The boy, who was prone to asthma attacks and had breathing difficulties, was put on ventilator support after he turned critical on Sunday.
Swine flu has claimed its first victim in Tamil Nadu with the death of a 4-year-old boy at a private hospital in Chennai on Monday.
Hospital authorities said the boy, who had tested positive for A (H1N1) virus, died due to multiple-organ failure at 8.35 a.m.
Three other persons who were in contact with the child, including his brother have tested positive, according to Health department officials. They were already started on Tamiflu on Sunday.
The boy, who was prone to asthma attacks and had breathing difficulties, was put on ventilator support after he turned critical on Sunday, official sources said.
Initially admitted to the hospital for kidney failure, the victim was also being treated for swine flu after swab samples tested positive to the H1N1 virus, they said.
Despite treatment, his condition continued to worsen, which led to multiple organ failure, the sources said.
The Tamil Nadu government had said on Sunday that it wanted to "re-validate" swab tests done on the boy, since only gastric-related samples were sent for tests and not the usual nose and throat samples.
S. Ilango, Director of Public Health and Preventive Medicine, said it "was not a typical case" since the boy had not travelled to any country, although his father had recently gone to Singapore.
The boy was referred to the hospital from another private hospital for dialysis, Dr. Ilango said, adding that he had earlier undergone treatment for fever.