During past two months, the United States has witnessed two new cases of swine flu bug among humans, although both the victims, an Indiana boy and a Pennsylvania girl, have recovered from the illness.

In a release, the U. S. Centers for Disease Control and Prevention researchers have revealed that the kids had suffered flu viruses that are believed to be originated in pigs, and extracted the genetic material from influenza A H1N1 virus pandemic observed in 2009.

While briefing about the issue, Tom Skinner, a CDC Spokesman, said: "They are constantly changing, and that is why we have to have really good surveillance systems in place to detect them when they do emerge”.

In addition, Tom Skinner has claimed that there are least chances that can offer a feasible environment to pass the virus to humans easily although, notified that CDC investigations are in progress .

Sources have revealed that out of recent cases, the Indian boy has received flu vaccine during last September, consequent to deadly flu symptoms including fever, cough, diarrhea, a sore throat and difficulty in breathing developed in July.

Afterwards, he was admitted in the emergency department where tests have confirmed his influenza A virus infection.