Pneumonia symptoms

Pneumonia – Symptoms and Causes


Pneumonia is an infection that inflames the air sacs in one or both lungs. The alveoli may fill with fluid or pus (purulent matter), causing a cough with phlegm or pus, fever, chills and difficulty breathing. A variety of organisms, including bacteria, viruses, and fungi, can cause pneumonia.

Pneumonia can range in severity from mild to life-threatening. It is more serious for infants and young children, people over 65, and people with medical conditions or weakened immune systems.



Signs and symptoms of pneumonia range from mild to severe, depending on factors such as the type of germ causing the infection, your age, and your general health. Mild signs and symptoms often resemble those of a cold or flu, but last longer.

Signs and symptoms of pneumonia can include:

  • Chest pain when breathing or coughing
  • Confusion or changes in mental awareness (in adults 65 years and older)
  • Cough, which may produce phlegm
  • Fatigue
  • Fever, sweating and chills
  • Lower than normal body temperature (in adults over 65 and people with weakened immune systems)
  • Nausea, vomiting or diarrhea
  • Shortness of breath

Newborns and infants may show no signs of infection. Or they may vomit, have a fever and cough, appear restless or tired and listless, or have difficulty breathing and eating.

When to consult a doctor

See your doctor if you have difficulty breathing, chest pain, a persistent fever of 102 F (39 C) or higher, or a persistent cough, especially if you cough up pus.

It is especially important for people in these high-risk groups to see a doctor:

  • Adults over 65
  • Children under 2 with signs and symptoms
  • People with an underlying health condition or weakened immune system
  • People receiving chemotherapy or taking drugs that suppress the immune system

For some older adults and people with heart failure or chronic lung problems, pneumonia can quickly become a life-threatening illness.

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Many germs can cause pneumonia. The most common are bacteria and viruses in the air we breathe. Your body usually prevents these germs from infecting your lungs. But sometimes these germs can overpower your immune system, even if your health is generally good.

Pneumonia is categorized by the types of germs that cause it and where you got the infection.

Community-acquired pneumonia

Community-acquired pneumonia is the most common type of pneumonia. It occurs outside of hospitals or other health care facilities. This can be caused by:

  • Bacteria. The most common cause of bacterial pneumonia in the United States is Streptococcus pneumoniae. This type of pneumonia can occur on its own or after a cold or the flu. It can affect part (lobe) of the lung, a condition called lobar pneumonia.
  • Bacteria-like organisms. Mycoplasma pneumoniae can also cause pneumonia. It generally produces milder symptoms than other types of pneumonia. Walking pneumonia is an informal name given to this type of pneumonia, which is usually not severe enough to require bed rest.
  • Mushrooms. This type of pneumonia is more common in people with chronic health conditions or weakened immune systems, and in people who have inhaled high doses of the organisms. The fungi that cause it can be found in soil or bird droppings and vary by geographic location.
  • Viruses, including COVID-19[feminine]. Some of the viruses that cause colds and flu can cause pneumonia. Viruses are the most common cause of pneumonia in children under 5 years old. Viral pneumonia is usually mild. But in some cases, it can become very serious. Coronavirus 2019 (COVID-19) can cause pneumonia, which can become serious.

Nosocomial pneumonia

Some people get pneumonia while in hospital for another illness. Nosocomial pneumonia can be serious because the bacteria that causes it may be more resistant to antibiotics and because people who have it are already sick. People who use breathing machines (ventilators), often used in intensive care units, are at higher risk for this type of pneumonia.

Nosocomial pneumonia

Nosocomial pneumonia is a bacterial infection that occurs in people who live in long-term care facilities or receive care in outpatient clinics, including kidney dialysis centers. Like hospital-acquired pneumonia, hospital-acquired pneumonia can be caused by bacteria that are more resistant to antibiotics.

Aspiration pneumonia

Aspiration pneumonia occurs when you inhale food, drink, vomit, or saliva into your lungs. Aspiration is more likely if something disrupts your normal gag reflex, such as a brain injury or problem swallowing, or excessive alcohol or drug use.

Risk factors

Pneumonia can affect anyone. But the two age groups most at risk are:

  • Children 2 years or younger
  • People aged 65 or over

Other risk factors include:

  • To be hospitalized. You are at higher risk of pneumonia if you are in a hospital intensive care unit, especially if you are on a machine that helps you breathe (a ventilator).
  • Chronic disease. You are more likely to get pneumonia if you have asthma, chronic obstructive pulmonary disease (COPD) or heart disease.
  • Smoking. Smoking damages your body’s natural defenses against bacteria and viruses that cause pneumonia.
  • Weakened or suppressed immune system. The people who have HIV/AIDSwho have had an organ transplant or are receiving long-term chemotherapy or steroids are at risk.


Even with treatment, some people with pneumonia, especially those in high-risk groups, may experience complications, including:

  • Bacteria in the blood (bacteremia). Bacteria that enter the bloodstream from your lungs can spread the infection to other organs, potentially causing organ failure.
  • Difficulty breathing. If your pneumonia is severe or you have chronic underlying lung conditions, you may have difficulty getting enough oxygen. You may need to be hospitalized and use a breathing machine (ventilator) while your lung heals.
  • Accumulation of fluid around the lungs (pleural effusion). Pneumonia can cause fluid to build up in the thin space between the layers of tissue that line the lungs and the chest cavity (pleura). If the fluid becomes infected, you may need to have it drained through a chest tube or surgically removed.
  • Pulmonary abscess. An abscess occurs if pus forms in a lung cavity. An abscess is usually treated with antibiotics. Sometimes surgery or drainage with a long needle or tube placed in the abscess is needed to remove the pus.


To help prevent pneumonia:

  • To get vaccinated. Vaccines are available to prevent certain types of pneumonia and the flu. Talk to your doctor about getting these injections. Vaccination guidelines have changed over time, so be sure to review your vaccination status with your doctor even if you remember ever having received a pneumonia shot.
  • Make sure children are vaccinated. Doctors recommend a different pneumonia vaccine for children younger than 2 years old and for children 2 to 5 years old who are at particular risk of pneumococcal disease. Children attending community day care should also be vaccinated. Doctors also recommend the flu shot for children over 6 months old.
  • Practice good hygiene. To protect yourself from respiratory infections that sometimes lead to pneumonia, wash your hands regularly or use an alcohol-based hand sanitizer.
  • Do not smoke. Smoking damages your lungs’ natural defenses against respiratory infections.
  • Keep your immune system strong. Get enough sleep, exercise regularly and eat a healthy diet.