The bad news is that a different strain of the H1N1 flu is expected to hit to the United States this fall with a vengeance, but the good news is that researchers expect to have a vaccine of two or more doses ready for public use in October.

"It's not over. In the U.S. it is persisting through the summer. The estimated number affected is about 1 million cases," Capt. Sonja Hutchins, M.D., MPH, Dr.PH. said of H1N1. "In the fall, we are expected to have seasonal influenza as well as H1N1."

Dr. Hutchins, senior medical officer, epidemiology, and officer of minority health and disparities for the Centers for Disease Control, presented "H1N1: The First Pandemic of the 21st Century" July 29 during NMA Internal Medicine Section's Infectious Disease Update.

H1N1 presents great challenges for the health care community and researchers trying to develop a vaccine because the flu is very transmissible and has antiviral resistance patterns that have made existing medications ineffective, she said.

"The vaccine will be effective, but we don't know how effective it will be," Dr. Hutchins said, adding that it may be difficult to produce enough of the vaccine for everyone and that it is still not known how many doses of the vaccine will be needed.

U.S. health officials are working to establish priorities for who will receive the vaccine, as well as other details, she said.

What is known is that H1N1 has changed since it appeared in North America earlier this year, late in the flu season.

"It has remarkable heterogeneity and has affected young people disproportionately. Most of those affected are less than 24 years of age. There is severe disease with this strain," Dr. Hutchins said, adding that in June the World Health Organization labeled the spread of H1N1 a pandemic, with 70 countries reporting cases.

In response, the U.S. government has mounted an aggressive response with enhanced surveillance, vaccination research, community measures and effective communication, she said. It is tracking when and where influenza activity is occurring as well as influenza-related illness.

As fall approaches, reports on H1N1 will increase from weekly to daily, and mortality reports from 122 cities and lab reports of isolates will be tracked, Dr. Hutchins said.

While developing a vaccine is a priority, the government is also focusing on a distribution program, which could include physicians giving vaccinations and being reimbursed for administrative costs, she said.

Also important are community measures to keep healthy students and workers in their normal routines while those who are sick stay at home. This could include a school dismissal system, so Dr. Hutchins said to "stay tuned," emphasizing that Mexico had great success controlling the spread of H1N1 by recognizing its dangers early and limiting large gatherings at the peak of the disease.

Finally, individuals should know they could help by washing their hands with soap and water, and avoiding touching surfaces that could be infected, she said.

"This is a shared responsibility," Dr. Hutchins said. "We have to work closely with local health agencies. The vaccine will go to local health agencies, so there needs to be a lot of communication back and forth."