Chikungunya virus arrived in Brazil at least a year earlier than believed

According to scientific research, the chikungunya virus arrived in Brazil at least a year earlier than it was detected by public health surveillance systems. The findings are from researchers at the Mailman School of Public Health, Columbia University, and the Oswaldo Cruz Foundation (Fiocruz), in an article published by the academic journal Scientific Reports, from Nature Group. The intent of the research is to assist in decision making regarding public health based on evidence, since the result leads to believe that patients were misdiagnosed in the country, mainly in Rio de Janeiro, thoughout all this period of non-identification of the new virus.

"If we have evidence that a virus has circulated for about a year without being detected - and this has happened to chikungunya and zika recently - it means that surveillance needs to be much more concerned with negative cases for preexisting viruses and start to track other possible agents with an emersion potential. Hence, it is possible to recognize this virus before it becomes a public health issue, thus avoiding a possible epidemic," explains one of the coordinators of the study, the researcher of the Center for Technological Development in Health (CDTS/Fiocruz) Thiago Moreno.

Blood samples collected at the National Institute of Infectology Evandro Chagas (INI/Fiocruz), in Rio de Janeiro, from March 2016 to June 2017, were analyzed using genetic testing to track its entry into Brazil, both temporal and geographical. From the analyzed samples, more than 60% tested positive for the chikungunya virus. In these cases, 40 chikungunya-positive samples that had negative results for dengue and zika were evaluated again using the CII-ArboViroPlex method, developed by the University of Columbia's Infection and Immunization Center (CII), which simultaneously show results for the presence of zika, all serotypes of the dengue virus, Nile fever and chikungunya. The test confirmed the previous assessment, but with greater sensitivity, suggesting the possibility of being able to identify the virus that other tests could not.

From these samples, 14 represented specific dates from the former 15-month period and were subsequently analyzed using another method of detection, surveillance and discovery of arboviruses developed by the CII. The test enabled a nearly complete recovery of DNA sequencing and identification of chikungunya virus genotypes. "Every time a virus replicates, that is, it circulates, mutations appear in the genome. And, through the ancestry of these variations we managed to map the route that the virus took here and when”, explains Moreno.

The analysis of these 14 sequences showed a strong correlation between the genetic divergence and the date the sample was collected, that is, a gap of about one year was found. This result allowed researchers to identify a "molecular clock" based on the rate of mutations between the samples. This 'clock' suggests that the virus may have circulated in early 2012, and probably came from Central Africa, after a neglected circulation for 20 years in other parts of the world. The chikungunya virus was reported by public health surveillance agencies in 2014.

"Other investigations attempted to identify evidence of the virus in Brazil in 2014, our study points to an earlier appearance of chikungunya," Thiago said. "We also note that Brazilian megalopolises, such as Rio de Janeiro, endemic for dengue, have had indigenous chikungunya virus circulation since March 2016, when it co-circulated with the dengue and zika virus. After that, chikungunya eventually became the most prevalent arbovirose in the country”, Moreno concluded.

Another important evidence from the studies indicate the entry of the virus in Rio de Janeiro within a single event, coming directly from Sergipe. That is to say, the blockade for the arborivores in the state is not being effective. “It took one single event for the virus to come and stay, and that means there are no obstacles to its circulation. It is usually expected that multiple entries are required for a new disease to be established. Thus, what we have as a result of this research is the diagnosis of the current situation. Which points us a way to be followed so we can control the entry of possible new viruses in the country”, concludes the researcher.