(1), Sylvia hortensls (1), Monticola saxatllis (1), Phoenicurus 
^hoenlcurus (1), and Lusclnia megarhynchos (1), All of these plasmas also 
neutralized Sindbis virus except Sylvia curruca (negative) and Sylvia hortensis 
* 
(not tested). Ten control plasmas, of corresponding species where possible, 
were both HI and neutralization negative. 
West Nile . Group B HI antibody (Table 10) was found in Streptopelia 
turtur (8), Otus scops (1), Upupa epops (2), Falco tinnunculus (7), Emberiza 
calandra (1), Emberiza melanocephala (1), Qriolus oriolus (2), Lanius nubicus (2), 
Lanius collurio (1), Lanius minor (1), Phylloscopus collybita (1), Phylloscopus 
trochilus (1), Phylloscopus bonelli (1), Acrocephalus arundinaceus (2), Sylvia 
communis (2), Sylvia ru.ppelli (1), Sylvia curruca (3), Sylvia atricapilla (1), 
Sylvia nisoria (6), Sylvia hortensis (2), Monticola saxatilis (2), Turdus 
philomelos (1), Oenanthe oenanthe (1),. Penanthe pleschanka (1), Penanthe 
isabellina (2), Erithacus rubecula (1), and Anthus trivialis (1). 
The majority of the HI positive reactions were higher in titer with West 
Nile antigen than with other group B viruses. Since West Nile virus was isolated 
from Sylvia nisoria , it appears most likely that West Nile infection was responsi¬ 
ble for the observed group B HI antibody. Neutralization tests with West Nile 
also indicated correlation between HI positivity and increased survival time of 
mice; complete neutralization of approximately 100 LD^q occurred in 17 of 48 of 
the above plasmas; prolonged survival time occurred in another 22. An equal 
number of control HI negative plasmas were tested, only 6 of which had neutrali¬ 
zation or prolonged survival time. Four of these 6 were from the Roller family. 
The possibility of one or more group B viruses other than West Nile being 
responsible for some of the observed group B HI reactions must be considered. 
Ingwavuma . Ingwavuma HI antibody (Table 11) was limited to the following 
passerines : Emberiza caesia (1), Oriolus oriolus (2), Sylvia melanothorax (1), 
72 
