US Centres for Disease Control and Prevention officials said there's no reason for the public to take unusual measures against it.
Health officials have long feared the emergence of a deadly form of flu. They have not noted a spike in flu cases or a rash of severe illnesses. But they are continuing to investigate the genetics of the virus and track down and test people who may have been in contact with the children.
Both children became sick in late March and experienced fever and cough. The boy also vomited. The two had not been in contact with each other, CDC officials said. Both have since recovered.
Human swine influenze cases
In the past, CDC received reports of approximately one human swine influenza virus infection every one or two years. But more than a dozen cases of human infection with swine influenza have been reported since late 2005.
Most cases occur in people who were exposed to pigs, but in this case neither child had touched a pig, according to their families. The jump in cases in the past few years could be because of technological improvements and expansion of public health laboratories, which have improved testing capacity. But genetic mutations could also play a role.
The same virus has not been detected in any California pigs. "But we don't test every pig for influenza, so we don't know all the strains that are circulating," said Dr. Gil Chavez, California's state epidemiologist.
