What to Know about this Year’s Flu Season

If you haven’t had the flu this winter, you probably know someone who has.

From early October through late January, there were at least 22 million illnesses, 280,000 hospitalizations, and 12,000 deaths from flu in the U.S., according to CDC estimates.

And this year’s flu season is far from over.

To put those numbers into perspective: The relatively mild season of 2021-2022 saw 11 million illnesses, 120,000 hospitalizations, and 6,300 deaths, according to the CDC.

To help understand and combat this year’s flu season, Stephen S. Morse, PhD, professor of epidemiology at Columbia’s Mailman School of Public Health, discusses how flu spreads, why this year is worse, and what prevention habits work best.

What causes flu? What are the typical signs and symptoms?

The flu is caused by influenza viruses, most commonly influenza A and B, which are RNA viruses.

Typical symptoms include sudden fatigue and malaise, fever, muscle aches, cough, and feeling too weak to carry out normal activities.

Many people recognize flu because it “knocks you down” quickly; for otherwise healthy individuals, it usually resolves after several days.

How does flu spread?

Flu spreads mainly through the respiratory route, via particles released when infected people cough, sneeze, or exhale, which others then inhale.

It is also possible, but less likely, for the flu virus to enter the body through contact.

For example, touching a recently infected surface and then scratching one’s nose.

Why is this year’s flu so bad?

This season has been severe because H3N2 influenza A, which tends to cause worse illness, is circulating, along with a new variant (subclade K) that appeared late and is not well covered by current vaccines.

In addition, there has been lower vaccine uptake, meaning fewer people are getting immunized.

What’s more, there have been reduced precautionary behaviors since COVID-19, meaning habits like masking and avoiding crowds are less common.

What is the best protection against flu?

Protection against flu is not just one thing. Good protection includes several behaviors, including:

• Vaccination
• Masking in crowded or poorly ventilated spaces, or avoiding them
• Practicing good hand hygiene (washing your hands)
• Covering coughs and sneezes
• Staying home when sick

A lot of people don’t realize this, but the same measures that worked for COVID-19 also work for flu.

There would be many fewer flu cases if more people took it more seriously and behaved accordingly.

Are certain people especially vulnerable to flu? Would you recommend any additional measures?

Higher-risk groups include older adults, young children, pregnant women, and people with weakened immune systems or chronic medical conditions.

Beyond vaccination, they should avoid crowded indoor settings, wear masks, practice good hand hygiene, and seek early medical care if symptoms develop.

Is February too late to get vaccinated?

No, it’s not too late. While around October is best, it is still worthwhile to get vaccinated.

In the United States, flu season is generally considered to run from October through April or May, but infections usually peak in the winter.

February is often the highest peak month. The vaccine may not perfectly match every circulating strain, but it can still reduce severity, hospitalizations, and complications, and it can protect against other flu viruses that are circulating.