WASHINGTON - In the deadliest week yet for the nation's influenza outbreak, nine more children died of flu-related illness last week, bringing the season's pediatric death toll to 29, as officials nationwide continue to take protective measures to stop the spread of the virus.

At the halfway point of the 2012-2013 flu season, the number of child deaths has nearly matched the 34 that died in the mild 2011-2012 flu season, U.S. health officials said Friday.

More than half of the children who have died were not vaccinated and most had underlying health problems that made them more susceptible to the virus, said Dr. Tom Frieden, director of the U.S. Centers for Disease Control and Prevention.

But it's the elderly who continue to bear the brunt of the epidemic. Hospitalization rates for people ages 65 and over with laboratory-confirmed influenza jumped to 82 per 100,000 last week, from 70 per 100,000 the previous week, and about 50 per 100,000 during the last week of 2012. The overall hospitalization rate for the entire U.S. population was 19 per 100,000.

Frieden said the number of flu cases, as well as hospitalizations and deaths, are expected to rise as the epidemic progresses." "Seasonal influenza always takes the heaviest toll on seniors when it comes to deaths. In general, we estimate that about 90 percent of flu-related deaths are in people 65 and older."

Making matters worse, he said, health care providers aren't offering the antiviral medications, Tamiflu and Relenza, at appropriate levels to reduce patient suffering. After vaccination, both medications are viewed as the second line of defense against the flu because they shorten the duration of the virus and can cut the flu death rate by 50 to 75 percent when taken within two days of developing symptoms.

"Maybe as many as a third or half of people who are hospitalized with flu aren't getting prompt treatment with antivirals and that can have a big impact on reducing serious illness and death," he said.

Antivirals should be given to high-risk patients with flu symptoms even if rapid flu tests come back negative for the virus because of the prevalence of false negatives, Frieden said. High-risk patients include the elderly; infants and young children; and people with asthma, diabetes, heart disease, lung disease, neurological disorders and other underlying medical conditions.

Over a 25-year period, the number of U.S. flu deaths has varied annually from 3,000 to 49,000, said Dr. Joseph Bresee of the CDC's Epidemiology and Prevention Branch.