Why the Flu is Often Missed in Older Adults
(& What to Do About This)

You’ve likely already heard the news: the flu is pretty bad this year, with the Centers for Disease Control (CDC) confirming a higher than usual level of illnesses, hospitalizations, and even deaths.

You also probably know that older adults (and certain other groups of people) have a higher risk of falling very ill from the flu, and have the highest death rates from flu.

But what many people don’t know is this: influenza is easily — and often — missed in older adults.

What do I mean by missed? I mean:

• Older adults (or their family members) may not realize an older person has the flu, because many older people don’t develop “typical” influenza symptoms.
• Health professionals often fail to test older people for influenza, even when they are sick enough to be hospitalized. This phenomenon was confirmed in a recently published study.

This is a very serious issue, especially when the flu virus is causing a lot of severe illness, as it is now.

The main problem is this: delayed — or entirely missed — recognition of influenza means that older adults often don’t get treated early — or at all — with anti-influenza drugs such as oseltamivir (brand name Tamiflu).

Particularly for those older adults who have chronic illnesses (especially those affecting the heart or lungs) or are frail, you don’t want to miss that chance to take anti-influenza drugs. They can’t guarantee an older person will avoid a hospitalization or death from influenza, but they do improve one’s chances.

And anti-influenza drugs are most likely to work when they are given within 48 hours of a person falling ill from influenza, with earlier being better.

So when flu activity is widespread, families need to be prepared to recognize potential flu.

And, you should be prepared for the possibility that the health providers might not think to test for influenza, unless you ask about it.

This article will help you learn to do these things. Here’s what I’ll cover:

• What are the usual symptoms of “influenza-like illness”
• Common symptoms of influenza in older adults
• Why older adults may not show typical influenza symptoms
• What we know about older adults & influenza testing
• What the CDC currently recommends, regarding influenza diagnosis and treatment
• What to do, if an older person falls ill during influenza season

You may also want to see this related article, which explains some influenza basics in more detail: Flu Shots for Older Adults: What to Know & Do.

And in case you are wondering: if you have not yet been vaccinated for the flu this season, it’s not too late. The flu is often active well into the spring (e.g. March, April, or even sometimes May). As I note in the article on flu shots, older adults will probably get better protection from the vaccine if they get the high-dose flu shot. Use VaccineFinder.org to find a flu vaccine near you.

Now let’s go into how you can recognize the flu in an older person.

What are the usual symptoms of influenza?

Here’s how the CDC defines “influenza-like illness”:

• Fever, meaning a temperature of 100°F (37.8°C) or greater, and
• Cough and/or sore throat, and
• No other known cause for the symptoms

It’s important to realize that these symptoms, on their own, are “non-specific,” meaning they can easily be caused by an illness other than influenza (such as a bad cold virus, strep throat, or even a bacterial pneumonia).

For this reason, health providers may decide to test a person for influenza, especially the test result might affect the decision to treat with anti-viral medication, or might help contain an outbreak.

“Uncomplicated” influenza is also often associated with other symptoms. The most common ones are nasal congestion and body aches.

Symptoms of influenza in older adults

Many older adults do develop typical symptoms when they fall ill from influenza.

But it’s also quite common for older adults to be sick from the flu and not have fever, cough, or sore throat.

Instead, older adults with the flu often experience the following problems due to influenza:

1. Common non-specific signs of illness in aging adults. These include symptoms such as:
   • Weakness
   • “Dizziness” (a term people often use when they are feeling weak or if they get light-headed when standing)
   • Loss of appetite
   • Confusion or worse-than-usual mental function (this is called delirium)
   • Malaise (which basically means feeling blah or unwell)
2. An exacerbation (meaning a worsening) of a chronic heart or lung condition. Examples include:
   • An exacerbation of chronic obstructive pulmonary disease, which often means increased shortness of breath, wheezing, and/or increased sputum production
   • An episode of worsening heart failure, which often means shortness of breath and/or increased leg swelling
   • A worsening of asthma symptoms

In a recently published study on influenza testing in older adults, during flu season, researchers independently tested all adults hospitalized with any type of respiratory diagnosis or shortness of breath for influenza.

They found that: “Among patients with study-confirmed influenza, ‘influenza-like illness’ was also less common in older patients (74% ≥ 65 years; 83% 50-64 years; and 81% 18-49 years).”

In other words, in this real-world study, 26% of hospitalized older adults with proven influenza did not have the typical “influenza-like illness” symptoms of fever plus cough or sore throat.

