Dear Doctor: I have a question I’m sure is on the minds of others, as well -- where is the flu this year? All we are hearing about is COVID-19. Did the flu vaccine they gave work that well? Is no one getting the flu anymore?
Dear Reader: You’ve asked an excellent question with a somewhat complex answer. The short version is that, yes, incidence of influenza infection has been markedly lower for the flu season thus far. We’re seeing that in our own practices. As of the middle of February, we have not had a single case of influenza. To say that’s unusual is an understatement.
Our experience is reflected in the numbers that the Centers for Disease Control and Prevention use to track the course of influenza infection in the United States. In the last week of 2020, for example, only 1% of samples tested positive for influenza. Typical results at that time of year are in the 20% to 30% range. Global tracking data also mirror this trend.
A number of factors are playing a role in this year’s surprising flu season numbers. An important one is the many mitigation measures we’re all taking in the fight against COVID-19. These include social distancing, wearing a mask, vigilant hand-washing and cleaning high-touch surfaces. Environments that act as natural petri dishes for the spread of respiratory infections, such as offices and classrooms, are either severely restricted or completely shut down. Ditto for group activities such as concerts, sporting events, travel, dining, bars and other recreational activities. In physically protecting ourselves and limiting our potential exposure to the airborne coronavirus, we’re also shielding ourselves from the coughs and sneezes and surface contamination that spread the flu. The influenza virus, less transmissible than the coronavirus, is proving no match for these multiple layers of precautions.
The differences in tracking methods for COVID-19 and the flu are playing a role. With the coronavirus, the goal is to count every possible case in order to understand the trajectory of the pandemic. To that end, many millions of coronavirus tests have been administered, and all of the resulting data collected and logged. Statistics about the number of cases each flu season, by contrast, are estimates. These are arrived at by analyzing testing data collected from designated public health and clinical laboratories, and from a network of medical practices and hospitals.
It’s also important to note that people aren’t visiting the doctor as much as in pre-pandemic days. When they do seek medical care, the respiratory illness they’re most concerned with is COVID-19, so that’s the test they’re most interested in getting. There’s evidence that a number of people are opting to treat suspected flu-related illnesses at home, which also lowers the reported influenza numbers. However, influenza-related hospitalization rates, with just 155 lab-confirmed admissions from Oct. 1, 2020, to Jan. 30, 2021, bolster the idea that this year’s flu season is unusually mild.
If mask-wearing and other physical precautions continue after the epidemic, then we may continue to see lower influenza rates in the future.
(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)
