Doctors tracking swine flu in California are investigating a new theory: What if it didn't originate in Mexico but instead had been floating around the border region for months?
Growing evidence in California suggests that early flu cases had no apparent origin in Mexico. Many of the early California victims — including the first two cases — say they hadn't traveled to Mexico and had no contact with pigs. Some may have fallen ill before the first Mexicans did.
Those cases contradict the conventional understanding of how the strain originated. They could also offer important clues about the future trajectory of the disease. Other cases here and in other states, as well as abroad, have clear links with Mexico.
Michael Shaw, associate director for laboratory science for the influenza division of the Centers for Disease Control and Prevention, said the flu theoretically could have appeared first in California, but he cautioned against drawing any conclusions since the strain also exhibited genetic characteristics traceable to Eurasia.
The first case discovered in California was a 10-year-old boy in San Diego County, who fell ill with a fever March 30.
Health authorities stumbled upon the case by chance. The boy had a throat swab taken at a clinic during a random check, a common procedure by health officials to monitor illness around the U.S.-Mexico border. "We got lucky," said Chavez.
Tests revealed the flu virus didn't match any typical human flu subtype. The CDC received samples April 14 and determined the cause to be the now well-known A/H1N1 influenza.