As the numbers of suspected bird flu cases in Turkey rises there is concern that the deadly virus is rapidly spreading across the country and is heading for mainland Europe.
To date a total of 23 people are currently undergoing tests for bird flu in Istanbul, and among that number are 14 children.
Istanbul is a heavily populated city of 12 million and is the country's centre of commerce; it is also the gateway to Europe from many Asian countries.
Istanbul is about 400 km west of Ankara.
Turkey has experienced the first incident, outside east Asia, of the H5N1 virus jumping from birds to humans.
In that outbreak three children from the same family died, in poor part of rural Turkey, in the east of the country.
Doctors are convinced the children who died last week caught the virus directly from diseased chickens; health officials say the children had been playing with the severed heads of infected birds.
There is on-going concern on the part of world health authorities that human exposure to the bird flu virus could lead to the emergence of a mutation allowing easier transmission between humans which might develop into a global pandemic.
Health officials in Turkey have confirmed that there are human outbreaks of the virus in three broad areas, the east where the disease first emerged last week, the central region around the capital Ankara, and Black Sea areas in the north.
Turkish authorities say that three people from villages in the Ankara region had tested positive for the virus, the farthest west that any case of bird flu in humans has been reported, and appears to be the latest stage in a spread towards major economic centers in Turkey and Europe.
According to Turkey's Health Minister Recep Akdag, to date the total number of cases in the country is 14 which have been confirmed by laboratory tests, and of those 14, three children have died.
The minister was speaking in the village of the three children, Dogubayazit, and he appealed to the people there to stay away from poultry, and to also keep their children away from the birds.
He says he believes the number of people being checked is large because people feeling generally ill are checking themselves into hospital as a precaution.
At present the World Health Organization (WHO) has only confirmed four cases in Turkey, including two deaths.