Health officials have banned residents of sixteen districts in greater Athens from donating blood in a bid to avert the spread of the virus, which can cause encephalitis.
Similar measures have been imposed in Evia, Samos, Naoussa and Thessaloniki.
The West Nile virus was discovered in 1937 in Uganda. Sporadic cases of the disease in humans have occurred in Europe since the 1960s. It was first detected in Greece in 2010, when 262 people contracted the disease, 35 of whom died.