Research evaluates simultaneous transmission of arboviroses

Since 2014, great chikungunya and zika fever epidemics have ravaged Brazil and other countries in the Americas, being added to dengue fever to compose a group of mosquito-transmitted febrile diseases that represent an emerging urban public health issue: the arboviroses. Thus, the correct clinical differentiation of each one of those diseases has become even more difficult. Furthermore, a simultaneous infection (coinfection) by more than one virus becomes possible, and the implications of such occurrence related to the clinical presentation and evolution are little evident.

Considering the challenges and gaps in the knowledge referring to the rate coinfections occur during intense cotransmission periods for different arboviruses, to which clinical manifestations are more frequent in each of such infections, and to the doctors' capacity to correctly suspect their diagnosis, the Fiocruz Bahia researcher and teacher in the Medicine College of the Federal University of Bahia (UFBA) Guilherme Ribeiro has led a study aiming to answer these questions. Conducted from September, 2014 to July, 2016, the research included 948 patients attended by febrile diseases in an emergency health unit in Salvador, which were systemically investigated by laboratorial tests to verify if the disease cause could be attributed to the dengue fever, chikungunya, or zika fever viruses.

The work results were published in the scientific periodical Clinical Infectious Diseases, one of the most recognized means to disclose research results in the field of infectious diseases. Besides the researchers from Fiocruz Bahia and UFBA, postdoctoral, doctoral, graduate, and scientific initiation students and researchers from the international institutions Yale University, Emory University, and University of Texas Medical Branch, all located in the USA, also participated in the research.

The results have indicated that these three arboviroses are a significant cause of febrile diseases that affect those that attend to an emergency unit. Twenty-six patients of of the 100 patients included in the study presented an acute infection by one arbovirus type, with 24 presenting an infection caused by only one of the arbovirus type, while 2 presented a coinfection by two arboviruses. The high detection rate for infections and coinfections by arboviruses among the investigated febrile patients occurred due to an intensive simultaneous transmission of the three arboviruses in Salvador during the study period.

It was also observed that the clinical manifestations of dengue fever, zika fever, and chikungunya were usually similar. However, the patients with zika fever presented skin rash and pruritus more frequently than those who presented dengue fever and chikungunya. On the other hand, joint pains were more common in those who presented the chikungunya diagnosis, compared to those who were diagnosed with dengue and zika fevers. Despite these differences, the doctors presented high difficulty in correctly clinically suspect a diagnosis, considering that the highest correct answer occurred for patients that received a laboratorial diagnosis of zika fever, with such correct answer only corresponding to 23%. A portion of such difficulty in correctly clinically suspect a diagnosis was due to the fact that the transmission of the chikungunya virus in Salvador was still not fully evident in the period.

The study (conducted during a period of intensive simultaneous transmission of dengue fever, chikungunya, and zika fever) concluded that the arboviroses are a significant cause of febrile diseases and indicated that coinfections are common in such circumstances. Given the clinical similarities among these three arboviroses, there is an urgent need for developing diagnostic tests that simultaneously detect these three infections, providing a result in short time, and that can be conducted in first aid units, without need for a specialized laboratory. Furthermore, epidemiological information about seasonality, population susceptibility, and transmission intensity for such viruses in each location are needed to guide the doctors in their clinical suspicion.