Eastern
equine encephalitis (EEE) virus poses emergent threat

EEE : A
mosquito-borne illness

New Delhi,
21^st November 2019 : Although eastern equine encephalitis (EEE), a
mosquito-borne illness, has existed for centuries, 2019 has been a particularly
deadly year for the disease in the United States. As of November 12, 36
confirmed cases of EEE had been reported by eight states; 13 of these cases
were fatal.

In a new
commentary in The New England Journal of Medicine, officials from
the National Institute of Allergy and Infectious Diseases (NIAID), part of the
National Institutes of Health of U.S. Government, describe the eastern equine
encephalitis virus (EEEV) that causes EEE, current research efforts to address
EEE, and the need for a national strategy to address the growing threat of EEEV
and other emerging and re-emerging viruses spread by mosquitoes and ticks
(known as arboviruses).

EEEV is
difficult to isolate from clinical samples

There were 12
documented U.S.-based EEE epidemics between 1831 and 1959. The virus is spread
between Culiseta melanura mosquitoes and various tree-perching
birds found in forested wetlands. Occasionally, other mosquito species transmit
the virus to people and other mammals. In people, EEEV takes roughly 3 to 10
days to cause symptoms. The virus initially causes fever, malaise, intense
headache, muscle aches, nausea and vomiting; specific diagnostic testing may
not reveal anything as EEEV is difficult to isolate from clinical samples, and
testing for EEEV antibodies may be negative.

Neurologic
signs of EEE (Eastern equine encephalitis)

Neurologic
signs of EEE, which may appear within 5 days of infection, initially are
nonspecific but rapidly progress. Most people (96%) infected with EEEV do not
develop symptoms; however, of those who do, one-third or more die, and the
others frequently suffer permanent and severe neurologic damage.

No
antiviral drug effective against EEE

Although
point-of-care diagnostics for EEE and many other mosquito-borne causes of
encephalitis are not available, currently they would be of limited value in the
absence of effective treatment, the authors write. So far, no antiviral drug
has proven safe and effective against EEE, but many compounds are being
assessed.

Monoclonal
antibodies have been
found effective in an experimental animal model but only when given prior to
infection. Patients with EEE are currently treated with supportive care, which
often includes intensive care in a hospital and ventilator assistance. Patients
with EEE are not infectious, and social support and counseling for both the
patient and the family are vitally important given the seriousness of the
disease, the authors write.

Several EEE vaccine candidates are in development but may have trouble reaching advanced development and licensure, according to the authors.

EEE outbreaks are rare, brief and focal, and occur sporadically in unpredictable locations, making it difficult to identify an appropriate target population for vaccination. Efforts to develop mosquito-saliva vaccines that would be effective against multiple mosquito diseases, including EEE, are in early stages.

In the
absence of effective EEE vaccines and treatments, state and local health
departments can provide an early warning of imminent human infections by
surveilling horses, birds and mosquitoes, but these efforts are threatened by
insufficient funding, according to the authors.

In recent
years, the Americas have seen a growing number of emerging and re-emerging
arboviruses, such as dengue, West Nile, chikungunya, Zika and Powassan.
Although outbreaks of EEE disease thus far have been infrequent and focal, the
spike in cases in 2019 and the looming presence of other, potentially deadly
arboviruses in the United States and globally demand a national defense
strategy for arboviruses and other vector-borne diseases, the
authors write. Although the best way to address these viruses is not entirely
clear, to “ignore them completely and do nothing would be irresponsible,” say
the authors.

Authors of the article “Eastern Equine Encephalitis Virus — Another Emergent Arbovirus in the United States” published in NEJM are David M. Morens, M.D., Gregory K. Folkers, M.S., M.P.H., and Anthony S. Fauci, M.D.

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