Japan tested a 4-month-old US baby who tested positive for A strain flu preliminary but said it is unlikely to have been infected with the influenza A/H1N1, Japanese government sources said on Sunday.

The baby arrived at the Yokota Air Base in Tokyo from the United States on a US military-chartered plane on Friday and tested positive for the type A influenza virus in a preliminary examination.

The baby and the mother were isolated after the first tests proved positive, the Foreign Ministry has said.

Test samples from the infant were taken to the National Institute of Infectious Diseases in Tokyo from the base on Saturday for detailed tests.

Kyodo News said in an early Sunday report that the results of the genetic screening showed that it is unlikely the baby has the influenza A/H1N1, citing unspecified government sources.

Japan earlier clarified the country's first suspected case, a Yokohama high-school student, was a false alarm. It has no confirmed case of the new strain of the influenza A/H1N1 up till now.

(Xinhua News Agency May 3, 2009)