How to Spot Serious Flu Symptoms

Some can be atypical in older adults. Spotting them can be key to getting an effective antiviral Rx

Kimberly Goad,

AARP

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En español

Published September 10, 2021

/ Updated September 08, 2023

pattern of thermometers used to take a person's temperature

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Fever. Fatigue. Muscle aches. A cough. In the age of COVID-19, it can be hard to know what exactly these symptoms point to. One major clue that they point directly to the flu: They came on abruptly (while those associated with COVID-19 tend to start out mild and gradually worsen).

But that’s not to say the flu always announces itself in the regular way — particularly among people over 65. In a study published in the Journal of the American Geriatrics Society, older patients were less likely than younger ones to report fever, cough and sore throat — arguably the most common flu symptoms — and as a result, weren’t diagnosed as quickly, if at all. That can be problematic if you’re 65 and older, since age alone ups your chances of getting hit much harder by a bout with the flu.

Blame your immune system, which weakens with age, “so all infections are more severe, as are complications from infections,” says infectious disease specialist Purvi Parikh, M.D., a clinical assistant professor in the department of medicine at NYU Grossman School of Medicine. “Those over 65 may also have other chronic medical problems like heart disease and diabetes that make it even harder to fight off infections."

That explains why 70 to 85 percent of seasonal-flu-related deaths have occurred in people 65 and older; and 50 to 70 percent of seasonal-flu-related hospitalizations have happened among older adults, according to the Centers for Disease Control and Prevention.

“There’s always been clear knowledge that people over 65 are at an increased risk of severe complications from influenza, and hospitalization or death,” says Paul Auwaerter, M.D., clinical director of the division of infectious diseases and professor of medicine at the Johns Hopkins University School of Medicine. That’s why it’s important to get up to speed on flu symptoms and see your doctor if you have any or all of the following, especially if you have a medical condition such as heart disease or diabetes.

1. Fever

All kinds of things can make your body temperature venture north or south of the well-known benchmark of 98.6 F. For instance, it can go up when you exercise and down when you sleep. But a fever of 100.4 F or more is “a sign your body is responding to something dangerous physically and is trying to mount an immune response,” says Auwaerter.

But a fever doesn’t have to get that high to cause complications in people over 65, he adds. Why? “People who are older may have less buffer in terms of handling fever and the infection may worsen more rapidly than it might in a younger person,” he says.

“Any fever in an elderly person is a red flag,” Auwaerter stresses, adding that you should call your doctor if you have a temperature over 100 F. If you’re under 65 and do not have any other risk factors, you might have uncomplicated influenza, he says, which could respond well to over-the-counter therapies and supportive care.

Keep in mind: Just because you aren’t running a temperature doesn’t mean you’re in the clear. You can have the flu without having a fever.

2. Trouble breathing

You’re short of breath and all you’ve done is walk to the mailbox and back. Or maybe you’re having trouble completing a sentence without stopping to catch your breath. A family member may even have noticed you’re breathing faster than normal. If you have the flu, all of these can be a red flag that your condition has become serious.

“When you’re not getting enough oxygen, the body sends out signals to breathe fast in an effort to increase oxygen levels and adrenaline levels to make the body respond to a relative state of not acquiring enough oxygen that’s demanded by the body,” explains Auwaerter. “If you’re feeling short of breath, if you’re turning blue, if you’re confused — all of these should prompt calling emergency medical services.”

3. Dehydration

Staying hydrated is always important. If your body isn’t getting enough fluids, it can’t function as it should. And yet research suggests 17 to 28 percent of older adults in the U.S. are dehydrated for any number of reasons. Not only is it a frequent cause of hospitalization, it can also complicate various medical conditions.

There are a number of ways the flu can make it difficult to stay hydrated. If you’re running a fever, vomiting or have diarrhea, it’s easy to become dehydrated, notes Auwaerter. “Breathing faster than normal also causes water losses.”

That’s why getting plenty of fluids (water, broth, sports drinks) is critical to avoiding complications from the flu. Just don’t wait until you’re thirsty to drink. Although mild fluid loss can usually be treated at home, severe dehydration must be treated in the hospital, according to the CDC.

Some signs you’re dehydrated: Besides extreme thirst, look for fatigue, dizziness, confusion, a fast-beating heart, dry eyes and dark-colored urine. “I tell people to drink enough so they’re going to the bathroom regularly and their urine is light-colored to clear,” says Auwaerter. If you have heart failure or kidney disease, check with your doctor about safe amounts of liquid.

And don’t forget: Alcohol and caffeinated drinks aren’t fluids you should be reaching for when you’ve got the flu. These act as a diuretic, just the opposite of what you should be consuming when you’re trying to stay hydrated.

4. Dizziness or confusion

When you have the flu or another infection like COVID-19, a sudden and significant change in health status should be considered a red flag. You should contact your doctor right away or go to the emergency room if they occur during a bout with respiratory illness, says Waleed Javaid, M.D., director of infection prevention and control at Mount Sinai Downtown and professor of medicine, infectious diseases, at the Icahn School of Medicine at Mount Sinai in New York. “Persistent dizziness or confusion could be a sign of severe illness, dehydration or lack of oxygen,” he notes.

Getting Early Treatment With Antivirals

When it comes to treating the flu, time is of the essence. You typically have two days from the onset of symptoms to start taking an antiviral drug — a type of prescription medicine that keeps the flu virus from replicating in your body. Antiviral treatment can be the difference between having a milder case of the flu versus a more serious bout. Some studies have reported that when used early enough, it can reduce the risk of death for adults hospitalized with the flu.

“Anyone who thinks they have influenza should call their doctor, because early treatment is paramount to getting better, and there’s a limited window after onset of symptoms for antivirals to work,” says Auwaerter of Johns Hopkins. “Patients with risk factors or progressive symptoms of influenza have a longer period for which antiviral medicines may have some impact, even three to four days into their illness,” he adds. But sooner is better “to avoid severe illness or hospitalization.”

Your doctor will take into account your overall health when prescribing one of the four antivirals recommended by the CDC to treat the flu:

oseltamivir phosphate (Tamiflu)

One of the oldest antivirals on the market, this is taken as a pill or liquid suspension and is also available as an equally effective, and often cheaper, generic medicine. Clinical trials have proven that this drug works to relieve flu symptoms.

zanamivir (Relenza)

Taken through an inhaler device, this drug isn’t recommended for people with breathing problems such as chronic obstructive pulmonary disease (COPD) or asthma.

peramivir (Rapivab)

Given intravenously, this antiviral is used for hospitalized patients.

baloxavir marboxil (Xofluza)

One of the newest antivirals available, it can be taken as a single dose (as opposed to Tamiflu, which is taken over several days). Given its side effects, however, this medication is not recommended for people with other illnesses, or those whose immune systems are severely compromised.

Editor’s Note: This story, originally published Sept. 10, 2021, has been updated to reflect new information.

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Kimberly Goad is a New York-based journalist who has covered health for some of the nation’s top consumer publications. Her work has appeared in Women’s Health, Prevention, Health and Reader's Digest.

How to Spot Serious Flu Symptoms​