First isolated in
the West Nile District of Uganda in 1937, the West Nile Virus (WNV) was
imported to the USA in 1999, generating
an outbreak that would last 11 years later. A member of the Flaviviridae
family, WNV infects humans mostly through mosquito vectors which are in turn
infected by feeding on birds that have the virus circulating in their blood.
After first
appearing in New York in 1999, the virus appeared in Maricopa county, which
houses the Phoenix metropolitan area four years later in 2003. Scientists
suggest that the increase in milder winters in the county allow snowbirds and
other avian species that carry the virus along with infected mosquitoes to
survive and act as virus reservoirs. Thus as the weather warms up, they
generate waves of infections as the winter season ends. In 2017, there were 110
cases of WNV infections in Arizona, and the virus existed in 221 mosquito pools
in Phoenix.
The strain of WNV in
the county appears to be endemic to the area, rather than repeatedly imported,
having been circulating in Maricopa for the last seven years. In 2017, the same
strain has also been reported in southern California and southwestern Utah.
Most people with the
virus do not realize that they are infected, with signs and symptoms mirroring
the flu, such as nausea, vomiting, fever and headaches. A small fraction of
people infected can develop serious conditions including paralysis, meningitis
and encephalitis, and those aged 50 years and older are at a higher risk of
infection.
-Riasoya Jodah
Read more at: From
<https://www.miamiherald.com/news/article224833895.html>
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