This year’s flu season is now more intense than any since the 2009 swine flu pandemic and still getting worse, federal health officials said on Friday. Nationally, the number of people falling ill with flu is increasing. More worrying, the hospitalization rate — a predictor of the death rate — has just jumped.
It is now on track to equal or surpass that of the 2014-2015 flu season. In that year, the Centers for Disease Control and Prevention estimates, 34 million Americans got the flu, 710,000 were hospitalized and about 56,000 died.
“We’ll expect something around those numbers,” Dr. Daniel B. Jernigan, director of the C.D.C.’s influenza division, said during a telephone news conference Friday.
This week, the deaths of seven children were reported to the C.D.C., bringing this season’s total to 37. In 2014-2015, there were 148 pediatric deaths — which the agency tracks individually, not by estimates as it does with death totals.
It is too early to estimate how many children will die this season, Dr. Jernigan said, because it still has weeks to run, and because the agency often does not learn of deaths — especially of children who die at home — until weeks after they take place.
Despite the late date, the agency still recommends that Americans get flu shots. Because some doctors and pharmacies have none left, Dr. Jernigan suggested checking vaccinefinder.org to find providers with stocks.
Some areas also have shortages of antivirals like Tamiflu, he said, and the C.D.C. is trying to help the supply chain move medicines to where they are needed most.
More people fell ill during the 2009 “swine flu” pandemic, but that was a new virus. This year’s dominant virus, H3N2, has been circulating for 50 years — it emerged as the “Hong Kong flu” in 1968 — but it is usually the most lethal of the seasonal strains.
H3N2 also was responsible for bad seasonal flu years in 1997-1998 and 2003-2004, Dr. Jernigan said.
As is typical, people over 65 are the most likely to be hospitalized. But in an unusual twist, those aged 50 to 64 — rather than infants — are the age cohort right behind the elderly.
“Baby boomers have higher hospitalization rates than their grandchildren right now,” Dr. Jernigan said.
Hospitalizations and deaths among people in that age group can hurt the economy more than deaths of the elderly, he noted, since they are in their peak earning years and often in supervisory positions.
They are also less likely to be protected. Recently, about 41 percent of that age group has gotten flu shots, while 57 percent of those over age 65 have; and the elderly usually get shots that are four times as powerful because their immune systems are weaker.
Despite the efforts of public health officials, the number of people getting shots each year has begun falling slightly.
The intense 2009 swine flu pandemic, which sent demand for vaccines soaring, was followed by several mild flu years. Then the “moderately severe” season of 2014-2015 was all but ignored by health reporters because they were focused on the Ebola outbreak in West Africa.
In this year’s outbreak, “flu intensity” — a measure of how many catch the disease — is now widespread, but hospitalization rates have varied widely by region.
California and the West Coast have been hit hard, with four times as many people hospitalized as in 2014-2015, Dr. Jernigan said. Minnesota had twice as many. New York and the Northeast “are beginning to catch up,” he added.
Intensity is high by two different measures the C.D.C. uses. For three weeks straight, the health departments of 49 states — all except Hawaii — have reported “widespread” flu activity.
Also, sentinel sites in 39 states, New York City and Puerto Rico are reporting “high” flu levels. (The sites include more than 2,000 emergency rooms, clinics and doctor’s offices that report each week what percentage of their patients have flu symptoms.)
According to the C.D.C.’s weekly FluView, 6.6 percent of all patients visiting doctors now have flu symptoms. The 2014-2015 season peaked at 6 percent, while the 2009 “swine flu” season peaked at 7.7 percent.
Three weeks ago, the C.D.C. thought cases had peaked during the week between Christmas and New Years Day. But they have climbed since, and Dr. Jernigan said it appeared to be due to “kids returning to school.”
Until recently, the severity indexes had languished behind the measures of intensity.
The agency’s national “Pneumonia and Influenza Mortality Surveillance Index” ripples like a sine wave, rising in winter and falling in summer. Until recently, the red line indicating deaths had remained firmly below the “epidemic threshold” even as the red line on a different index tracking doctor’s visits was following the pattern set by the 2014-2015 season with eerie exactness.
Then, two weeks ago, the intensity line plodded steadily beyond the 2014-2015 Christmas week peak, but the mortality line initially did not budge. But it is now shooting upward at the high trajectory angle of a North Korean rocket, has passed the peaks of the last two seasons and is on track to match or surpass 2014-2015.
This Flu Season Is the Worst in Nearly a Decade
By DONALD G. McNEIL Jr.JAN. 26, 2018
A version of this article appears in print on January 27, 2018, on Page A15 of the New York edition with the headline: This Flu Season Is the Worst in Nearly a Decade. Order Reprints| Today’s Paper |Subscribe