This condition, when treated promptly, typically lasts about two weeks (though it can last even longer in young children, the elderly and those who have compromised immune systems). For those in high-risk categories, you can ask your doctor about the pneumococcal vaccines -- for children or adults -- that provide immunity against the 23 types of bacteria that commonly cause pneumonia.
Myocarditis
This complication is far rarer than pneumonia but can result from the flu in otherwise healthy children and adults and is characterized by the inflammation or destruction of the myocardium (middle layer of the heart wall) and can lead to rapid heart failure or blood clot formation resulting in a stroke or heart attack.
Patients who develop myocarditis typically experience difficulty breathing, edema (fluid buildup) around the ankles or calves, sharp, shooting pain when breathing, and irregular heart rhythms. Prompt medical attention can result in treatment including antivirals (if a virus caused the condition) as well as steroids. Prompt medical attention is imperative -- for some, a full recovery is possible, while others will be forced to be on cardiac medications for life or even require a heart transplant.
Guillain-Barre Syndrome
This complication only strikes one or two cases per 100,000 people each year, developing as a result of a cold or flu (or a number of other illnesses). This autoimmune disorder progressively affects muscle strength. Patients typically develop varying degrees of weakness or tingling in the legs, which spreads to the arms and upper body. These symptoms increase in severity until some muscles cannot be used at all. In severe cases - which are life-threatening, a person may be almost totally paralyzed, with the condition affecting the ability to breathe. In these cases, patients are placed on ventilators.
Diagnosis of this condition can be a challenge because it involves ruling out other causes of weakness that are more common. While there is no cure, treatment for this condition includes supportive care, antibody treatments and plasma exchange. While recovery is possible, it is typically a slow process, with about two-thirds of patients taking a month or more to see an improvement in their condition.