**2.1 Mayaro (MAYV)**

MAYV, an enzootic virus [44, 45], is an alphavirus that shares epidemiological features with YFV, having sylvatic cycles involving animal reservoirs and with sylvatic and urban mosquito vectors. Clinically, MAYV shares characteristics with its genus and family. It is an arthritogenic alphavirus, as occurs with CHIKV, able to generate immune-mediated chronic disease [46, 47] but overlaps in symptoms during the acute phase with other arboviruses [48]. A few years ago, the ChikDenMaZika syndrome was proposed as a mnemotechnic rule to keep in mind Mayaro and other more frequently observed arboviruses, such as CHIKV, DENV, and ZIKV [48]. That would help decrease the negligence of Mayaro, to be considered in the differential diagnosis of febrile syndrome in the tropics or possibly caused by an arbovirus. MAYV is more frequently detected in other countries, in addition to Trinidad and Tobago, Brazil, and Peru. It has also been identified in Panama, French Guiana, Colombia, Argentina, Venezuela, and Paraguay [49, 50]. Studies have reported MAYV positivity in wild mammals, birds, or reptiles, as well as in domestic animals. Also, 12 orders of wildcaught vertebrates, most frequently in Charadriiformes and primate orders, have been identified with MAYV. This alphavirus has been detected in wild-caught mosquito genera, including *Haemagogus*, *Aedes*, *Culex*, *Psorophora*, *Coquillettidia*, and *Sabethes* [49]. Although MAYV has been identified in urban vectors, there is no evidence of sustained urban transmission. MAYV's enzootic cycle could become established in forested areas within cities, similar to the yellow fever virus [51]. Arboviruses in mosquito body pools sampled during the rainy season of 2018 in 21 bird-watching points of Cuiabá and Varzea Grande, south central Mato Grosso, Brazil, highlights the possibility of MAYV detection in urban areas of Latin America [52]. An investigation of arboviruses in patients with acute febrile illness (n=453) for less than 5 days in Mato Grosso state during the period of ZIKV and CHIKV dissemination in Brazil found multiple other neglected arboviruses [53]. Alphaviruses were detected in 2 (0.4%) patients infected with CHIKV genotype ECSA, 1 (0.2%) with Madariaga (EEEV) lineage III, and 34 (7.5%) with Mayaro (MAYV) genotype L. Four (11.4%) patients presented dual infections with DENV-1/ZIKV, DENV-1/DENV4, DENV-4/MAYV, and ZIKV/MAYV. The majority—13/34 positive for MAYV, one for Madariaga virus—are residents in Várzea Grande, the metropolitan region of Cuiabá, the capital of Mato Grosso [53]. Up to June 2015, only 121 articles were published in PubMed-indexed journals, based on a bibliometric analysis [47]. After 7 years, only 230 additional papers have been published on MAYV (**Figure 3**).

In countries, such as Peru, MAYV has become more critical in epidemiological terms; even MAYV is under surveillance in that country (**Figure 4**). Although that, there is still a lack of research from that country in MAYV (only 28 articles, <8% of the total on MAYV in PubMed). Especially in jungle areas in the country's north and south border with Brazil, Peru has endemic areas where MAYV and other arboviruses cause infection.

During 2017–2020, a total of 36 cases were reported by Peru (**Table 1**), most of them (29, 81%) in 2017 and predominantly in the Madre de Dios department (16, 44%) that year (**Table 1**). At least seven departments of Peru, from a total of 24, reported at least one case of MAYV during that period.

## **Figure 4.**

*Geographical distribution of ZIKV, CHIKV, and MAYV in Peru, 2020. (Modified from https://www.dge.gob.pe/ epipublic/uploads/boletin/boletin\_202043.pdf).*
