Pneumonia is a lung infection. You may cough, run a fever, and have a hard time breathing. For most people, pneumonia can be treated at home. It often clears up in 2 to 3 weeks. But older adults, babies, and people with other diseases can become very ill. They may need to be in the hospital.

What causes pneumonia?

Germs called bacteria or viruses usually cause pneumonia.

Pneumonia usually starts when you breathe the germs into your lungs. You may be more likely to get the disease after having a cold or the flu. 

What are the symptoms?

• Cough. You will likely cough up mucus (sputum) from your lungs. Mucus may be rusty or green or tinged with blood

• Fever

• Fast breathing and feeling short of breath

• Shaking and ''teegh-chattering" chills

• Chest pain that often feels worse when you cough or breathe in

• Fast heartbeat

• Feeling very tired or very weak

• Nausea and vomiting

• Diarrhoea

How is pneumonia diagnosed?

Your doctor will ask you about your symptoms and do a physical exam. He or she may order a chest X-ray and a complete blood count (CBC). This is usually enough for your doctor to know if you have pneumonia. Your doctor may also test mucus from your lungs to find out if bacteria are causing your pneumonia. Finding out what is causing your pneumonia can help your doctor choose the best treatment for you.

How is it treated?

If pneumonia is caused by bacteria, your doctor will give you antibiotics. These almost always cure pneumonia caused by bacteria. Get plenty of rest and sleep, and drink lots of liquids. Do not smoke. If your cough keeps you awake at night, talk to your doctor about using cough medicine.

You may need to go to the hospital if you have bad symptoms, a weak immune system, or another serious illness.

How can you prevent pneumonia?

Experts recommend immunization for children and adults. Two different types of pneumococcal vaccines are recommended for people ages 65 and older. If you smoke, or you have a long-term health problem, it's a good idea to get a pneumococcal vaccine. It may not keep you from getting pneumonia. But if you do get pneumonia, you probably won't be as sick. You can also get an influenza vaccine to prevent the flu. You can also lower your chances of getting pneumonia by staying away from people who have a cold, measles, or chickenpox. You may get pneumonia after you have one of these illnesses. Wash your hands often. This helps prevent the spread of viruses and bacteria that may cause pneumonia.

https://www.webmd.com/lung/tc/pneumonia-topic-overview#1 

Ref: Pneumonia