The US disease prevention center claims the newly-spread potentially-fatal strain of swine flu virus may have originated from California.
The Centers for Disease Control and Protection (CDC) said on Saturday that the state preceded Mexico, the alleged source of the virus, in reporting cases of the affliction.
“As we do our investigations here in the US, we may find that there were cases earlier,” CDC spokesman, Scott Bryan was quoted by AFP as saying.
As early as March, patients were diagnosed in California with a new type of viral infection resulting from the A(H1N1) — the new strain of the swine flu virus, H1N1 which is apt to affect humans and pigs and resist antiviral treatment.
The patients had neither been to Mexico nor had they come into contact with pigs.
San Diego County and California County were the first to report sufferers in late March, The Wall Street Journal reported.
12 suspects had also tested positive for a strange strain from December 2005 to January 2009, Bryan added.
About 160 lab-confirmed cases have been reported in 21 US states with one leading to death. Two-thirds of the patients had not had any contact with Mexico.
As the disease crawls along in Europe and Asia after the Americas, Mexican health authorities claim they have been partially successful in stemming the contagion.
Ireland is the latest to report a case of swine flu. Infection with the virus has also been confirmed in Canada (51), Spain (15), Britain (13), Germany (6), New Zealand (4), Israel (3), Costa Rica (2), France (2), Austria (1), Benin (1), Denmark (1), Hong Kong (1), Netherlands (1), South Korea (1) and Switzerland (1).
The World Heath Organization (WHO) is considering raising the pandemic alert level to phase 6 — the highest level and an indication of a global outbreak of the swine flu.