A team from the WHO arrived in Iraq at the weekend following the death of a teenage girl from the Kurdistan region, raising fears that the virus had spread from neighbuoring Turkey.
The girl's uncle also died and a WHO laboratory in London is testing samples to see if bird flu killed him.
Tests are also being carried out on samples from a 54-year-old woman with respiratory problems who is being treated in northern Iraq.
There are five other people whose condition gives grounds for suspecting that they could have the disease, WHO spokesman Dick Thompson said.
In January an outbreak of bird flu killed four children in Turkey, but the condition there has since been brought under control.
There are fears that anti-government violence in Iraq and a ruined infrastructure will make a bird flu outbreak much harder to control there.
A large consignment of masks, gloves and gowns is on its way from the US to help Iraqi authorities contain any outbreak.
Shanjin Abdel Qader was Iraq's
first human victim of bird flu
"What Iraq needs is lots of personal protection equipment such as masks, gloves, gowns and disinfectants to curb the spread of the disease," said Jon C. Bowersox, health attache with the US embassy.
"A 900 kilo consignment of this equipment is on its way from the United States to Iraq and will arrive here in the next two days," he told AFP.
Bowersox said the consignment will be distributed across the
"The idea is to prepare Iraq to ward off any widespread threat," he said.
No signs of spread
Naeema al-Gasseer, the WHO country representative, told a media briefing in Arbil, the capital of Iraq's largely autonomous Kurdistan region, that local health officials were confident the virus had not spread from the dead teenage girl's home village.
The girl came from Serkikan village in Raniya district, which is close to the Turkish border.
Bird flu has killed more than 80 people around the world since it reemerged in late 2003.
To date all human cases have come about through direct contact with infected or sick poultry.
However, in northern Iraq, there were no confirmed reports of sick birds before the human cases, prompting concerns that the virus was spreading undetected.
Experts fear that the virus could mutate into a form that passes easily from person to person, sparking a pandemic in which millions could die.