The number of influenza cases in the Philadelphia region is higher than usually seen at this time of year, mirroring an uptick being reported across the country.
These flu cases also are more severe, according to the U.S. Centers for Disease Control and Prevention. The national hospitalization rate is the highest it has been at this point in the fall since the 2009 H1N1 swine flu pandemic.
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There already have been an estimated 880,000 influenza cases, 6,900 flu-related hospitalizations and 360 flu-related deaths this flu season, according to the CDC's weekly flu season report. The southeast, south-central and New York are experiencing the highest levels of activity.
Flu season usually runs from October through May, typically peaking between December and February, but this season started about six weeks earlier. Some health experts say this early start may portend a tough flu season, but they caution that flu seasons are unpredictable.
In Philadelphia, the number of influenza-like illnesses among children is higher than what was seen at this point last season. Local hospital laboratories also have indicated a steady rise in influenza A detections, according to the city health department.
"It's impossible to say at this point if this is a harbinger of a bad year," James Garrow, spokesperson for the health department, said in an email. "It's starting early than usual, but it's impossible to say what will happen once we get into the more traditional flu months."
The last two flu seasons have been generally mild – an outcome partly attributed to the protective measures implemented in response to the COVID-19 pandemic.
But this year, influenza season started early in the southern hemisphere, where flu season generally runs from May to October. Scientists often look there for hints on how the U.S. flu season might unfold. Though Australia had an early and busy flu season, the number of intensive care admissions and deaths were low.
Still, Lynnette Brammer, team lead for domestic surveillance in the CDC’s influenza division, told STAT that it's impossible at this point to know how bad this season will be.
"What a lot of people are implying is because it's early and levels are high for this time of year that it's going to be a severe season. We don't know that," she said. "Right now all we can say is we're off to an early start."
Across Pennsylvania, seasonal flu activity remains relatively low, although it is higher than was what has been seen during the last five years. There have been 2,480 lab-confirmed cases reported, including 168 in Philadelphia, this season, according to the Pennsylvania Department of Health. The percentage of emergency department visits for flu-like illness is low; there has been one confirmed flu death.
New Jersey is reporting a moderate level of flu activity statewide, with 1,682 cases, according to its weekly flu report. Emergency department and doctor visits for flu-like illnesses are higher than they were at this point last year. An outbreak has been recorded at a long-term care facility.
Additionally, hospitals across the country also are seeing large numbers of cases of respiratory syncytial virus, another respiratory illness that usually hits an upswing in the winter.
One of the biggest concerns is that people's immune systems may not be prepared to fight off influenza because so little of the virus has circulated in the last two years. More people may be vulnerable to severe illness, particularly with fewer people masking or practicing social distancing.
"The past two very mild flu seasons have spoiled us," Dr. William Schaffner, an infectious-disease specialist at the Vanderbilt University School of Medicine in Nashville, Tennessee, told Everyday Health. "This year we've taken off our masks; we're traveling, visiting friends and relatives, attending religious services, and our children are back in school. All these activities provide an opportunity for the flu virus to spread easily."
This year's flu vaccine appears to be well-matched against the influenza strains circulating, according to a report from Chile published in the CDC's Morbidity and Mortality Weekly Report. In Chile, health officials estimated that the flu vaccine efficacy was 49% against H3N2 viruses, the strain that is causing the most disease in the U.S.
As of October 15, 128.4 million doses of the flu vaccine have been distributed in the U.S. Health officials are encouraging anyone who is eligible to get a flu shot as soon as possible. If the flu continues to circulate at its current level of activity, they expect there will be a lot of respiratory illnesses around the holidays.