Nile fever in Piauí: 285 investigated cases since 2013

The 10 suspicious cases returned positive serological results for WNF, but with cross-results for other flaviviruses, what invalidates the confirmed results before PRNT tests

The Piauí State Health Secretary notified 10 suspicious cases for Severe Neuroinvasive Disease by the West Nile Fever virus. The cases refer to laboratory exams results from 2017, at the Evandro Chagas Institute (IEC), Health Ministrys reference laboratory. All exams presented cross-reaction (simultaneous positivity) with at least one other flavivirus, among them, zika, dengue and Saint Louis Encephalitis. Of these notifications, there was one death among the probable cases, a patient from Teresina – PI.

According to neurologist Doctor Marcelo Adriano, from the Natan Portella Tropical Diseases Institute and member of the Epidemiology Management Office at the Teresina city Health Foundation (FMS/PI), at first, it would be early to establish any conclusion about the cases, since they are still waiting for results from the reference laboratory and field investigations performed by the epidemiology team.

Probably human cases already occurred and occur in other states, but with no diagnosis. Serological evidence of the virus activity have been found in animals in other Brazilian states. However, Piauí implemented a pioneer sentinel surveillance system for encephalitis and other neurological syndromes in the Country, reason why it detects the cases.

Doctor Vieira stresses that since 2013 there is a regular and stable rhythm, or better expressed, cyclic, of notifications in Piauí, because the surveillance happens in a sentinel way. All encephalitis and some other neurological syndromes cases in the state are investigated; therefore, they are listed as suspicious for West Nile Fever, besides other arboviruses, as etiology. The annual occurrence of these cases remains stable, tending to peek during rainier periods, explains the physician. According to numbers from the Piauí State Health Secretary, there are 285 cases under investigation, since then.

In an official notice, the Piauí State Health Secretary informed that all cases have been followed and has taken all actions due to the Health Surveillance and Attention board, among them: in cooperation with the Teresina city Health Secretary, performing field investigation, which involves identifying and studying vectors, building an action plan to face the disease; and implement the Natan Portella Tropical Diseases Institute as a reference unit in the state do diagnose and treat West Nile Fever. Besides this, the board has notified the Health Ministry of these results which, to be confirmed, need to be ratified by more complex and longer lasting tests.

West Nile Fever or Occidental Nile Fever causes neurological damages and could be fatal

Infectologist and Tropical Medicine expert, Doctor Dalcy Albuquerque Filho said the West Nile virus was first isolated in Uganda, in 1937. In the Americas, it first appeared in 1999 in the USA, from where the virus spread to the rest of North, Central and South Americas. In Brazil, it has been reported circulating among birds and horses, however, only one human case has been confirmed until now. The transmission happens through the bite of infected mosquitos, possibly, in birds carrying the virus. The main genus involved in the transmission is the Culex. The Culex quiquefasciatus and Aedes albopictus, both with records of virus isolation are abundant mosquitoes in Brazil, what makes them potential vectors.

Usually the infection causes unapparent clinical manifestations. It is estimated that only 20% of the infected individuals develop light symptoms, with abrupt onset acute fever, malaise, anorexia, nausea/vomits, eye pain, headache, myalgia (body pain), papular exanthema (body redness) and lymphadenopathy (palpable nodes), very similar to other arboviral diseases, as dengue or chikungunya.

The severe neurological disease (meningitis, encephalitis or poliomyelitis), has older ages (> 50 years) as a greater risk factor. Encephalitis is the most frequent neurological manifestation. Besides the mentioned signs/symptoms, it also causes changes in the mental pattern, severe muscular weakness, flaccid paralysis, and ataxia and extrapyramidal signs (twitching), head nerve abnormalities, myelitis, optical neuritis, polyradiculitis and convulsion.

The diagnosis is performed by serology, to detect IgM antibodies (ELISA) against the West Nile virus, collected between the 8th and 14th day after symptoms appearance or cerebrospinal fluid collected until the 8th day after symptoms appearance. Also by polymerase chain reaction (PCR), viral isolation and immunohistochemistry histopathological exam (necropsy).

There is no specific treatment. For moderate/mild cases, treatment is symptomatic with careful assistance to the patient that must remain in observation. For the severe forms, treatment is supportive, hospitalized, with fluid reposition, respiratory assistance and prevention of secondary infections. May require Intensive Care Unit (ICU).

It is a disease of obligatory immediate notification. Any suspicious case must be reported immediately to the sanitary authorities (SMS or SES), since this is a disease with potential dispersion risk on national territory, stresses Dr. Albuquerque.…