Sixteen children died from the flu over the past week as the number of Americans hit by an already record-setting flu season continues to rise and hospitalization rates hit new highs, the Centers for Disease Control and Prevention said today.

Hospitals are more crowded than in the 2014-2015 flu season, which held the previous record when 710,000 Americans needed medical care to beat the illness, said Anne Schuchat, the CDC’s acting director. The agency also reported that the deaths of the 16 children over the past week brings the total number of pediatric deaths attributed to the flu to 53 so far this season. Half of them had no other health complications that would have placed them at elevated risk, Schuchat said.

“This season is a somber reminder of why flu is one of the world’s biggest health challenges,” she said in a conference call. “Our latest data indicate flu is still high and widespread across most of the nation—and increasing overall.”

“We do not know if we have hit the peak yet,” Schuchat said. ”And many measurements are still going up.”

The relentless outbreak has led politicians in several states to reach out directly to constituents and urge them to take action to stall the spread, reaffirming the message from medical experts that everyone should get a flu shot. There was a 50 percent rise in people affected last week in New York, where there was a record 11,683 new cases and 2,221 people admitted to hospitals. Governor Andrew Cuomo called on New Yorkers to get the flu shot Thursday, more than two months after the influenza season began in earnest.

“Flu season is in full-swing, and as the number of influenza cases and hospitalizations continue to rise at alarming levels, we must take every action to protect ourselves and our loved ones,” Cuomo said.

It can take up to two weeks for the immunization to kick in, and there’s no guarantee of protection. The most optimistic studies have reported that this year’s vaccine will protect only 1 in 3 people, but its true effectiveness won’t be known until after the season is over. On Thursday, Canadian researchers found that the flu shot is only about 17 percent effective at preventing illness from the resilient H3N2 strain, the primary virus this season, and only 10 percent effective for those between the ages of 20 and 64.

Schuchat added that other strains are spreading too, including B virus and H1N1, and that the vaccine is more effective in beating those back.

No one knows exactly how long the unexpectedly potent and persistent H3N2 strain will linger. There are some signs that the outbreak may be easing in the west, which has been particularly hard-hit, though it continues to spread in the rest of the country.

“There is a little good news,” Schuchat said. “There are signs that activity in the west may be easing up. However, we are by no means out of the woods. We probably have several weeks left of flu activity.”