Why older adults may not show typical influenza symptoms

Here’s a core concept in geriatrics: as people age, they become less likely to have “typical” symptoms when they develop infections and some other types of illnesses.

This is due to two common issues that come up as people age: the aging of the immune system and decreased “physiologic reserve.”

Aging of the immune system

Aging is known to eventually bring on changes to the immune system. Since many common symptoms of illness actually reflect the immune system’s response to an infection, a less vigorous immune system will tend to generate less prominent symptoms.

For instance, fever is a very classic sign that the immune system is at work fighting infection. However, studies have found that older adults are less likely to have fever when they are ill with influenza.

Decreased “physiologic reserve”

The human body is designed to maintain stability and the ability to carry out key functions, even in the presence of stress or illness.  This is why even if one is sick, one can usually stand up, think straight, and key organs keep functioning adequately.

To maintain this stability, the body relies on an intricate system of detecting problems and working to correct them quickly. So for instance, if your blood pressure drops, your heart will speed up to help maintain adequate blood flow throughout the body.

The body’s organs are also usually designed to have “extra capacity,” meaning that they usually don’t have to work at their maximum ability, to do their job reasonably well.  So your brain usually doesn’t need to have all its neurons active and working well to do the thinking required, and your kidneys are able to keep your blood adequately filtered even if they lose some of their filtering ability.

At its peak resilience and effectiveness (usually when you’re in your mid-twenties), the body has lots of capacity to effectively respond to stressors.  All your organs have lots of capacity, and the body’s systems for coordinating and correcting things when there’s a problem work well.

This is called having a lot of “physiologic reserve.” So although it’s possible for a young person to become delirious — or unable to stand — due to illness, it usually takes a very severe illness to do this.

But alas, as we get older, most organs develop some wear or damage, due to aging or chronic diseases. So they don’t have quite as much extra capacity as they used to. And so all those systems for maintaining stability and function in the face of illness become less effective.

Different older adults of the exact same age can have different levels of physiologic reserve; it depends on the person and their state of health.

Still, the overall trend is the same for everyone: as we get older, our bodies and minds become less resilient. Hence when an illness makes us sick and stresses our body, some older adults will show signs of things going a bit “haywire,” rather than just showing the very typical symptoms caused by the illness or our immune response to the illness.

Many of those non-specific signs of illness in older adults — especially weakness and delirium — are caused by having decreased physiologic reserve. Developing a worsening of heart or lung problems also reflects decreased reserve. They are basically signs of the body starting to malfunction because an illness stressor has come up and the body’s systems for maintaining overall function and stability can’t quite keep up.

What we know about older adults & influenza testing

It’s not exactly news or a recent scientific breakthrough, that older adults often exhibit vague symptoms when ill with influenza. And just about every clinician knows that most of the hospitalizations and deaths related to influenza occur in older adults.

Despite this, research has found that clinicians sometimes fail to order influenza testing for sick older adults.

Here is the conclusion of the study published in January 2018 that I have been referencing:

“Adults 65 years and older hospitalized with fever or respiratory symptoms during influenza season are less likely to have a provider-ordered influenza test than younger adults.

Some, but not all, of this disparity is due to a lower likelihood of influenza-like illness presentation.”

What the CDC currently recommends, regarding influenza diagnosis and treatment

Since we’re in the midst of a particularly bad flu year, this past December the CDC issued a special health advisory on the diagnosis and treatment of influenza. (You can read it here.)

Tellingly, the advisory notes that it’s being issued for the following reasons:

• To “remind clinicians that influenza should be high on their list of possible diagnoses for ill patients because influenza activity is increasing nationwide.”
• To “advise clinicians that all hospitalized patients and all high-risk patients (either hospitalized or outpatient) with suspected influenza should be treated as soon as possible with a neuraminidase inhibitor antiviral.” (Emphasis mine.)

Here are some other important points made in the advisory:

