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Have Doctors Found Swine "Patient Zero?"

"Patient zero" - the first person to contract swine flu - may be a four-year-old boy in a small, rural town in the Mexican state of Veracruz.

Edgar Hernandez, officials say, tested positive for swine flu in early April, CBS News correspondent John Blackstone reported on The Early Show Wednesday. But, it's unclear if Hernandez is indeed the first case of the new flu spreading around the world.

For months, Blackstone said, residents of the mountain community had been complaining about pollution from a local pig farm, but it's not known if his virus originated from pigs.

"It's impossible to know whether this boy got infected from a pig, and whether this boy was the index case for this particular outbreak," said Dr. Jeffrey Kahn, a Yale University pediatric infectious disease specialist.

Hernandez has recovered, but the community is still on high alert.

Blackstone added that officials are investigating how swine flu could have spread from rural Veracruz, throughout Mexico, and around the world -- if Veracruz is really its starting point.

One factor may be increased travel across the Catholic country during the Easter holiday.

Another culprit may be widespread poverty. While officials urge frequent hand-washing, shortages have left some Mexico City neighborhoods with no running water.

Blackstone wondered whether that could be the reason that at least 159 people have died from swine flu in Mexico, but the virus seems much milder in the United States.

"Until we know how many people were infected in Mexico," Kahn said, "we will not be able to determine the case fatality rate due to this virus."

Over 1,300 people are currently being treated in Mexican hospitals for the virus.