Winter Cuts Short Eastern Equine Encephalitis in New York

Culiset melanura (Photograph by C. Roxanne Connelly, University of Florida.)

The Onondaga county of New York reported the second human case of Eastern Equine Encephalitis in September this year.

New York County Map (Source
New York County Map (Source

EEE is caused by a virus belonging to the genus Alphavirus, of the family Togaviridae. It has been especially active this year in US, causing a number of equine cases as well as human cases (as evinced here). The virus is spread by the Culiseta melanoma mosquito, which is a swamp breeder and as such is difficult to control. The best way to prevent the disease is to avoid mosquito bites.

However, now that the winter has set in in New York and temperatures have started to plummet, the transmission of EEE virus is expected to have been cut out. Though EEE has only a few cases per year, it has the potential to spread rapidly provided it has a large enough vector population in contact with a vulnerable population. The mosquito has affinity for both human and animal blood meals, which makes it likely that the virus manages to survive in reservoirs like horses and other mammals that can harbour the virus without developing significant symptoms or falling sick or mounting a significant immune reaction that can wipe out the agent. The virus, usually circulates in birds of the Passerine order, which is a large population in itself! The Culiseta mosquito is responsible for maintaining the circulation of the virus in these birds.

EEE causes a significant disease in men who might be affected symptomatically. In addition to having no specific treatment, this disease has a 33% mortality even when patients are treated symptomatically. To make matters worse. it leaves behind significant neurological sequelae in those who do survive the episode.

Though it seems that the transmission cycle for this year has been interrupted, with global climate change, and the increased geographical range of all species and genera of mosquitoes, this disease could well be one to look out for in the days to come.

Culiset melanura (Photograph by C. Roxanne Connelly, University of Florida.)
Culiset melanura (Photograph by C. Roxanne Connelly, University of Florida.)

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