One of the two victims had been in contact with pigs. The other would have been contaminated by a relative who had been in contact with these animals, which suggests that the virus can be transmitted from person to person.
The Centers for Disease Control and prevention of diseases in the United States indicate that the new virus contains genes of swine influenza virus H1N1, which caused a worldwide panic two years ago, and elements of other viruses that have infected pigs during the last decade.
The children have been infected in July and August and have since recovered. The two had been vaccinated against influenza last year.
Officials are looking at other possible infections among participants at an agricultural fair in Pennsylvania. No further cases have been confirmed.