how do you get pneumonia

You get pneumonia when germs or foreign substances enter your lungs, overwhelm your immune system, and cause inflammation in the tiny air sacs (alveoli), which then fill with fluid or pus.¹²³

How Germs and Substances Enter Your Lungs

• Inhaling Respiratory Droplets: You can catch contagious bacteria and viruses when an infected person coughs, sneezes, or talks, and you breathe in those airborne droplets or touch a contaminated surface and then touch your face.¹²
• Secondary Viral Infections: Many cases of bacterial pneumonia start after you already have a viral illness like the flu, COVID-19, or a common cold. The initial virus weakens your respiratory defenses, making it easier for bacteria to take hold.¹²
• Aspiration: You can get aspiration pneumonia if you accidentally inhale food, drink, vomit, or saliva down your windpipe and into your lungs. This is more likely if a health condition, medication, or substance use disturbs your normal gag reflex.¹²³
• Inhaling Fungi: You can inhale fungal spores from contaminated soil or bird droppings. This type of pneumonia is rare in healthy individuals.¹²³

Main Causes of Pneumonia

• Bacteria: Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause. Other bacteria include Mycoplasma pneumoniae (often called walking pneumonia), Haemophilus influenzae, and Staphylococcus aureus.
• Viruses: Common culprits include influenza (the flu), respiratory syncytial virus (RSV), and SARS-CoV-2 (COVID-19).
• Fungi: Less common and typically affects people with weakened immune systems or chronic health issues.¹²³⁴⁵⁶

Who is at Higher Risk?

Certain factors make it easier to develop pneumonia:¹

• Age: Infants, young children, and adults over 65.
• Medical Conditions: Asthma, COPD, heart disease, diabetes, or a weakened immune system.
• Lifestyle Factors: Smoking damages lung tissue and makes infections more likely.¹²³

For detailed guidance on symptoms, risk reduction, and vaccination options, visit the NHS Pneumonia Guide or the Cleveland Clinic Pneumonia Overview.¹²

You get pneumonia when germs or foreign substances enter your lungs, causing the tiny air sacs (alveoli) to become inflamed and fill with fluid or pus. According to the NHS, it is most commonly triggered by a bacterial or viral infection.¹²³

Common Ways You Catch It

• Breathing in airborne droplets. When someone with a respiratory infection coughs, sneezes, or talks, tiny droplets containing bacteria or viruses enter the air. Inhaling these germs can allow them to travel deep into your lungs.¹²
• As a complication of another illness. Pneumonia frequently develops after you have had a common viral infection like the flu, a cold, COVID-19, or respiratory syncytial virus (RSV). Fighting off the initial virus temporarily weakens your immune system and irritates your airways, making it easier for bacteria to take hold.¹²³
• Touching contaminated surfaces. You can pick up pneumonia-causing germs by touching an object or surface with bacteria or viruses on it and then touching your nose or mouth.¹
• Inhaling food, liquid, or vomit. Known as aspiration pneumonia, this happens when foreign substances go down your windpipe into your lungs instead of your stomach. This is more common if your gag reflex is impaired by a swallowing problem, a brain injury, or heavy alcohol or drug use.¹²³
• Inhaling fungal spores. Fungal pneumonia is rare in healthy people in the UK. It usually affects people with weakened immune systems who breathe in large amounts of fungi found in soil or bird droppings.¹²³

Where It Is Contracted

Doctors often group pneumonia by where the infection was picked up, as this helps determine the best treatment:¹

• Community-acquired pneumonia. This is the most common form and happens in everyday settings like schools, workplaces, or public transport. The bacterium Streptococcus pneumoniae is the leading culprit.
• Hospital-acquired pneumonia. Patients can catch this during a hospital stay for another illness or surgery. It is often more serious because hospital bacteria can be resistant to standard antibiotics, and patients are already unwell. Those on breathing machines (ventilators) face the highest risk.¹²³⁴

Who Is Most at Risk?

While anyone can get pneumonia, NHS inform notes that certain groups are more vulnerable because their immune systems or lungs are less able to fight off germs:¹²

• Babies and very young children. Their immune systems are still developing.
• Adults over 65. Natural immunity weakens with age.
• People who smoke. Smoking damages the lungs' natural defences against infection.
• People with chronic conditions. Long-term illnesses like asthma, cystic fibrosis, diabetes, or heart, kidney, and liver disease increase vulnerability.
• People with weakened immune systems. This includes those undergoing chemotherapy, taking immunosuppressant drugs, or living with conditions like HIV.¹²³⁴

(Note: Being cold or wet does not directly cause pneumonia, though cold weather encourages people to gather indoors where viruses and bacteria spread more easily.) ¹²

Pneumonia is a lung infection that happens when germs cause inflammation in the tiny air sacs (alveoli) in your lungs. These air sacs can fill with fluid or pus, making it harder to breathe.

How do you get pneumonia?

You can develop pneumonia in several ways:

1. Bacterial infection – Often caused by bacteria such as Streptococcus pneumoniae.
2. Viral infection – Viruses such as flu, COVID-19 and RSV can lead to pneumonia.
3. Fungal infection – Less common, usually affecting people with weakened immune systems.
4. Aspiration – Accidentally breathing food, drink, saliva or vomit into your lungs can cause aspiration pneumonia.

Is pneumonia contagious?

Pneumonia itself isn't always contagious, but the viruses and bacteria that cause some types can spread between people through:

• Coughing and sneezing.
• Close contact with someone who is infected.
• Touching contaminated surfaces and then touching your face.

What are the symptoms?

Common symptoms include:

• Persistent cough (sometimes producing yellow or green mucus).
• Chest pain, especially when breathing or coughing.
• Fever and chills.
• Shortness of breath.
• Feeling extremely tired or weak.
• Loss of appetite.

Who is more likely to get pneumonia?

• People who smoke or vape.
• People with asthma or other lung conditions.
• Older adults and young children.
• People with weakened immune systems.
• People who have recently had flu or another respiratory infection.

Can pneumonia be serious?

Yes. Some cases are mild, while others need hospital treatment, oxygen or antibiotics (if caused by bacteria).

If you have severe difficulty breathing, blue or grey lips, or sudden confusion, seek emergency medical help (999 in the UK).

Can I ask you something?

Are you asking because you're curious, or because you or someone you know has a cough, chest pain or breathing difficulties?