Can the Flu Turn Into Pneumonia?
Key takeaways:
The flu is a viral respiratory illness that usually resolves on its own. But it’s possible to develop complications from the flu, like pneumonia.
The most common cause of viral pneumonia is the flu virus.
One of the effects of the flu virus is that it weakens the immune system. This can make it tougher to fight off other infections.
The flu is a common respiratory infection that most people will have at some point in their lifetime. Many recover from the flu in about a week. But some people go on to have serious complications — like pneumonia.
Pneumonia is an infection where part of one or both lungs fill with pus or fluid. This can happen as your immune system tries to fight off an infection. The flu doesn’t always turn into pneumonia. But there are some risk factors that can make it more likely.
Let’s take a closer look at the signs you may be developing pneumonia and when to seek help.
Search and compare options
What are the differences between the flu and pneumonia?
The flu and pneumonia are both respiratory illnesses that can cause cough and affect your breathing. But they’re different conditions with different causes. They also have different symptoms and treatments.
Let’s take a closer look at the flu and pneumonia, as well as their differences.
Flu | Pneumonia | |
What causes it? | • Influenza virus | • Can be caused by a virus, bacteria, or fungi |
What are the symptoms? | • Fever • Chills • Cough • Sore throat • Muscle aches • Fatigue • Headache | • Fever • Cough with mucus • Shortness of breath • Chest pain • Fatigue • Bluish color to lips or nails • Decreased appetite |
When do symptoms appear? | • Usually come on suddenly | • Can sometimes develop slowly over several days |
How long does it last? | • Usually resolves in 1 to 2 weeks | • Varies from person to person; can last for days or several weeks after treatment begins |
How do you treat it? | • Most often resolves on its own • Antivirals can be used in high-risk cases | • Depends on the cause, but antibiotics, antivirals, and antifungals can be used |
Can the flu turn into pneumonia?
The short answer is yes. The flu can result in pneumonia in two different ways: direct infection (viral pneumonia) and secondary infection.
The influenza virus can directly infect the cells in the lungs. In fact, the flu is the most common cause of pneumonia in adults. Flu and pneumonia are a dangerous combination. Together, they’re a leading cause of death in the U.S. every year.
In addition to directly causing pneumonia, the influenza virus can weaken the immune system. A weak immune system isn’t able to fight off bacteria that make their way into the lungs. If the bacteria aren’t cleared by the immune system, they can flourish and cause a lung infection, in addition to the flu. The flu can turn into a “secondary bacterial infection” of the lungs (secondary pneumonia).
Can you have pneumonia and the flu at the same time?
Yes, it’s possible to have pneumonia and the flu at the same time. Pneumonia can be caused by a variety of germs. So, it’s possible to be infected with the flu and another germ that causes pneumonia — like COVID-19 — together.
This may be more likely to happen when the immune system isn't strong, causing more than one virus or bacteria to invade. That's why it’s a good idea to seek medical attention when you have symptoms of the flu or pneumonia. A healthcare professional can run some tests to see exactly what infection(s) are causing your symptoms.
Is that nagging cough something to worry about? Here’s when you need to see a healthcare professional for your cough.
Your cough will likely go away on its own. Learn more about when you might need antibiotics to treat it.
Can you get pneumonia with COVID-19? Yes, and here’s why.
What makes it more likely to get pneumonia after the flu?
Most of the time, the flu doesn't turn into pneumonia. But certain risk factors can make it more likely, such as:
Age: Children ages 2 and younger and adults older than age 65 are at higher risk of getting pneumonia from the flu.
Chronic conditions: Your risk is increased if you have health problems such as asthma, chronic obstructive pulmonary disease (COPD), diabetes, and heart disease.
Smoking: Smoking can harm the lungs and make it easier to get pneumonia after having the flu.
Severe flu infection: If you end up in the hospital because of the flu, your risk of getting pneumonia goes up.
How can you prevent the flu from turning into pneumonia?
Taking care of your health can lower the chance of getting sick and keep you healthier during flu season. Here are a few simple steps that can make a big difference in preventing flu complications, like pneumonia:
Get vaccinated. The flu shot lowers the risk of getting the flu. It also reduces the chances of complications, including pneumonia.
Practice good hygiene. Regularly wash your hands with soap and water, especially after coughing or sneezing. Using hand sanitizer is also helpful in killing germs.
Avoid close contact. Try to avoid close contact with people who are sick. If you're not feeling well, keep your distance as well to stop the spread of flu.
Stay healthy. Eat nutritious food, exercise, and make sure to get enough sleep. A strong immune system can fight off infections better.
