source of the infection?

LATimes | Swine flu is suspected in at least 149 deaths and 1,995 cases, with nearly all states reporting infections. Officials look at what is thought to be the first case, near a pig farm in Veracruz.

Reporting from Mexico City — With the death toll climbing, Mexican authorities at the center of an international swine flu epidemic struggled Monday to piece together its lethal march, with attention focusing on a 4-year-old boy and a pig farm.

The boy, who survived the illness, has emerged as Mexico's earliest known case of the never-before-seen virus, Health Secretary Jose Angel Cordova said Monday. It provides an important clue to the unique strain's path.

The boy lived near a pig farm run by a U.S.-Mexican company, Granjas Carroll, in the municipality of Perote, in Veracruz state on the Gulf of Mexico. He contracted the disease on April 2, Cordova said, one of a group of residents who came down with what was at the time labeled a particularly bad case of the flu.

Only one sample from the group, that belonging to the boy, was preserved. It was retested after other cases of the new strain were confirmed elsewhere in the country, Cordova said. The boy had the same disease. It is unknown how many more of the hundreds of people who fell sick in Perote also were infected by the strain.

In an ominous disclosure, officials said the first confirmed fatality of the disease, a 39-year-old woman from an impoverished state neighboring Veracruz, worked as a door-to-door census-taker and may have had contact with scores of people.

In Perote, residents of the hamlet known as La Gloria have complained since mid-March that contamination from the pig farm was tainting their water and causing respiratory infections. In one demonstration in early April, they carried signs with pictures of pigs crossed out with an X and the word "peligro" -- danger. Residents told reporters at the time that more than half the town's 3,000 inhabitants were sick and that three children under the age of 2 had died.

Local health officials mobilized when the outbreak was first reported, but they gave a different account: The infection may have started with a migrant farmer who returned from work in the U.S. and gave the disease to his wife, who in turn passed it on to other women in the community.

(Smithfield) Granjas Carroll, which claims to be Mexico's leading pig farm at a million head a year, issued a statement Monday saying none of its employees had shown any signs of illness and noting that the sick are people who had no contact with its pigs. It is but one of numerous farms in the region.

The United Nations' Food and Agriculture Organization announced Monday that it was sending a team of experts to inspect pig farms in Mexico. The agency's chief veterinary officer, Joseph Domenech, said the teams would attempt to determine whether the new strain was circulating among pigs and then trace linkage to human populations.

The first officially confirmed fatality from the disease occurred April 13. Maria Adela Gutierrez died in the southern city of Oaxaca, capital of the state of the same name.

Gutierrez was a door-to-door census-taker for the tax board, meaning she could have had contact with scores of people at her most contagious point, before being hospitalized. But Martin Vazquez Villanueva, the regional health secretary in Oaxaca, denied local news reports that said she had infected 20 people, as well as her husband and children.