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My name is Scott Weaver.
I'm going to be discussing today vector-borne alphavirus infections.
This lecture will include the systematics and evolution of the alphaviruses,
their structure and replication,
their disease and pathogenesis as well as diagnosis,
control and prevention of these alphaviral diseases.
Then I'll be discussing in more detail a few of
the major alphavirus pathogens, including Venezuelan, Eastern,
Western and Mayaro viruses that occur in the New World,
as well as chikungunya and Ross River viruses that are found in the Old World.
A number of the alphaviruses are considered naturally emerging pathogens.
These especially include Venezuelan equine encephalitis virus,
which causes major epidemics in equids in people in various locations in the America.
These can involve up to hundreds-of-thousands of
human and equine cases with very severe morbidity in humans and occasional fatalities.
But in equines the fatalities tend to be very frequent.
Eastern equine encephalitis virus causes more sporadic human and equine disease,
principally in North America in the case of humans,
but also throughout Latin America for equids.
Case fatality rates are extremely high for this virus,
better than 50 percent both for humans and equids.
Many survivors, humans, suffer from severe neurologic sequelae.
Western equine encephalitis virus also causes sporadic human and equine disease.
Again, equine disease can occur throughout the New World,
but human disease tends to occur only in North America.
The incidence of both equine and human disease has
reduced dramatically since the first half of the 20th century.
We really don't understand why.
Chikungunya virus is a very important Old World alphaviruses that
cause epidemics of a different disease syndrome characterized by arthritis and rash.
This occurs in Africa and Asia.
Recently this virus was imported into islands of the East Coast of Africa,
as well as into India,
Italy in Southeast Asia.
Ross River, Mayaro and o'nyong-nyong viruses are
other Old World viruses that cause the same disease syndrome of arthritis and rash.
They tend to cause sporadic outbreaks in many locations in the tropics and subtropics.
Finally, all of these alphaviruses that are human pathogens are greatly under
appreciated as human pathogens primarily
because without sophisticated laboratory diagnostics,
it's nearly impossible to diagnose these diseases clinically and to
distinguish them from the very common diseases of the tropics like dengue and malaria.