The health ministry in Azerbaijan, where five people have died from bird flu, has taken blood samples from 43 other people believed to be infected.
The samples have been sent to a London laboratory for analysis.
The former Soviet republic is among a number of countries whose citizens have died from the disease. Others on the World Health Organisation (WHO) list are, Vietnam (42), Indonesia (23), Thailand (14), China (11), Cambodia (six), Turkey (four), Egypt (two) and Iraq (two).
Human deaths from bird flu stood at 109 out of 192 diagnosed cases as of last Thursday. Two further human cases have been confirmed in Azerbaijan.
WHO director-general Lee Jong-Wook is to visit Azerbaijan on April 24th to discuss the bird flu outbreak among other issues, according to deputy health minister Abbas Velibeko, his first visit to the Caucasus region.
Four of the five fatalities from bird flu in Azerbaijan have occurred in the village of Daikyand in the southeastern Salyan region. Aged from 16 to 20 years, they died between February 23rd and March 10th. Three of them were close relatives and the fourth was a family friend.
The WHO says the cases may have resulted from contact with swans killed by hunters.
The village was so alarmed that many residents refused to attend the funerals, despite repeated assurances from government officials, for fear they would catch the disease. Villagers also stopped eating eggs or chicken, unconvinced by official declarations that there was no danger if they were properly cooked.