Thrissur (Kerala), Aug 9 - A nine-year-old boy, who arrived from the US with his parents a week ago, has tested positive for influenza A (H1N1) virus, a health official said Sunday.

With this, the total number of infected people in the state has touched 52.

The official said the sample of the boy was sent on Aug 7, four days after he arrived from the US. The report sent Sunday said the boy is positive for swine flu.

The boy has been moved to an isolation ward at the Thrissur district hospital, the official said.