by Carol J. Bova

The 2020-2021 flu season began with the week ending October 4 – Week 40.  “There have been 2 infections in Virginia during the 2020-21 flu season to date,” the Virginia Department of Health (VDH) said on December 17. By comparison, last year Virginia experienced sporadic cases from weeks 40 through 44, local occurrences in Weeks 45-46, and jumped to widespread cases from Week 47 of 2019 into April of 2020.

According to reports from the Centers for Disease Control (CDC), this flu season, after more than 469,000 tests, there are only 789 recorded cases and 168 deaths in the entire country. News reports in mid-December noted the unusual pattern of low influenza numbers and speculated on the reasons.

• Nature.com, December 15: “Measures meant to tame the coronavirus pandemic are quashing influenza and most other respiratory diseases, which could have wide-ranging implications. …Conversely, some common-cold viruses have thrived, and tantalizing evidence suggests that they might, in some cases, protect against COVID-19.”
• HealthLine.com, December 16: “Even though flu activity is low, and overall vaccination rates are strong, the flu is out there and could surge at any moment.”
• ABCNews.go.com, December 18: “Flu numbers are down this year due to higher vaccination rates amid COVID pandemic. Experts say mask use and social distancing have also helped keep numbers low.”
• USAToday.com, December 19: ”Fact check: Flu activity is low so far, likely because of pandemic precautions.”

The CDC said that outpatient illness “remained at 1.6% for the fourth consecutive week…below the baseline of 2.6%” and pointed out that the flu surveillance might be impacted by the COVID-19 pandemic. In a CDC internet survey in September, 2020, 59% of the respondents said they had received or planned to get the flu vaccine. Last year 52% said they would, and 49% of the public actually did receive the vaccine. But that relative increase doesn’t seem to account for how low the influenza numbers are now.

If COVID-19 precautions are responsible, why were there 1,203 influenza deaths for the weeks ending April 12, 2020 to September 26, between the 2019-2020 and 2020-2021 flu seasons?

We won’t have answers for the low numbers for quite a while, but here are the CDC national facts so far and comparisons to prior years.

The CDC takes two years after the flu season ends to determine the final influenza incidence and mortality numbers. In the meantime, they offer a page with “Past Seasons Estimated Influenza Disease Burden” since 2010-11 with preliminary range of cases, hospitalizations and deaths covering a 95 percent uncertainty interval (95% UI).

For the past two seasons, as of October 1, 2020, the numbers were:

2018-2019, October to May
Illnesses: between 31 and 45 million
Hospitalizations: between 390,000 and 770,000
Deaths: between 26,000 and 53,000

2019-2020: Weeks ending October 1 to April 4
Illnesses: between 34 and 47 million
Hospitalizations: between 350,000 and 500,000
Deaths: between 18,000 and 29,000

2020. But on another page, updated December 3, 2020, the 2019-2020 numbers saw a dramatic rise upward:
Illnesses: between 39 and 56 million
Hospitalizations: between 410,000 and 770,000
Deaths: between 24,000 and 62,000

For the current year, the COVID pandemic has interfered with normal data collection, and the CDC says “levels should be interpreted with caution.” That interference in the early months of the pandemic may explain the recent revision of the 2019-2020 numbers.

For the official season:

2020-2021 Weeks Ending October 4 to December 12, 2020
Specimens tested:

Clinical Labs: 286,984
Public Health Labs: 182,414
Illnesses: 789
666 confirmed by U.S. Clinical Labs
123 confirmed by U.S. Public Health Labs
Hospitalizations:  75
Influenza Deaths: 168

Pneumonia, Influenza and/or COVID-19 in the National Center for Health Statistics Mortality Surveillance System Chart, for Flu Season Weeks Ending October 4 to December 17, 2020:

Pneumonia Deaths: 61,690
Influenza Deaths: 168
COVID-19 Deaths:  73,981
Pneumonia, Influenza or COVID Deaths: 100,729
All Deaths: 601,229