brazil.[10]
Diagnosis
The MAYV infection is characterized by fever, headache, myalgia, rash, prominent pain in the large joints, and association with rheumatic disease,[11][12] but these signs and symptoms are unspecific to distinguish from other arboviruses. The MAYV infection can be confirmed by laboratory testing such as virus isolation, RT-PCR, and serology. The virus isolation in cell culture is effective during viremia. RT-PCR helps to identify virus. Serology tests detect antibodies like IgM and the most common assay is IgM-capture enzyme-linked immunosorbant assays (ELISA). This test usually requires a consecutive retest to confirm increasing titers.[13][14] While the IgG detection is applied for epidemiology studies.[15]
Epidemiology
The virus's transmission cycle in the wild is similar to the continuous
sylvatic cycle of
yellow fever, and is believed to involve wild
primates (
monkeys) as the
natural reservoir and the tree canopy-dwelling Haemagogus species
mosquito as the
vector.[1] Human infections are strongly associated with exposure to humid tropical forest environments.
Chikungunya virus is closely related, producing a nearly indistinguishable, highly debilitating arthralgic disease.[citation needed]
On February 19, 2011, a Portuguese-language news source reported on a recent survey that revealed Mayaro virus activity in
Manaus,
Amazonas State,
Brazil.[16] The survey studied blood samples from 600 residents of Manaus who had experienced a high fever; Mayaro virus was identified in 33 cases. Four of the cases experienced mild hemorrhagic (bleeding) symptoms, which had not previously been described in Mayaro virus disease. The report stated that this outbreak is the first detected in a metropolitan setting, and expressed concern that the disease might be adapting to urban species of mosquito vectors, which would make it a risk for spreading within the country.[citation needed]
A study published in 1991 demonstrated that a colonized strain of Brazilian Aedes albopictus was capable of acquiring MAYV from infected hamsters and subsequently transmitting it,[17] and another study demonstrated that A. aegypti can transmit MAYV, supporting the possibility of wider transmission of Mayaro virus disease in urban settings.[18]
In January 2010, a French tourist developed high-grade fever and severe joint pain manifestations following a 15-day trip in the
Amazon basin, Brazil, and was diagnosed with MAYV infection in France. This case is the first reported in a traveler returning from an endemic South American country to Europe.[21] Mayaro virus disease has also been transported into the
United States by two visitors infected in eastern
Peru[22] and into the Netherlands by a couple infected while vacationing in
Suriname.[23]
The first outbreak of Mayaro virus disease in humans in
Venezuela was reported in early June 2010, with 69 cases diagnosed in
Ospino,
Portuguesa state, and an additional two in
San Fernando de Apure,
Apure state, on 7 June 2010, for a total of 71 reported cases as of 8 June.[24]
A single case of Mayaro virus in a child in
Haiti in 2015 has been confirmed.[25]
In 2019, cases were reported in Peru and Ecuador.[26]
^Smith GC, Francy DB (1991). "Laboratory studies of a Brazilian strain of Aedes albopictus as a potential vector of Mayaro and Oropouche viruses". Journal of the American Mosquito Control Association. 7 (1): 89–93.
PMID1646286.
^
abMarco Brustolin, Sujit Pujhari, Cory A. Henderson, and Jason L. Rasgon. 2018. Anopheles mosquitoes may drive invasion and transmission of Mayaro virus across geographically diverse regions. PLOS Neglected Tropical Diseases 12(11): e0006895,
https://doi.org/10.1371/journal.pntd.0006895, last accessed 30 Nov 2018.
^Tesh RB, Watts DM, Russell KL, Damodaran C, Calampa C, Cabezas C, Ramirez G, Vasquez B, Hayes CG, Rossi CA, Powers AM, Hice CL, Chandler LJ, Cropp BC, Karabatsos N, Roehrig JT, Gubler DJ (1999). "Mayaro virus disease: an emerging mosquito-borne zoonosis in tropical South America". Clinical Infectious Diseases. 28 (1): 67–73.
doi:
10.1086/515070.
PMID10028074.
S2CID17427509.
^Hassing RJ, Leparc-Goffart I, Blank SN, Thevarayan S, Tolou H, van Doornum G, van Genderen PJ (2010). "Imported Mayaro virus infection in the Netherlands". The Journal of Infection. 61 (4): 343–5.
doi:
10.1016/j.jinf.2010.06.009.
PMID20600300.