A sign at the entrance of Central Maine Medical Center in Lewiston in 2020 warns about the dangers of the influenza virus. Statistics on the flu from the Maine CDC show that the COVID-19 pandemic played a significant role in the decrease of confirmed cases over the last two years.  Russ Dillingham/Sun Journal file

There are several unknowns ahead as flu season officially begins in Maine this month, the third season since the pandemic began.

The Maine Center for Disease Control and Prevention will begin issuing weekly surveillance reports and continue to do so until it switches to monthly reports next May or June, which is usually the off-season for flu in Maine.

Maine typically does not see a peak in cases until December or January, Dr. David Baker, a pediatrician at Central Maine Pediatrics in Lewiston, said in August.

But since the pandemic began two-and-a-half years ago, Maine’s flu season has been anything but typical.

The Maine CDC recorded between 9,000 and 10,500 laboratory-confirmed flu cases total for each season that began in 2017, 2018 and 2019, according to weekly surveillance reports.

During the season that began October 2020 and ended September 2021, Maine officially recorded only 208 flu cases across the state. That’s fewer cases than Maine recorded in a single week in prior years.

The answer for why flu cases declined dramatically may be found in the weeks following when Maine went into lockdown in March 2020. That season, new weekly cases peaked in mid-February, with over 900 new cases reported.

During the week ending March 14, 2020, there were 700 new cases. The following week, just over 400.

By the end of the first week of April, the Maine CDC had recorded just 15 new cases.

“The decrease in influenza circulation seen since the beginning of the COVID-19 pandemic was likely due to COVID-19 mitigation efforts such as masking, physical distancing, and staying home when sick,” said Anna Krueger, a Maine CDC epidemiologist who specializes in influenza.

“We know that the number of influenza tests performed by several large laboratory facilities were at the same levels, and sometimes higher, than pre-pandemic seasons, suggesting the decrease in influenza cases was not a result in decreased testing,” she said.

Flu-associated deaths and hospitalizations, as well as emergency room visits, continue to be much lower over the past two years compared to pre-pandemic.

There were just four flu-associated hospitalizations and no deaths during the 2020-2021 season, for example. The season prior, there were 517 hospitalizations and 42 deaths.

It’s still impossible to say definitively that the sharp drop in cases in the spring of 2020 was due to mitigation efforts or because many people were avoiding going to a doctor’s office, where they would get tested for the flu, Krueger said.

“Though we may never know, we do know that the levels remained lower for the remainder of the 2020-2021 season and the 2021-2022 season, during which time influenza testing levels returned to pre-pandemic levels,” she said.

Nationally, the 2021-22 flu season “peaked later in the season than any other influenza season on record,” Krueger said. In Maine, cases peaked in May.

“It is thought that this may have been influenced by the interruption of influenza circulation since the start of the COVID-19 pandemic. Influenza and many other respiratory viruses have not yet gotten back to pre-pandemic circulation patterns.”

Baker, the pediatrician, said he’s seen that at his practice. When he spoke to the Sun Journal just before the school year began in August, he noted this “whole shift, seasonal shift, of infections (that) has occurred,” with the flu being “probably the prime example.”

Around the same time last year, Dr. Gretchen Pianka, also a pediatrician at Central Maine Pediatrics, told the Sun Journal “we are definitely seeing a very strange season for viruses in general.”

She was seeing a lot of children who came in with several co-occurring viral infections “that don’t usually overlap.”

“The only thing that I can think of from kind of the public health standpoint is that we started seeing all of this when everybody had started moving around more, stopped masking, stop doing all of the careful precautions that we were doing during the height of the COVID pandemic,” she said.

“So when everybody was being really careful, we were seeing hardly any viral illnesses in the kids. And then everybody started kind of moving around and doing more relaxed precautions, and then we’re seeing a lot of viral transmission in unusual ways,” Pianka said.

The coming weeks will be telling for the flu season, Baker predicted in August. Usually, the first few weeks of the school year have an “eerie quiet,” he said. “But then, give it about three or four weeks and then the floodgates open.”