The Mayaro virus is a lesser-known illness transmitted by mosquitoes, primarily affecting people in tropical regions of the Americas. It often causes an acute, self-limited disease, sometimes referred to as Mayaro fever or jungle flu.
Understanding Mayaro Virus
The Mayaro virus (MAYV) is an arbovirus. It belongs to the Alphavirus genus within the Togaviridae family. This classification places it in the same group as other well-known viruses like Chikungunya virus (CHIKV), with which it shares structural similarities and some common antigenic sites, leading to potential cross-reactivity in tests. The virus was first identified in 1954 in Mayaro County, Trinidad, from the blood samples of forest workers experiencing fever. Since its discovery, Mayaro virus has been recognized primarily in tropical regions of South and Central America, including Brazil, Bolivia, Ecuador, French Guiana, Peru, Suriname, and Venezuela.
How Mayaro Virus Spreads
The main vectors for this virus are mosquitoes of the Haemagogus species, which typically inhabit forest environments and are known for their diurnal biting habits. These mosquitoes acquire the virus by feeding on infected non-human primates, such as monkeys and marmosets, which serve as natural reservoirs for the virus in the sylvatic (forest) cycle. Birds, rodents, marsupials, horses, and reptiles have also shown evidence of infection, suggesting their possible involvement in the transmission cycle.
While the primary transmission occurs in forested areas, there is concern about the potential for spread into urban environments. Studies have shown that Aedes aegypti and Aedes albopictus mosquitoes, common in urban settings, can also transmit Mayaro virus. This raises the possibility of human-to-mosquito-to-human transmission cycles in more populated areas, especially given the widespread distribution of these Aedes species. Cases of Mayaro virus have been reported in travelers returning from endemic areas to regions like North America and Europe, highlighting the risk of international spread.
Symptoms of Mayaro Virus Infection
The incubation period for Mayaro virus disease typically ranges from 1 to 14 days after a mosquito bite. Following this period, the illness usually begins suddenly with a high fever. Common symptoms include headache, muscle aches (myalgia), chills, and a rash.
A distinguishing feature of Mayaro virus infection is the often severe and prolonged joint pain, known as arthralgia, which can affect fingers, wrists, ankles, and toes, and sometimes elbows and knees. This joint pain can be debilitating and may persist for weeks or even months, in some cases up to a year, even after other symptoms resolve. Other less common symptoms that may occur include eye pain, swollen lymph nodes, abdominal pain, nausea, vomiting, and dizziness. The symptoms of Mayaro virus infection can be similar to those of other arboviral diseases like dengue, chikungunya, and Zika, making clinical differentiation challenging.
Diagnosing and Treating Mayaro Virus
Diagnosing Mayaro virus infection involves laboratory methods to confirm the presence of the virus or antibodies against it. During the acute phase of illness, typically within the first 3 to 5 days of symptom onset, molecular tests like Reverse Transcription Polymerase Chain Reaction (RT-PCR) are used to detect viral RNA in blood samples. A positive RT-PCR result confirms the diagnosis.
However, the viremia (virus in the blood) can be low, which might result in high cycle threshold (Ct) values in real-time RT-PCR assays, requiring careful interpretation. For later stages of infection, or after the initial viremic phase, serological tests such as Enzyme-Linked Immunosorbent Assay (ELISA) are employed to detect antibodies, specifically IgM and IgG, in the patient’s blood. The presence of IgM antibodies suggests a recent infection.
There is currently no specific antiviral treatment available for Mayaro virus infection. Management focuses on supportive care to alleviate symptoms, which includes rest, adequate fluid intake, and pain relief medication. Patients should avoid aspirin or nonsteroidal anti-inflammatory drugs if dengue is suspected or has not been ruled out. In instances of severe symptoms, hospitalization may be necessary to provide supportive care such as intravenous fluids and pain management.
Protecting Against Mayaro Virus
Protecting against Mayaro virus infection primarily involves preventing mosquito bites, as there is no vaccine available for human use. Individuals in or traveling to areas where the virus is present, including parts of South America, Central America, and the Caribbean, should take personal protective measures. These include:
Wearing long-sleeved shirts and long pants outdoors.
Using insect repellents containing active ingredients such as DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535 on exposed skin.
Treating clothing and gear with 0.5% permethrin.
For those staying in lodging without air conditioning or screens, using mosquito nets around beds.
Community-level prevention strategies involve mosquito control efforts in endemic regions to reduce mosquito populations.