The CDC is testing both viruses to make sure they can stimulate an optimal immune response, Schuchat said. Food and Drug Administration, has also created a second candidate virus using reverse genetics, Schuchat added. The strain was created by "combining the genes of the novel H1N1 virus with other parts from other viruses," Schuchat explained. This type of hybrid virus will grow more easily in eggs -- an essential part of the vaccine production process. Meanwhile, a 50-year-old woman died of swine flu in New York City over the weekend, becoming the second swine flu fatality in that city and the 11th in the United States, according to. Lusa Schuchat, the CDC's interim deputy director for science and public health program, said during a news conference on Friday.

But good news came from CDC officials, who reported that they are closer to a viable vaccine for this new strain of flu.

No other information on her alphonso was disclosed Sunday. As with most of the other reported swine flu deaths, the woman had other health conditions, Department of Health and Mental Hygiene spokeswoman Jessica Scaperotti said.

"Today CDC received, from one institution, a candidate vaccine virus," Dr.