There are more than 30 different causes of pneumonia, including bacteria, viruses, airborne irritants, and fungi. When these germs enter the lungs, they can overpower the immune system and invade nearby lung tissues, which are very delicate.
Once infected, the air sacs in the lungs become inflamed and fill up with fluid and pus, which causes coughing, fever, chills, and breathing problems.
Is Pneumonia Contagious?
You don’t catch pneumonia, in fact — you catch the germs that cause it.
You can encounter the germs that cause pneumonia in the most common of places, and the environment you frequent on a daily basis may contribute to how susceptible you are to the disease.
For example, children in school or day care facilities can easily catch viruses from one another, which makes them more prone to viral pneumonia.
In general, viral pneumonia is more likely to spread from person to person than pneumonia caused by a bacteria or fungus.
Some types of pneumonia spread only in certain environments.
For example, Legionnaires’ disease, which is caused by the bacteria Legionella pneumophila, may only pose a threat to people exposed to a contaminated air conditioning system. It has also been linked to inhaling droplets from whirlpools, spas, or fountains.
If you catch germs that cause pneumonia, your chance of developing the disease depends on your age, health, and lifestyle.
What Is Bacterial Pneumonia?
Bacteria are the most common cause of pneumonia in adults.
Bacterial pneumonia may follow a viral infection, like a cold or the flu (influenza). This type of pneumonia usually affects one area of the lung and is referred to as lobar pneumonia.
Types of bacteria that cause pneumonia include:
- Streptococcus pneumoniae
- Legionella pneumophila, the cause of Legionnaires’ disease, or Legionellosis
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Haemophilus influenzae type B (Hib)
Streptococcus pneumoniae, also known as pneumococcus, is the most common cause of bacterial pneumonia in adults, called pneumococcal pneumonia.
It may be prevented by a vaccine. The Centers for Disease Control and Prevention (CDC) recommends two pneumonia vaccines for adults 65 years and older: pneumococcal conjugate vaccine, or Prevnar 13 (PCV13), and pneumococcal polysaccharide vaccine, or Pneumovax 23 (PPSV23).
According to the CDC:
- You should receive a dose of the pneumococcal conjugate vaccine (PCV13) first, followed at least one year later by a dose of the pneumococcal polysaccharide vaccine (PPSV23).
- If you’ve already received any doses of PPSV23, the dose of PCV13 should be given at least one year after the most recent PPSV23 dose.
- If you’ve already received a dose of the PCV13 at a younger age, another dose is not recommended.
Mycoplasma pneumoniae usually infects younger adults who work in crowded areas, such as schools, homeless shelters, or prisons.
Chlamydophila pneumoniae causes a mild pneumonia infection that usually affects people older than 60.5
Haemophilus influenzae type B (Hib) infection can be prevented with a vaccine, called the Hib vaccine. It’s recommended for all children younger than age 5 and is usually given to infants starting at 2 months old.
Most bacteria that cause pneumonia are pyogenic bacteria, which means that they form pus, a combination of debris from serum, dead bacteria, and white blood cells. A cough that produces discolored mucus in the presence of fever and shortness of breath can be a classic sign of bacterial pneumonia.
Other bacterial pneumonia symptoms include:
- High fever
- Chills
- Rapid breathing
- Pain when coughing or breathing deeply
- Shortness of breath
- Exhaustion
- Loss of appetite
Bacterial pneumonias tend to be more serious with more noticeable symptoms than other types of pneumonia.
What Is Walking Pneumonia?
A mild case of bacterial pneumonia, often called walking pneumonia, features symptoms similar to the common cold, including:
- Persistent dry cough that often gets worse at night
- Low-grade fever
- Shortness of breath
- Fatigue or tiredness
- Chest pain that gets worse when you take a deep breath or cough
- Loss of appetite
Some less-common symptoms of walking pneumonia may also include:
- Diarrhea
- Rash
- Sore throat
What Is Viral Pneumonia?
Viruses are responsible for about one-third of all pneumonias, and they’re the most common cause of pneumonia in children younger than age 5
Viral pneumonias tend to clear up in about one to three weeks, but they can increase your risk for bacterial pneumonia.
Viral pneumonia is usually less serious than bacterial pneumonia.
At first, the symptoms of viral pneumonia may be similar to symptoms often associated with the flu, except you may experience a dry cough that does not produce phlegm. You may also develop a fever and headache.
But within a couple of days, these symptoms typically get worse.
Adults with viral pneumonia can also expect to develop:
- Sore throat
- Loss of appetite
- Muscle pain
The flu virus is the most common cause of viral pneumonia in adults, which tends to be more serious in people with heart or lung disease, senior citizens, and pregnant women.
Not only can influenza cause pneumonia, it can also predispose people to bacterial pneumonia — yet another good reason to get the yearly flu shot.
Respiratory syncytial virus (RSV) pneumonia is usually a mild infection that clears up in about a week or two. It can be more severe and is more common in young children and older adults. In fact, RSV is the most common cause of pneumonia in children younger than 12 months.
What Is SARS?
Severe acute respiratory syndrome (SARS) is a type of pneumonia triggered by the type of viruses that cause the common cold — and it spreads like a cold.
This virus was first identified in 2003, when there were about 8,000 cases reported worldwide. Since then, cases have become less common, but this form of viral pneumonia can be deadly in elderly people.
What Is Fungal Pneumonia?
Three types of fungi living in soil are known causes of pneumonia:
- Coccidioides immitis and Coccidiodes posadasii are two related fungi common to the American Southwest. Both can cause coccidioidomycosis, also known as cocci or valley fever.
- Histoplasma capsulatum is found in the central and eastern United States, especially areas around the Ohio and Mississippi River valleys, and causes a disease called histoplasmosis.
- Cryptococcus is a fungi found in soil and bird droppings all across the country.
Most people who inhale these fungi don’t get sick, but if your immune system is weak, you may develop pneumonia.
Another fungus, Pneumocystis jirovecii, can generate an infection in premature, malnourished infants, and in people with a weakened immune system, such as those who have HIV or AIDS.
The symptoms of pneumonia that are caused by fungi are often similar to those of other forms of pneumonia, including a fever, dry cough, shortness of breath, and fatigue.
But because this type of pneumonia usually affects people with weakened immune systems, symptoms tend to develop faster, and people often experience a high fever.
What Health Complications Can Pneumonia Lead To?
If you have flu-like symptoms that persist or worsen despite treatment, talk to your doctor.
Your doctor can monitor your lungs while you inhale, listening for crackling sounds that are audible only with a stethoscope.
In order to confirm the diagnosis and identify the specific germ causing the illness, you may get a chest X-ray as well as a blood test, depending on your medical history and physical exam, if your doctor suspects that you have pneumonia.
If left untreated, pneumonia can become severe.
People with severe pneumonia experience higher fevers along with GI symptoms, such as vomiting and diarrhea, as well as:
- Difficulty breathing
- Excessive sweating
- Rapid breathing
- Rapid heart rate
- Bluish tint to lips and nails from a lack of oxygen in the blood
If you have trouble breathing, don’t wait for an office visit with your doctor; go to the emergency room right away.
Older people may also become confused or less aware of what’s going on around them if they develop pneumonia. Rather than a fever, their temperatures might be lower than normal, and they may have milder or fewer symptoms. Even so, a serious infection may still be brewing that requires medical attention.