Avoid smoking. If you do smoke, quitting is beneficial for your overall lung health. This can help prevent health problems.
Get care early. Within 2 days of flu symptoms, antiviral medicines like Tamiflu are sometimes helpful. They can reduce how bad the flu gets and lower your risk of complications.
How can you tell if the flu is turning into pneumonia?
If you have the flu and start to feel worse rather than better over the next 7 to 10 days, you might be developing a complication like pneumonia. Some signs include:
More trouble breathing
Chest congestion
Fever that won't go away
If you start to have these symptoms, you’ll need to make an appointment for medical attention right away. A healthcare professional may order an X-ray or blood tests to see if pneumonia is causing your symptoms.
When should you see a healthcare professional for flu symptoms?
Most people can recover from the flu at home. But sometimes you need to get medical attention for your flu symptoms. This is especially important for young kids, older people, or those with underlying medical conditions who are at risk of serious complications.
Signs you need to see a healthcare professional are:
Symptoms that aren’t improving or are getting worse
Fever that doesn't get better
Trouble breathing
Cough that won't go away
Chest pain
Lack of appetite
Frequently asked questions
Most of the time, you can visit your primary care provider to get a flu test and prescriptions for flu medications. Sometimes, flu symptoms can be life-threatening and require a hospital or emergency department visit. Some of the main reasons to go to the hospital with the flu are:
Chest or abdominal pain
Shortness of breath
Dizziness, fainting, or bluish color to the skin
Worsening of chronic medical conditions
Seizures
Persistent vomiting or vomiting/coughing up blood
Stiff neck
If you’re unsure, call a healthcare professional or 911.
It can be hard to diagnose pneumonia yourself. If you have the flu or another viral infection, the symptoms may be similar to pneumonia. Symptoms to look out for include:
Cough with phlegm or mucus
Fever and chills
Achy chest or pain with breathing
Shortness of breath
Symptoms not improving or getting worse after a few days
If you have these symptoms, you should see a healthcare professional. They’ll listen to your chest, and they may order blood tests or an X-ray.
In the first stage of pneumonia, there’s primarily congestion. The lung tissue is filled with fluid and germs, but few red cells or immune cells (neutrophils). You may only have a wet cough at this stage, without more severe symptoms.
The bottom line
The flu is a common respiratory illness that can sometimes lead to serious problems, like pneumonia. The flu virus itself can cause pneumonia. And sometimes it can make you more vulnerable to getting other germs that cause pneumonia. It’s also possible to have infections with both the flu and pneumonia at the same time. Young children, older adults, and people with chronic medical conditions are more likely to develop pneumonia from the flu.
If you have worsening flu symptoms, it’s best to get medical help right away. A healthcare professional can figure out if your symptoms are due to a complication like pneumonia.
Why trust our experts?
References
Arcavi, L., et al. (2004). Cigarette smoking and infection. Archives of Internal Medicine.
Ballinger, M. N., et al. (2010). Postinfluenza bacterial pneumonia: Host defenses gone awry. Journal of Interferon & Cytokine Research.
Bartley, P. S., et al. (2022). Bacterial coinfection in influenza pneumonia: Rates, pathogens, and outcomes. Infection Control and Hospital Epidemiology.
Canadian Paediatric Society Infectious Diseases and Immunization Committee. (2005). Influenza in children. Paediatrics & Child Health.
Centers for Disease Control and Prevention. (2018). Flu vaccine among adults with current asthma.
Centers for Disease Control and Prevention. (2024). Flu and people with diabetes.
Centers for Disease Control and Prevention. (2024). Healthy habits to prevent flu.
Centers for Disease Control and Prevention. (2024). Influenza.
Centers for Disease Control and Prevention. (2024). Treating flu with antiviral drugs.
Chu, S., et al. (2017). Incidence and risk factors of pneumonia in hospitalized patients with seasonal influenza A or B. Tuberculosis and Respiratory Diseases.
EmergencyPhysicians.org. (n.d.). Flu. American College of Emergency Physicians.
Jain, V., et al. (2023). Pneumonia pathology. StatPearls.
Liao, K., et al. (2022). The influence of influenza virus infections in patients with chronic obstructive pulmonary disease. International Journal of Chronic Obstructive Pulmonary Disease.
MedlinePlus. (2023). Pneumonia.
National Heart, Lung, and Blood Institute. (2022). Pneumonia: Causes and risk factors.
National Heart, Lung, and Blood Institute. (2022). What is pneumonia?
National Institute on Aging. (2022). Flu and older adults.
