HOUSTON, Oct. 23 (Xinhua) -- Forty-six U.S. states and Washington D.C. are having widespread flu activities when production delays continue to hamper distribution of the A/H1N1 flu vaccine across the country, a leading U.S. health official said on Friday.

    "We are now in the second wave of pandemic influenza," Thomas R. Frieden, director of the federal Centers for Disease Control and Prevention (CDC) in Atlanta, confirmed at a press conference. "Forty-six states are reporting widespread activity," he added.

    Statistics released by the CDC on Friday show that the only states without widespread flu are Connecticut, Hawaii, New Jersey and South Carolina.

    Since the beginning of the H1N1 breakout in April and May, according to the CDC director, more than 1,000 deaths from the virus and more than 20,000 hospitalizations have been recorded around the country.

    A CDC survey released on Thursday found that one in five U.S. children had a flu-like illness earlier this month, and most of the cases were probably the H1N1 flu.

    "We expect that influenza will occur in waves. We can't predict how high, how far or how long the wave will go or when the next will come," Frieden said.

    As nervous Americans clamor for the N1N1 flu vaccine, production is running several weeks behind schedule because of the vaccine is growing more slowly in egg-based cultures than manufacturers had anticipated, resulting in fewer available doses.

    "As of Friday, there were 16.1 million doses on hand nationwide, up from 14.1 on Wednesday," Frieden said. "It's frustrating to all of us. We are nowhere near where we thought we would be by now. We are not near where the vaccine manufacturers predicted we would be."

    Because of production delays, the government has backed off initial, optimistic estimates that as many as 120 million vaccine doses would be available by mid-October.

    "What we have learned more in the last couple of weeks is that not only is the virus unpredictable, but vaccine production is much less predictable than we wish," he told reporters.

    The flu virus has to be grown in chicken eggs, and the yield hasn't been as high as was initially hoped, CDC officials explained. "Even if you yell at them, they don't grow faster," Frieden said.

    The widespread of the H1N1 virus epidemic plus the unpredicted delay of the vaccine are complicating the CDC strategy against the second wave of the epidemic.

    "Whether this will continue through the fall into winter, whether it will go away and come back in the winter, only time will tell," Frieden said.

Special Report:  World Tackles A/H1N1 Flu