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Getting the flu is no fun, but what’s even worse than the runny nose, cough, fever, and other symptoms related to the flu, is when complications arise. Pneumonia is one of the most common complications that can occur as a result of the flu. The condition can become very serious and even life-threatening.

Once the immune system is compromised, or while it is fighting a virus, patients have a higher risk of developing more severe infections, such as pneumonia. Children, those over age 65, those who are pregnant, those who have chronic medical conditions, or those who have a weakened immune system may have an increased risk of complications.  According to the World Health Organization (WHO), pneumonia accounts for 14% of all deaths of children under 5 years old, killing 740 180 children in 2019.

Normally, flu symptoms can be treated at home and people don’t always need to see a doctor; however, being aware of symptoms can help determine whether a case of the flu has become more serious. Certain serious flu-like symptoms are crucial to watch for, such as serious congestion or chest pain, difficulty breathing, a fever over 102 degrees, or coughing that produces pus. Any one of those symptoms warrants a visit to a doctor. In general, if symptoms persist for more than 3-5 days, it’s always better to be cautious and see a healthcare provider.


Diagnosing Flu and Pneumonia

Healthcare providers can leverage rapid diagnostic tests to help determine whether patients have a case of the flu. Test results can be vital in determining the best treatment option for managing symptoms. The most common tests used to detect flu viruses in respiratory specimens are called rapid influenza diagnostic tests, or RIDTs. Another type of test that may also be used is a rapid molecular assay, which is often more accurate than RIDTs. Both tests produce results in a range of 10-20 minutes to help guide decision making. The most accurate tests, however, must be performed in specialized laboratories and include reverse transcription polymerase chain reaction (RT-PCR), viral culture, and immunofluorescence assays. Results from those tests may take one to several hours.

The flu is caused by viruses and not bacteria, so antibiotics will not help fight the infection. Because of that, determining whether you have the flu based on diagnostic test results can aid antimicrobial stewardship efforts that support the judicious use of antibiotics. However, if a patient develops pneumonia as a secondary complication to the flu, then antibiotics may be necessary, depending on the pathogen that is causing the pneumonia.

Pneumonia is an infection of the lungs, and can be caused by bacteria, viruses, and fungi. It can range from mild to severe and symptoms may include a high fever, a cough that doesn’t improve, shortness of breath with daily activities, or feeling worse after the flu. Specifically, the infection causes the lungs to become inflamed and fill up with fluid, making it difficult for oxygen to get into the bloodstream.

Diagnostic tests and imaging can play a vital role in delivering an accurate and swift diagnosis for pneumonia. Due to the seriousness of pneumonia, it is important that treatment is initiated quickly once the diagnosis is confirmed. A provider may initiate one of the following tests to help confirm the diagnosis: chest x-ray to detect the presence of inflammation in the lungs, blood test (such as complete blood count or CBC to see whether the immune system is fighting an infection), or pulse oximetry to measure how much oxygen is in the blood. While those tests can help determine the presence of pneumonia, they cannot identify the underlying cause.

Doctor examining lungs x-ray scan in his office in hospital close up

Additional testing is necessary to identify the causative pathogen (or pathogens). In general, bacteria are the most frequent cause of pneumonia; however, about one third of pneumonia cases are viral. Fungi can also cause pneumonia, although it is not as common. Blood culture, sputum culture, pleural fluid culture, and polymerase chain reaction (PCR) testing may be used to help identify the pathogen. These tests can help healthcare providers tailor treatment appropriately.


Preventing Flu and Pneumonia 

Many factors determine how serious pneumonia may be, including its cause as well as the patient’s age and overall health. Getting the annual flu vaccine is of the best ways to prevent flu related complications such as pneumonia. Even for patients who get the flu after being vaccinated, symptoms are often less serious, and recovery is frequently faster.


This information is for general educational purposes only and is not intended to be a substitute for professional medical advice. Always consult a medical director, physician, or other qualified health provider regarding diagnosis and treatment of a medical condition.




  • Infectious Diseases