• “Evidence from previous influenza seasons suggests that antivirals are underutilized in outpatients and hospitalized patients with influenza who are recommended for treatment.”
  • In other words, in the past doctors have often failed to offer antiviral influenza treatment to patients who should’ve gotten it, per the CDC’s recommendations.
• “All hospitalized, severely ill, and high-risk patients with suspected or confirmed influenza should be treated with antivirals.”
  • The CDC notes that high-risk individuals who aren’t hospitalized should be offered treatment.
  • Adults aged 65 and older are listed as “high-risk,” as are people with chronic pulmonary, cardiovascular, or kidney disease.
• “Antiviral treatment should be started as soon as possible after illness onset and should not be delayed even for a few hours to wait for the results of testing.”
  • The CDC notes that “clinical benefit is greatest when antiviral treatment is administered as early as possible after illness onset.”
  • Treatment should be started within 48 hours of illness onset. However, the CDC notes that starting treatment after 48 hours may still be beneficial for some people.
• “A history of current season influenza vaccination does not exclude a diagnosis of influenza.”
  • The CDC estimates that this year’s seasonal flu vaccine is probably 30% effective against the particular strain of influenza A (H3N2) which seems to be causing most of the severe illness. So a person who has been vaccinated can still become quite sick from the flu.
• “During influenza season especially, high-risk patients should be advised to call their provider promptly if they have symptoms of influenza.”
  • The CDC notes that providers may want to provide special phone lines to enable high-risk patients to discuss their symptoms by phone, and says that providers may want to consider providing a prescription for antivirals prior to an office visit.

The CDC advisory also includes a section on different types of influenza tests, and the CDC has a detailed page for clinicians here.

Now about those influenza tests. Probably the most important thing you should know about influenza tests is that they are not created equal, and some of them are known to have a significant “false negative” rate.

Meaning, certain influenza tests are known to have a non-negligible chance of missing people who actually are infected with influenza. (A test can also be falsely negative if the nasal swab is incorrectly done.)

The more accurate influenza tests are “molecular assays,” which test for the actual presence of viral proteins in a person’s nasal secretions.

However, it’s fairly common for healthcare providers to use an older (and cheaper) “rapid influenza diagnostic test (RIDT),” which provides a quick answer but is less accurate, and has a higher false negative rate.

Since the CDC is aware that some commonly used tests can miss influenza, the recent influenza advisory states: “Clinicians should be aware that a negative RIDT result does not exclude a diagnosis of influenza in a patient with suspected influenza when there is influenza activity in the community.”

What to do, if an older person falls ill during influenza season

I have shared a lot of information so far, so let me now try to boil it down to a few key take-aways. I will then share my top suggestions on what to do, for older adults who fall ill during flu season.

Key take-aways:

• When the flu is widespread, clinicians and families should be quick to suspect that a sick older person might have the flu, even if he or she doesn’t have a fever, a cough, a sore throat, body aches, or any of the other “typical” flu symptoms.
• In an older person, feeling weak or confused may be the only sign of having the flu.
• Influenza can become a life-threatening illness in older adults and other high-risk groups of people. Prompt recognition of possible influenza and prompt treatment with anti-influenza medication is key to reducing the chance of serious illness and death.
• Anti-influenza medications are most effective when started as soon as possible after the onset of illness, and preferably within 48 hours.
  • Per the CDC, treatment should not be delayed while waiting for the result of an influenza test.
  • The CDC also notes that the “rapid influenza diagnostic test” is not always accurate, and should not be used to rule out the flu if there has been a lot of influenza activity in the area.
• Research suggests that some health care providers may fail to recognize or test for influenza in older adults.

My recommendations on what to do:

• When the flu is widespread, be quick to suspect that a sick older person might have the flu.
  • Remember that older adults can get quite sick from the flu even if they don’t have a fever, a cough, a sore throat, body aches, or any of the other “typical” flu symptoms.
  • A worsening of a chronic heart or lung condition (especially COPD or heart failure) can be caused by influenza.
• Don’t delay in seeking medical attention, and in asking about anti-virals for influenza.
• Be proactive about asking for influenza testing and anti-virals while any test results are pending.
  • Don’t expect the doctors to check for influenza or offer anti-virals. Many will, but some won’t.
• If a rapid influenza test is negative in an older person who is quite sick or has typical flu symptoms, ask about getting a more accurate test done.

Hopefully, the doctors will appreciate your proactive approach and how well-informed you are.

But I’ll be honest with you: you may have to be persistent, especially if the doctor waves off your concern or questions about influenza. (Or worse yet, if they say something like “What medical school did YOU go to?” when you ask extra questions.)

It’s not right that patients and families get pushback, especially when they are asking for care that is in line with guidance from the CDC or another relevant expert group. But it does happen 🙁

I hope this won’t happen to you, but if you think it might, then consider bringing in a copy of the CDC’s recent advisory. And remember, it’s always best to be as polite and appreciative as possible, when persisting and asking health providers to do a little more.

With the help of informed and proactive families, we can help more older adults get the care they need, and so reduce serious illnesses and deaths from the flu.

Questions? Comments? Post them below!

[Many thanks to Bob Barnett of Bottom Line Health, Inc., for alerting me to the recently published article on influenza testing in hospitalized adults.]