Citing a study scheduled to be released later this week, Dr. Thomas Frieden, the chief of the US Centers for Disease Control and Prevention (CDC), said on Sunday that new H1N1 swine flu - Influenza A - infected approximately 800,000 people in New York City last spring.

Frieden - who was New York City's health commissioner, prior to his appointment as the CDC head in June - said that surveys clearly suggested that the city was in the grip of the virus; which, as per the World Health Organization (WHO), directly affects the lungs and causes severe illness in healthy young people and necessitates costly treatment.

While the complete study and comprehensive statistical analysis is expected by the New York City health department officials within a few days, Frieden noted that there is apparently a twenty-fold discrepancy in terms of H1N1 infections around the US. Frieden said: "We expect that some places will have more flu. Some places will have less."

In fact, with more than 1 million people in the US affected by swine flu, and nearly 10 percent of New York City residents being hit, combating the virus is clearly CDC's top priority at the moment - more so as H1N1 reportedly spreads four times faster than any other viruses, and 40 percent of the fatalities are healthy young adults.