RIO – Scientists from the Federal University of Rio de Janeiro (
) discovered a new virus circulating in the state of Rio.
, a cousin of the
and that causes disease with symptoms similar to this, as intense and disabling
in the joints, which last for months.
Since 2015, researchers have warned of the risk that mayaro, a wild Amazon virus, establish itself in large cities in the Southeast. The newly completed study shows that the worst has happened. Mayaro is among us, says Rodrigo Brindeiro, one of the authors of the discovery and coordinator of the Network
of UFRJ. As in the case of chicungunha, there is no vaccine or treatment. Only the symptoms are treated in a non-specific way.
The Mayaro has been known since the 1950s in South and Central America. In Brazil, it has caused isolated outbreaks in the northern and midwestern states. Transmitted by
, the same as wild yellow fever, he gave signs that he had begun to adapt to the cities.
Laboratory tests have shown that it can be transmitted both by
how much by
), which potentiates the risk of an epidemic, says Amílcar Tanuri, coordinator of the Laboratory of Molecular Virology at UFRJ, where the study was carried out.
The arrival of mayaro increases the difficulty of controlling mosquito-borne diseases in a country plunged into a sanitary abyss. In 2015, came the zika epidemic, with microcephaly. Chicungunha, introduced in 2014, expanded around the same time. The beginning of 2017 was marked by the return of the yellow fever to the Southeast, with the largest epidemic of the wild form already registered in the Americas.
This year began with an outbreak of dengue cases (an increase of 339.9% over the same period of 2018), a disease that returned in the 1980s and has not disappeared. According to the Ministry of Health, 994 Brazilian cities are at risk of zika, dengue and Chicungunha epidemics. Brindeiro says that in Rio, chicungunha is not alone and mayaro may be the cause of part of the cases.
Patients' suffering and treatment are the same. What changes is the difficulty of controlling epidemics, with one more virus in circulation – explains Brindeiro.
Confused with chicungunha, mayaro has been in Rio since 2016. And the seriousness of the discovery is that the cases are autochthonous. That is, people were infected here, they did not travel to endemic regions. There are three cases, all of Niteroi and only identified thanks to a molecular study. On a population scale, the three episodes mean that out of every 100 people with Chicungunha, ten have mayaro fever, Brindeiro estimates.
– The underreporting of Chicungunha itself is large and the clinical diagnosis is confused with that of dengue. Our study is a warning about the severity of mosquito-borne fevers, he adds.
Mayaro was identified at the height of the zika epidemic, when the UFRJ laboratory initiated the molecular diagnosis of arboviruses (viral infections transmitted by mosquitoes) circulating in the Southeast. By 2016, 279 samples had clinical indications (symptoms) of chicungunha. However, 57 gave inconclusive results.
Inconclusive cases are expected because the PCR test used detects only the virus during a short time window (5 days in the blood and 20 days in the urine). However, the percentage of inclusive cases reached 20%, much more than would be normal.
The research group then started searching for other viruses and mayaro was found in three patients. The cases were then investigated and found to have come from the same city, from people who had never been to endemic areas of Mayaro and who had neighbors with similar symptoms. All three were negative both by PCR (molecular) and by serology (antibodies in the blood) for zika, dengue and chicungunha, explains the virologist Orlando Ferreira, at the head of the serological tests.
The next step for scientists will be to find out where the virus came from through genomic and serology analyzes. One possibility is the Amazon or some state of the Midwest. Another is that it was brought from Haiti, where there was a recent epidemic. It could have been brought by immigrants or one of the military personnel who were part of the Brazilian forces at the service of the UN there.
They also hope to know if mayaro was disseminated by the haemagogue, which is very common in the forests and has proved to be effective in propagating yellow fever in Minas Gerais, Espírito Santo, Rio de Janeiro and São Paulo. Or, in a more serious hypothesis, began to be spread by the
, by stilt or both urban mosquitoes.
It will be possible to discover the mosquito through the reconstitution of the virus, a study that is in charge of the virologist of UFRJ Clarissa Damaso.
With no resources to expand the research, scientists hope to analyze at least 400 samples this year from Rio, Maricá and Miracema municipalities. And they note the importance of looking for the Mayaro in the mosquitoes of Rio.
"We need to know what viruses are in circulation. The climate is favorable to the proliferation of mosquitoes. It is a serious public health issue, "says Tanuri.