Pennsylvania's flu season among mildest ever

Pennsylvania had one of its mildest flu seasons on record, with high flu vaccine rates and mitigation measures aimed to slow the spread of covid-19 keeping influenza cases low, officials said Friday.

This year’s flu season, which officially ended May 22, saw 3,664 lab-confirmed cases statewide, according to Deputy Secretary of Health Preparedness and Community Protection Ray Barishansky.

That marked a 95% decrease from cumulative case counts at the end of last year’s flu season.

“The previous season was higher than usual, with more than 130,900 cases of flu,” Acting Secretary of Health Alison Beam said.

There were 21 flu-related deaths in Pennsylvania this year and 45 hospitalizations.

Barishansky compared this year’s mild flu season, as covid-19 circulated simultaneously, with the 2015-16 flu season, when the H1N1 flu virus was predominant.

While both Influenza A and Influenza B were identified in every county in Pennsylvania, more than one-third of counties reported fewer than 10 cases of the flu this season, and flu cases remained below the state epidemic threshold.

These low flu numbers came despite increased testing, Barishansky said.

“Across the nation, there was a sixfold increase in testing at public health labs, most of which test for Influenza A and B along with covid-19. Even so, there was a drop in flu cases nationally,” he said.

The Department of Health and the federal Centers for Disease Control and Prevention recommended that health care providers test for both viruses patients who presented symptoms consistent with the flu or covid-19. Because of the testing recommendations, Barishansky said he “did not believe it was possible” that individuals with the flu were incorrectly counted among covid-19 cases instead.

“The CDC recommended health care professionals test people who have covid-19-like symptoms for both flu and covid-19 because it is impossible to differentiate between the two viruses without testing, and patients can have both viruses at the same time,” he said.

He declined to provide information regarding how the number of individuals tested for the flu compared to the number of individuals tested for covid-19, saying it was impossible to compare the testing numbers because covid-19 is a new infectious disease.

One reason for the low levels of influenza this year, he said, was the record-breaking vaccine uptake. As of February, the CDC reported 193.8 million doses of flu vaccine had been distributed in the United States, surpassing the previous record of 174.5 million flu vaccines in the 2019-20 flu season.

Measures meant to curb the spread of covid-19, such as mask wearing, social distancing and heightened cleaning and sanitizing, also contributed to a mild flu season, Barishansky said.

“The low flu activity, in part, is a testament to effective covid-19 mitigation efforts that also prevent the flu,” he said, encouraging good health habits like covering the mouth and nose when sneezing, frequently washing hands and remembering to disinfect high-touch surfaces.

“Practicing these healthy habits, plus covid-19 safety measures such as getting the covid-19 vaccine, wearing masks and responsibly social distancing, were all factors that kept our flu case count low,” he said, urging Pennsylvanians to continue emphasizing such habits.

Dr. Amesh Adalja, a Pittsburgh-based infectious disease expert and senior scholar at the Johns Hopkins Center for Health Security, also pointed to covid mitigation measures as likely causes for a mild flu season. He noted that the interruption of schooling for children, who he said “tend to amplify influenza,” also may have helped slow the spread of the flu this year.

Though measures such as masking were emphasized this year during the covid-19 pandemic, Barishansky said he can’t predict whether they will become ubiquitous in future flu seasons.

“I can’t speak to whether we would mandate mask wearing for upcoming flu seasons,” he said. “I believe we’ve learned a lot of lessons in regard to public health actions as we move forward.

“Some of those lessons include masking up when you’re symptomatic, or potentially masking up when you’re in a public place and symptomatic, washing your hands, utilization of hand sanitizer, even social distancing in specific circumstances.”

Adalja said although he anticipates some of the behaviors people have adopted during covid-19 will stick around, it is impossible to say what the next flu season will look like.

“I suspect some of the behaviors people adopted for covid will continue to be part of some people’s routine next flu season and have benefit,” he said. “However, the next flu season is a bit of a mystery, as the seasonal viruses are circulated at such low levels in both the Northern and Southern hemispheres that it’s hard to predict what will happen.”