Discussion 
Birds are essential to cycles of some arboviruses and other zoonotic 
agents. The birds may enter in virus cycles in two ways, 1) maintenance 
of viruses in endemic or epidemic local foci and 2) the transport of viruses 
over long distances through bird migration. The results of this study apply 
mainly to the latter. 
Viruses were isolated from the blood of migrating birds on 54 occasions 
in Egypt and Cyprus indicating clearly the potential for transport of viruses 
by migratory birds. In no case is it clear that virus from a migrating bird 
became established in a host-vector cycle in a new geographical area. There 
is evidence for involvement ofpalearctic birds with at least seven viruses 
for which something is known of their world-wide distribution and epidemiology 
in endemic foci: West Nile, Sindbis, Ingwavuma, Kemerovo, Uukuniemi, Thimiri 
and the Tete group of viruses. 
West Nile virus epidemiology has been extensively studied in Egypt 
(Taylor ^ 1956) where man is usually involved in early childhood with a 
mild febrile infection transmitted by mosquito bite. The virus cycle involves 
birds and the mosquito, Culex univittatus . Isolations from birds have been re¬ 
ported in South Africa, Egypt, Israel, Russia, Borneo, and Cyprus (Taylor, 1967). 
There are at least 3 different geographical subtypes. In the present study in 
Cyprus, West Nile of the sub-Saharan subtype was recovered from a northward 
migrating Barred Warbler, Sylvia nlsoria , strongly suggesting that the warbler 
had been infected in its wintering grounds and had transported the virus over a 
long distance into Europe. This does not mean necessarily that introduction of 
West Nile led to its establishment in a new focus in Europe. 
Human infections v/ith Sindbis virus have been recorded in Uganda and South 
Africa, (Taylor, 1967); however, the virus itself has been recovered from many 
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