What Is the Mayaro Virus?

Mayaro virus may be more common than we thought

Mosquitoes bite. It's usually just a nuisace. But with each bite, it might be more. There's a small chance they may be spreading disease, and although that seems scary, remember that just having mosquitoes and viruses around is not enough. It has to be the right virus for the right mosquito in the right place. Mosquitoes can create a bit of a problem if the right viruses and other pathogens are present.

The right virus, the right mosquito, and the right place seem to be lining up more and more. We've been seeing more mosquito borne viral outbreaks. This has meant not just Zika, but also ChikungunyaDengue, and yellow fever. These viruses appeared suddenly where they weren't quite expected, especially in the Americas, but also in Asia and Africa.

Could Mayaro Virus the New Bug on the Block?

A lab sample from a boy with a fever in Haiti in 2015 was shown to be positive for Mayaro. The virus has never been seen in Haiti before. All prior cases were seen in South America.

It's possible that the virus has been there all along, just not identified. The virus likely first came to South America from Africa a few hundred years ago. Without the lab capacity to test for this virus, it may have been that other cases were assumed to be Dengue or never diagnosed at all.

The virus seen has a different ancestry than many other recent strains seen in South America.

It does have similar ancestry to strains found in Brazil over the past 50 years.

With hindsight, it was seen that Zika had been in Haiti before it had been identified in Brazil (though it may have been in Brazil earlier as well). With Zika though, the virus had come from the South Pacific. But it still might be that the virus has been in Haiti longer than we knew.

There's no reason to believe that Mayaro will suddenly spread, but it will be good to keep watching for viruses.

Symptoms of Mayaro Virus Disease

The disease caused by Mayaro virus (MAYV) starts suddenly and usually lasts three to five days. This illness can involve a fever, joint aches, muscle pains, headache, eye pain (particularly behind the eyes), rash, as well as nausea, vomiting, and diarrhea. Rarely, bleeding symptoms have occurred.

The infection is usually short lived, but it can lead to long-lasting joint pains. This can be a real problem for those affected by long-lasting or recurrent pain. These pains may especially be in the ankles, knees, or hands and can be incapacitating, making it difficult to walk or to write. It is, however, usually self-limited. Most people are just fine afterwards.

There hasn't been any reports of problems during pregnancy, but the virus has not been studied as well as other viruses because it has been rare and found in remote areas.

Where Can Mayaro Virus Spread?

That depends on a lot of things.

A lot of it depends on what mosquitoes are present and whether these mosquitoes can spread this virus. Not all mosquitoes spread all mosquito-borne viruses. 

The mosquito often associated with the Mayaro virus is largely found in South America (Haemagogus janthinomys). This was thought to be part of the reason the virus was where it was - and not elsewhere. 

However, there are a number of different mosquitoes that are associated (including Mansonia venezuelensis and some Culex mosquitoes).

Even more importantly, for all of us living far from the Amazon, the virus may be able to spread through Aedes mosquitoes (i.e. like Aedes aegypti). This is the same mosquito that has spread Zika, Dengue, and Chikungunya. Aedes aegypti is found in much of the Americas, Asia, and Africa. The mosquito can be found in some states in the southern part of the US.

Where Has Mayaro Been Found?

The virus usually spreads in forests.

It was first found in the 1950's among workers in the forest in Trinidad. There is a town and county in Trinidad called Mayaro, which was the area where the Mayaro virus was first identified. Since then people in small outbreaks and returning travelers have been found to have the virus or antibodies to the virus. In particular, transmission has been recorded in Brazil, Venezuela, Peru, French Guyana, Ecuador, Bolivia, Suriname, as well as Trinidad and Tobago and now Haiti.

Antibodies have been found as far north as Panama, Costa Rica, Guatemala, and Mexico. It may be that this virus has been more widespread than we knew.

What Diseases Are Like Mayaro Virus?

Mayaro is a lot like Dengue and Chikungunya, as well as Zika. The rash and joint pains can seem pretty similar in all of these diseases and so the infection may be misdiagnosed.

How Do You Test for Mayaro Virus?

There are blood tests for Mayaro virus. These look for antibodies, as well as directly for the virus. This can be done at specialty referral labs, like the CDC. This is not a test that can be run at a local clinic or hospital. Moreover, clinical exam and basic lab tests will make the virus seem like it is dengue. Lab tests often show low platelets and a low white blood cell count, like in Dengue.

Is There a Vaccine?

Not yet. There is however work on a vaccine, much like there is work on a Zika vaccine.

How Is Mayaro Classified?

It's an Alphavirus, which belongs to the Togaviridae family of viruses. Other Alphaviruses include: Chikungunya virus, Eastern equine encephalitis virus, O’Nyong Nyong virus, Ross River virus, and Barmah Forest virus. There are many other Alphaviruses that infect humans, mammals (including horses), and all sorts of animals, such as many birds.

Why Are We Seeing More Viruses?

A big piece of this is globalization.

Travel, both local and international, moves bugs from where they're common now to where they've never been seen before. This means that an infection that's common but not overwhelming may, when it's taken somewhere new, infect everyone at once.

Before, most people would get the infection when they were kids (because it was so common, it was hard to make it to adulthood without getting it). However, once an infection is exported somewhere totally new, it might suddenly spread to everyone all at once as no one has had it before. In this new place there's no herd immunity; no one is immune and everyone is susceptible all at once, not just a few kids getting randomly sick at a time.

But there's more than just globalization and travel. Diseases have been spreading now for a variety of reasons:

  • With warm climates supporting mosquito spread, Climate Change may also speeds up the spread of disease.
  • More people living in crowded cities also means that Urbanization amplifies the spread of new viruses.
  • More work in rural areas—such as mining, farming, or settlements—can also introduce new viruses from forests into cities.
  • Agriculture, especially the movement of livestock or the inadvertent transport of bugs, can help introduce infections as well.
  • Health facilities may also amplify some infections if proper precautions aren't taken.​

Combatting the Viruses

When bugs travel, we learn more things about them.

What might seem like a mild infection in one place is found to carry more risks somewhere else. Sometimes this is just because surveillance and healthcare are different in different places. But it's also because infections can affect some people differently.

An infection that's common and just affects children may be very different if it's infecting everyone at once. Some infections are very different in children than in adults, especially pregnant women as well as the infants then born. This can result in outcomes rarely if ever seen before, like microcephaly, being noticed. Zika isn't alone in this. The same thing would have happened if say chickenpox were newly introduced and instead of only infecting children, also infected pregnant women whose children then had microcephaly or other problems. So infections we knew in one place may not be the same somewhere else, but as we learn more about them, we can better tackle them.

Sources:

Mayaro Virus in Child with Acute Febrile Illness. Haiti. 2015.

Mayaro Virus Disease: An Emerging Mosquito-Borne Zoonosis in Tropical South America.

Kanya C, et al. Experimental Transmission of Mayaro Virus by Aedes aegypti. Am J Trop Med Hyg. 2011 Oct 1; 85(4): 750–757.

Mayaro Virus: A New Human Disease Agent: II. Isolation from Blood of Patients in Trinidad.
http://www.ajtmh.org/content/6/6/1012.long 

Mourão M, et al. Mayaro Fever in the City of Manaus. Brazil. 2007–2008. Vector Borne Zoonotic Dis. 2012 Jan; 12(1) 42-46.

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