First Human Case of EEE in Arkansas Causes Teen's Death

In a recent letter published in the Emerging Infectious Diseases journal of the Centers for Disease Control and Prevention (CDC), investigators discussed the first human case of Eastern equine encephalitis (EEE) in Arkansas, which occurred in a teenage boy who died of the illness.

“Although human EEEV [EEE virus] disease cases had been reported in neighboring Louisiana, Mississippi, and Texas, no cases had previously been reported in Arkansas,” wrote Jeremy Garlick, MD, from the University of Arkansas for Medical Sciences, Little Rock, and colleagues. “However, EEEV was identified in horses in Arkansas before 2013 and in the patient’s county of residence in 2013, indicating that the virus was already present in the area.”

According to the CDC, an average of 8 cases of EEE are reported in people in the United States each year. EEE virus is an arbovirus which is transmitted to people and horses through the bite of infected mosquitoes.

EEE occurs infrequently in people, predominantly because human populations are more limited around swampy areas, which are important ecological environments for transmission of the virus from birds to mosquitoes. Most cases of EEE are reported along the eastern and Gulf coasts of North America (in Massachusetts, New Jersey, and Florida, in particular).

In people, symptoms of EEE range from mild flu-like illness to inflammation of the brain, coma, and death. Despite its sporadic occurrence, EEE leads to death in more than one-third of infected individuals, and permanent neurologic damage in more than one-half of all surviving patients.

Dr. Garlick and colleagues discussed the details of a locally-acquired case of human EEE in a teenaged boy in southwestern Arkansas. The teenager became ill in October 2013 and received hospital treatment after 3 days of headache and three new-onset focal seizures. He had recently received multiple mosquito bites, but had no recent history of travel. Until now, no significant abnormalities were found on examination of his cerebrospinal fluid (CSF), and noncontrast computed tomography (CT) of his head was normal.

Four days after the onset of symptoms, the patient had become more lethargic, febrile, tachycardic, and hypotensive. Doctors treated him with intravenous fluids and broad-spectrum antimicrobial drugs; they also performed magnetic resonance imaging of the brain which showed left frontal lobe edema and abnormalities in the basal ganglia and midbrain.

The patient’s CSF also contained markedly elevated levels of white blood cells, red blood cells, protein, and glucose. However, CSF contained no evidence of infection with bacteria, herpes simplex virus, or enterovirus.

By day 6, a CT scan of the brain showed an increased level of edema. However, despite physicians’ aggressive attempts to control the patient’s intracranial pressure, it continued to increase, reaching 71 mm Hg on day 19. At this time, a CT scan of the brain showed widespread cerebral edema, hemorrhages, uncal herniation, and obstructive hydrocephalus. Due to his worsening clinical condition, the family chose to withdraw care, and the patient died.

Serologic tests performed on serum collected on day 4 were positive for EEE virus, and negative for St. Louis encephalitis virus, West Nile virus, and California serogroup viruses. The CDC later tested serum collected from the patient on day 12 and confirmed the presence of EEE virus infection.

Although this boy is the first person to develop EEE in Arkansas, the disease had been reported in his area of residence in 2013, indicating that EEEV was present in the area at the time of the teenager’s illness. According to the authors, the patient also lived within 6 miles of freshwater swamps.

“This case shows that human EEEV disease can occur in areas where EEEV is circulating in the environment, highlighting the need for continued surveillance for EEEV and other arboviruses,” they concluded.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.

Feature Picture Source: Fred Murphy; Sylvia Whitfield / Centers for Disease Control and Prevention