HOUSTON -- He was not yet 2, far from home and dying. The first victim of swine flu in the US was a Mexican toddler who struggled to survive for weeks in Texas hospitals, long before it was known doctors were dealing with an international outbreak.

Now the hunt is on to find anyone who came into contact with the little boy while he visited relatives in the border city of Brownsville from his home in Mexico City.

The state's health director, Dr. David Lakey, at an Austin news conference, called it "highly likely" that the boy contracted the disease in Mexico before his trip to the US.

The boy, who was 23 months old, had "underlying health issues" before he flew to Matamoros, Mexico, on April 4 and crossed into Brownsville to visit relatives, state health officials said.

He developed flu symptoms four days later and was taken to a Brownsville hospital April 13 and transferred the following day to Texas Children's Hospital in Houston, where he died Monday night.

The US Centers for Disease Control and Prevention on Wednesday confirmed that he had been infected with the swine flu virus. The cause of the death was pneumonia caused by the virus, Cascos said.

Health officials insisted the boy posed no contagion threat to Houston. He had no contact with other patients at Texas Children's Hospital and none of the staff was exposed, said Dr. Jeffrey Starke, the hospital's director of infectious disease.

This case "shouldn't trigger any undue alarm in the community," Starke told a news conference. "The child did not acquire the virus in Houston, Texas."

Dr. Brian Smith, regional director of the Texas Department of State Health Services, said antiviral treatments were given to family members who had close contact with the child and none had contracted swine flu. He said that with the virus' short incubation period, health officials would have begun seeing secondary cases among the child's close contacts by now, but none has appeared.

Although the boy wasn't initially identified as a swine flu case, Starke said concern grew over the last several days as news of the virus intensified.

Officials refused to release any further information about the boy or his family, including his name or any details on his other health issues, citing privacy laws.

Starke said the child was "critically ill the entire time the child was under our care," and that he was transferred to Houston because the hospital in Brownsville, an impoverished border city of 140,000, couldn't provide the kind of care he needed.

Swine flu is suspected of killing more than 150 people and sickening over 2,600 in Mexico, Canada, New Zealand, Britain, Germany, Spain, Israel and Austria.

The virus has spread to 11 US states from coast to coast. Total American cases surged to nearly 100, including a Marine at the Twentynine Palms base in southern California. Authorities have confirmed at least 93 swine flu cases in the United States.