Arboviral diseases are an important and constant threat in tropical regions

Oropouche, Mayaro, West Nile Fever, Saint Louis encephalitis, zika, dengue and chikungunya are only some of the 210 arboviral diseases currently circulating in Brazil that represent a potential threat to the populations health

The number of registered arboviruses in Brazil has doubled in the past three decades. According to registers at Evandro Chagas Institute, reference center in Tropical Medicine, 210 arboviruses already circulate in the Country. This number was 95 in the 1980s. At least 37 are able to cause diseases in humans. Arboviral diseases have been a major challenge for public health and the current worrying situation in the Country reflects a complex context, in which, on one hand the general ineffectiveness of public organs and the general society interact with each other, and on the other factors related to climate and environment changes and deforestation favor the amplification, viral transmission besides overcoming the barrier between species.

According to data from the Health Ministry, in 30 years, approximately 12 million people will have been infected by diseases transmitted by the Aedes aegypti, which transmits other 17 arboviral diseases besides dengue. All arboviral diseases are a public health issue and deserve increased attention. This demands more awareness with effective and permanent measures. To have a broader view of the matter, the Brazilian Society of Tropical Medicines (BSTM) press board talked to the neurologist at the Natan Portella Tropical Diseases Institute and member of the Epidemiology Board at the Teresina Municipal Health Foundation (FMS/PI), Dr. Marcelo Adriano Vieira.

BSTM: Why the past years have revealed the increase of cases compromising the central nervous system (CNS) in patients infected by arboviral diseases?

Dr. Marcelo Adriano: Arboviral disease always had a close link to the central nervous system, as was observed in patients with Japanese encephalitis, equine encephalitis, Venezuela encephalitis, West Nile and Saint Louis encephalitis. However, the recent burst in cases of dengue, zika and chikungunya has reached dimensions often observed in the past, putting neuroinvasive cases in the spotlight. Besides this, Zika virus has brought the news of compromising the nervous system still in prenatal phase, by detecting congenital microcephaly cases.

BSTM: What is the potential threat arboviruses place to human health in Brazil, especially regarding the CNS?

Dr. Marcelo Adriano: Most of the deaths related to human infections by arboviral diseases still owes to hemorrhagic complications. Absenteeism related to lethal cases generates a significant economic impact. Chronic inabilities due to persistent joint complications related to chikungunya virus extensively affects the individuals well-being and the public health systems assistance in the most affected regions. Microcephaly outbreaks related to mother-child infection by Zika virus has short, medium and very long-term consequences, with a potential to leave an impression in an entire generation. By finding favorable ecological niches, many arboviruses can cause outbreaks of encephalitis, myelitis and encephalomyelitis.

BSTM: Do you believe neurotropic viruses as chikungunya and zika are able to cause neurological syndromes – also leading to psychiatric manifestations? Can these be related to developing post-infection acute psychiatric disorders?

Dr. Marcelo Adriano: Yes. Inclusive, there are some reports in the scientific literature about the subject. Besides this, we must keep in mind that up to 50% of the survivors of viral encephalitis develop cognitive, psychiatric or motion disorders, regardless of the specific etiology.

BSTM: There is little information in literature relating Zika virus to neurological manifestations. There is a report in a French Polynesian article about a patient who developed Guillain-Barré Syndrome after 7 days of an influenza-like disease. In your opinion, is Zika a virus with a smaller chance to strike the nervous system?

Dr. Marcelo Adriano: The available evidences are insufficient to compare the odds of Zika compromising the nervous system compared to other arboviruses. However, there are described cases of confirmed cases of encephalitis, myelitis, encephalomyelitis and polyradiculoneuritis associated to post-natal infection by Zika virus.

BSTM: The association of dengue infection to neurological manifestations was reported in 1976. What changed since then?

Dr. Marcelo Adriano: Currently, diagnostic tests for dengue virus are part of etiological laboratory investigation routine for encephalitis and aseptic meningitis cases in several health centers around the Country, even those with no classic symptoms of the disease.

BSTM: Approaching chikungunya, we know since the 1960s that it can affect the central nervous system, and during the early 1970s, it was associated to meningoencephalitis and myelitis. How is this situation today?

Dr. Marcelo Adriano: There are reports of atypical cases of human infection by chikungunya showing that several topographies of the nervous system can be affected, directly or indirectly (meninges, encephalon, optical nerves, spinal cord, etc.). Systematic reviews about the role of chikungunya virus in the genesis of all neuroinvasive diseases are scarce, especially in tropical countries.

BSTM: The arboviral diseases have become a major challenge to public health. What actions could take place to ease this situation?

Dr. Marcelo Adriano: Health education, classic actions for vector control, basic sanitation and research / use of new technologies to prevent human infections and, maybe, neurological damage even for past infections. The possibility of sexual transmission of Zika virus brought a new challenge for prevention campaigns.…