DEAR DR. ROACH: My son-in-law had Guillain-Barre as a child, and is now 39 and a new father. He has an executive job with nothing strenuous. He cannot get the flu shot and consequently got the flu. He has been diagnosed with an infection around the heart and was hospitalized for several days.

No one seems able to cure this. Recently he was told he may never return to work and cannot do any heavy lifting or exercising, including taking care of the baby. My concern is about what is going to happen to his quality of life — attention to his wife, who wants more children; his job; and day-to-day functioning, like just taking out the garbage. Why are the doctors telling a 39-year-old man that sitting on the sofa for the rest of his life is the outcome? Maybe I am unsympathetic here, but is there truth to this? — A.R.

ANSWER: My suspicion is that your son-in-law has suffered a serious complication of a viral infection: viral myocarditis. It is a rare complication of several viral infections, including influenza, but also other viruses, such as Coxsackie B and even the coronavirus. The virus and the body’s response to it both can damage the heart muscle. Based on your reports, I suspect your son-in-law has developed heart failure due to an infection.

With heart failure, the heart is unable to pump the blood the body needs (called systolic function) and maintain low pressures to keep the lungs healthy (diastolic function). Heart failure causes fatigue and low energy, as well as shortness of breath, especially with exertion. The feet (or other body areas) may swell with fluid. Symptoms can range in severity from barely noticeable to bad enough to limit activities of daily life.

Since this apparently was only diagnosed in a short period of time, it’s important to note that the prognosis is highly variable. Most people will recover a great deal or all of their function. But if my suspicion that your son-in-law had viral myocarditis is correct, it is possible that his course may be much longer.

Even severe cases may be successfully treated, however. There are many effective medications, and in the most serious cases, things like mechanical aids to heart function and transplant can be considered. That kind of severe heart failure should be managed by an expert, ideally a cardiologist with special expertise in heart failure.

The diagnosis of viral myocarditis is difficult to make with certainty. The most definitive test is a biopsy, done via cardiac catheterization. Those who need a biopsy are likely to be the sickest of those with viral myocarditis.

It can be very hard to accept that a healthy person can change to a person in severe medical distress in a short time. Your expectations may have to change. While there is an excellent chance for full recovery, those with biopsy-proven myocarditis have about a 50% mortality at five years.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.